User talk:Dolphin51/Archive 2

Work done on a parcel of air at the leading edge

To continue a discussion above: in earth's frame of reference, does a small area of the wing near the leading stagnation point do work on the parcel of air bearing on it? Mark.camp (talk) 22:13, 10 February 2009 (UTC)

Yes. In the frame of reference attached to the earth's surface, the velocity of the wing is the ground speed of the aircraft, and the velocity of the atmosphere is the wind speed/direction. Let's assume wind speed is zero. The small amount of air at the stagnation point is actually moving with the aircraft so it has a velocity equal to the aircraft's ground speed. The air at the stagnation point originally had velocity of zero, and KE of zero (because it was part of the atmosphere, and we are assuming the atmosphere was stationary — wind speed zero.) Now it has a velocity equal to the aircraft's ground speed, and a significant KE. Its increase in KE from zero to its value as part of the stagnation air is equal to the work done on it by the wing. Dolphin51 (talk) 23:33, 10 February 2009 (UTC)

In the steady state, I meant.

Mark.camp (talk) 21:05, 11 February 2009 (UTC)

Eugenics

I've posted a question for you at talk:Eugenics#The movement....   Will Beback  talk  22:34, 16 February 2009 (UTC)

Hi Will Beback! Thank you for the courtesy of alerting me to the new section at Talk:Eugenics. I have replied at Talk:Eugenics#The movement... Best regards. Dolphin51 (talk) 23:33, 16 February 2009 (UTC)

VMCG

Thanks for your note. The editor User:Reskin that added Vmcg copied the cites from the V-speed above and I checked for it in those refs and it wasn't there, either in TC AIM or in the cited FAR interpretation section, although it was in Peppler's book and already in the lower section under that. If he had cited it to FAR 25.149 than I would have left it. Thanks for locating it in FAR 25.149, I have cited it and moved the lower section entry up to the top section.

Good entry at Talk:Eugenics#The_movement.... I think Wikipedia is getting more reliable through efforts like yours! - Ahunt (talk) 00:43, 17 February 2009 (UTC)

Reviving Wikipedia:WikiProject Physics/Taskforces/Fluid dynamics

Crownest has expressed interest in reviving this. Since you were involved with the FD project (now converted into a taskforce), I'm wondering if you'd be a part of the Taskforce. The taskforce is undergoing a significant overhaul at the moment, and by the end of it, it should be fairly easy to get around and there should be a nifty compendium of useful tools for people interested in FD. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 10:54, 26 February 2009 (UTC)

Lift and the deflection of the flow

Hello Dolphin51. Can you take a look at Lift (force)#Newton's laws: Lift and the deflection of the flow. Especially w.r.t. my interpretation of Langewiesche, and perhaps you know some references to books etc. which use the approach John D. Anderson criticizes. I think you might know, because of all the discussions on the Bernoulli's principle article about this. Best regards, Crowsnest (talk) 00:04, 6 March 2009 (UTC)

Yes, I am happy to have a close look at the new section. I expect I can find a suitable citation or two in the next few days. Dolphin51 (talk) 06:47, 7 March 2009 (UTC)

I have now done some re-work of this section, and expanded the citation of Stick and Rudder. In the text attributed to Landau and Lifshitz is the sentence Consequently, the lift is directly related to the distribution of the vertical component of the flow velocity, ... Where this says component of the flow velocity should it be component of the flow momentum? The sentence is referring to a force (lift), and forces are related to momentum, not velocity. Dolphin51 (talk) 02:57, 13 March 2009 (UTC)

Great. I also rephrased the relation between lift and momentum: I put a simple one (but as far as I can see correct) in the main text, and the detailed one w.r.t. momentum flux in a footnote. Kind regards, Crowsnest (talk) 08:37, 13 March 2009 (UTC)

Glassy State

Yesterday (March 13, 2009), I submitted a fully referenced article entitled "Glassy State", describing in detail the physics of the glass transition and vitrification (solidification in the absence of cystallization).

Today, the article has vaporized...without a trace.

Any clues for me ????

logger9 (talk) 19:11, 13 March 2009 (UTC)

Hi Logger9. Your effort in creating "Glassy State" was commendable. Shortly after you completed your work User:RHaworth created a re-direct article so that anyone entering "Glassy State" would be re-directed to Glass. I see no evidence that RHaworth has contacted you to explain his (her) actions, so I have written to RHaworth and suggested that he (she) should do so.

After RHaworth re-directed "Glassy State" to Glass another user changed the re-direct to Vitreous.

To see this history of "Glassy State", enter "Glassy State" into the Wikipedia SEARCH engine and hit GO. You will be taken to Vitreous but the words "Glassy State" will appear in small, blue print near the heading "Vitreous". Select this small, blue entry and you will be taken to the re-direct page. Then select "History". Dolphin51 (talk) 01:27, 14 March 2009 (UTC)

My efforts were rejected by the primary outhor of "Glass" who states that: "I have reverted ... your contributions to the Glass article. Some sections, although cited were far too technical for wikipedia. Your efforts are appreciated but wikipedia is NOT a graduate level text book."

Is it possible that I could get a second opinion ?

The author seems to be more interested in the history of glass and his own ideas about the liquid/solid dilemma than any real science or mutual collaboration. He is extremely hostile about anything augmenting his private "domain".

logger9 (talk) 09:36, 14 March 2009 (UTC)

I see you are having some serious problems. Using the Talk page to discus the core of the problem is one strategy. That way, more than one user can get involved and that might temper the various views so that one extreme or self-oriented view does not prevail.

Also, I see you have been creating a large article and before you finish some other User jumps in and does some damage, not realizing you have not yet completed. The solution to this problem is to create a user sub-page for yourself. Many users (including me) have a personal sandbox that they can use for working up an article. This way, we can be certain our work is up to the desired standard before pasting it into a new article or adding it to an existing article. A personal sandbox is a user sub-page. My personal sandbox is User:Dolphin51/Sandbox. You can find detailed information about how to create a user sub-page at:
WP:SP#How to create user subpages.

Another advantage of a personal sandbox is that when you have finished your work you can write to other Users who also work in your subject field, alert them to the existence of your work in your sandbox, and invite their comment. It is unlikely that users will make major amendments to your work, or object to it, if they have been alerted to its existence and invited to comment when it was still in your personal sandbox. Good luck. Dolphin51 (talk) 00:36, 15 March 2009 (UTC)

Thanks immensely for your help...but for now they have rejected my work on the physics of the glass transition. They have their minds made up that glass is strictly a solid.

I give up !

logger9 (talk) 21:08, 15 March 2009 (UTC)

I do not think that the work of Logger9 is not appreciated at all, as seen on his talk page or on the glass talk page. There is just a communication problem. I hope Logger9 will not give up, based on initial opposition. Concerning the article Glassy state, all of its content should have just been added to the already existing article Vitreous. --Afluegel (talk) 21:34, 15 March 2009 (UTC)

Thanks Afluegel. Logger9 is an enthusiastic newcomer, and he (she) is learning fast. I and others are encouraging him to make use of Talk pages prior to making major changes to articles. I am also encouraging him to start a personal sandbox so he can create new text without interuption, and then show it to other users in his field and ask for their comments. Dolphin51 (talk) 03:15, 16 March 2009 (UTC)

I cannot thank you enough for re-directing my efforts to the implementation of a user subpage Logger9: Physics of Glass. I am fully confident that we may still be able to work something out with my proposed material on the physics of glass and the glass transition. == logger9 (talk) 18:48, 16 March 2009 (UTC)

Lift (force) intro

Hi Dolphin51! I left some comments on User_talk:Dolphin51/Sandbox. Best regards, Crowsnest (talk) 17:18, 20 March 2009 (UTC)

Static pressure

Hi Dolphin51. I saw you changed the section order in Static pressure. I learned (being attended to it by others), that there is a preferred order of the standard appendices at the end of an article, see MOS:APPENDIX. Although the MOS is not very clear about it, the Notes (as a separate section) seem to precede the References. Although also sections titled "Notes and References" or "References and notes" occur (with possible subsections "References" and "Notes"). Kind regards, Crowsnest (talk) 11:42, 24 March 2009 (UTC)

Thank you for alerting me to WP:Layout and, in particular, MOS:APPENDIX. I was not previously aware of this information. I am happy to make my work conform to this layout so I will re-visit Static pressure and make the necessary adjustments. Dolphin51 (talk) 21:47, 24 March 2009 (UTC)

Bedrock Gardens

Hey Dolphin51... I did not see your comments on my user page until this last note. Thank you for following up on it. I followed all your suggestions, all very appropriate. I listed this as a minor edit, since no changes in content made. Right? Also what would it take to improve it an A quality article?Zipity11 (talk) 17:34, 3 April 2009 (UTC)

d'Alembert's paradox

Hello Dolphin51. Thanks for your help with d'Alembert's paradox! If you like to: can you also have a look at the section Inviscid separated flow: Kirchhoff and Rayleigh, which I also wrote. I am particularly keen on having this article correct, because of the controversies (see talk page, and Talk:Navier–Stokes existence and smoothness). Best regards, Crowsnest (talk) 08:04, 9 April 2009 (UTC)

Yes, I am very happy to look at this new section. It may be a couple of days before I get back onto the www. Dolphin51 (talk) 22:40, 10 April 2009 (UTC)

Your new information in this Section is very good! I have reviewed it and made a number of editorial changes. I tried to avoid any change to the technical content but if I have inadvertently made such a change please correct it.

Cavity flows appears as a red link. I was unable to find any article resembling cavity flows so I assume your red link was deliberate. Best regards. Dolphin51 (talk) 01:14, 14 April 2009 (UTC)

Thanks! It looks better now. -- Crowsnest (talk) 01:19, 14 April 2009 (UTC)

Can you take a look at the Physics assessment on its talk page. It is classified as "start", which seems not correct any more to me. Further I hope someone will write the "cavity flow" article: I will ask for it. -- Crowsnest (talk) 02:16, 14 April 2009 (UTC)

Hi Dolphin51. Many thanks for your work on the intro. I will give it some additional tweaks, since some edits changed meanings (e.g. dropping "constant velocity": time-varying potential flows create in-line inertia forces).

Also thanks for re-assessing the article as B-class. As far as I understand, the common route is stub-start-C-B-GA-FA (eventually hopping through this), and not many articles are asked for A-class review. For instance in the fluid dynamics taskforce we have no A-class articles, but do have GA and FA articles. Kind regards, Crowsnest (talk) 18:05, 15 April 2009 (UTC)

If my edit introduced some changes to the technical content please go ahead and restore the correct meaning. I changed the sentence the drag force is zero on a body moving with constant velocity through the fluid to remove the reference to constant velocity because drag does not rely on constant velocity; it also occurs on an accelerating body. You may be able to restore your original intention in such a way that drag does not appear to be only a constant-velocity phenomenon. Regards. Dolphin51 (talk) 00:34, 16 April 2009 (UTC)

Equations: Help !

Could you please help me to set up my square roots here ? -- logger9 (talk) 23:46, 12 April 2009 (UTC)

I'm happy to help, but it looks like Crowsnest has already done a fine job on your equations. Information about displaying math formulae is available at WP:MATH. Best regards. Dolphin51 (talk) 12:32, 13 April 2009 (UTC)

'Do you like dolphins, Dolphin51? I do. I also love marine biology, cetology, and scuba diving! I believe in creation though, and not in atheism. Where did everything come from if there isn't a God?''''Please answer me!!!Diver62 (talk) 16:18, 16 July 2010 (UTC)

Hi Diver62! Welcome to my Talk page. Yes, I like dolphins, they are my favourite aquatic mammal.

I don't have a problem with people believing in creation, providing they are critical thinkers rather than obedient thinkers. Critical thinkers apply their minds diligently to ideas and questions, and they base their conclusions on honest reasoning. I suspect many people, particularly young people, who believe in creation do so as a result of being obedient thinkers rather than critical thinkers - they believe what is put before them because they want to be obedient.

The origin of the universe is largely a mystery - scientists talk about the Big Bang. If people want to explain the origin of the universe by saying God created it, I don't have too much problem with that. (It isn't too far removed from saying there was a Big Bang.) What I really object to is that many millions of people then go on to say something like God created it, and to find out more about God you must read the Bible (or the Torah or the Koran) What follows is a lot of man-made explanation and man-made rules that are broadcast as being the word of God. God may have created the universe but I'm sure he had nothing to do with the rules and interpretations written down through the centuries to make many lives very miserable, especially considering the men who wrote those rules and interpretations, and others who followed after, promoted their work by saying This is the word of God. These writings are not the word of the God who created the Big Bang. These writings are the words of men.

Be a critical thinker; not an obedient thinker. Best wishes. Dolphin (t) 11:25, 21 July 2010 (UTC)

Quality scale

In response to your question at Wikipedia:Editor assistance/Requests, you can find all the quality classes here. OnHoliday 10:16, 14 April 2009 (UTC)

Many thanks. Dolphin51 (talk) 13:13, 14 April 2009 (UTC)

Static Pressure

Stagnation pressure is defined at every point of a compressible flow, not at stagnation points, Pstag/P = [1 + 1/2(k-1)Ma^2]^[k/(k-1)].

I take your point that maybe, in a general context this does not apply, but it is not always true that you need a stagnation point to find the stagnation pressure of a fluid flow. I've always taken it to mean, if we stagnated this flow at this point, this would be the pressure (or temperature or density or speed of sound, etc), or this is how it has been presented to me at least. - The Talking Sock talk contribs 14:51, 14 April 2009 (UTC)

Hi Sock. Thanks for your prompty reply. WP:Verifiability shows that it all depends on what sources of information we are using to ensure verifiability. Different books and websites inevitably use slightly different terminology, and different ways of explaining things. We can insert in Wikipedia just about anything, provided it is supported by references and in-line citations that confirm our addition is independently verifiable; and provided it is presented from a neutral point of view.

Both Stagnation point and Stagnation pressure were seriously lacking in references and in-line citations. I have made some additions and changes, and cited L.J. Clancy's book Aerodynamics. In Aerodynamics, Clancy uses stagnation pressure in the context of the static pressure at a stagnation point. He uses total pressure in the context of the Bernoulli constant, defined and existing at every point in a flow field. He uses pitot pressure in the context of the static pressure in a pitot tube. As you know, all these three are numerically identical in incompressible flow, and also in compressible flow providing there are no shock waves in the vicinity.

Pitot pressure is a specialist term. We probably both agree that it would not be reasonable to write that pitot pressure exists everywhere in a flow field - it only exists inside a pitot tube. No pitot tube, no pitot pressure. Similarly, Clancy and I take the view that stagnation pressure is also a specialist term, and it would not be reasonable to write that stagnation pressure exists everywhere even if there is no stagnation point present.

If you are able to cite a suitably reliable and authoritative source for a statement that stagnation pressure is defined at all points in a flow field you are at liberty to insert that in Wikipedia to show that there is a second meaning to the word. However, you should be careful not to unnecessarily confuse the reader. Happy editing. Dolphin51 (talk) 05:19, 15 April 2009 (UTC)

Maybe it's the idiosyncrasies of my text book (by F.M. White). He's a bit of an odd character, I mean, who writes a thick inaccessible fluid mechanics text with a conversational tone?... ; ) Anyway, thanks for taking the time to get back to me on this subject. I will look at other sources before i inject anything from this odd (though reliable and authoritative) text.

-The Talking Sock talk contribs 13:10, 15 April 2009 (UTC)

New Cl graph

Hi, and thanks for the welcome. I am concerned that the Cl vs AOA graph promulgates the wide misconception about what happens to lift when a stall occurs. It does not actually drop as shown in the graph. On the talk page on stall I give a ref -if you would like to look at it -but I can't find a new graph to replace the incorrect one. What to do? I could grph one up or is it acceptable to grab an image from the Sandia National labs research paper on this? I suspect the latter would violate copyright but I'm really not sure. Hope you can advise :) Here a the second hand ref that leads to the original work: http://www.aerospaceweb.org/question/airfoils/q0150b.shtml Cheers MarkC (talk) 04:23, 23 April 2009 (UTC)

Hi Mark. Your point is a good one. There is a less offensive graph here. It might be preferable to the present one.

The latest version of the offending graph on Stall (flight) was produced by User:Interiot. One approach to the problem is to write to him on his talk page, explain the problem, give him the link to the aerospaceweb site and ask him to up-date the graph. Before trying a second option, let's see how successful this is. Happy editing. Dolphin51 (talk) 05:27, 23 April 2009 (UTC)

Ok I left him/her a message and the ref. CheersMarkC 10:05, 23 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

Re refs. yes, i'm intending to ad some refs. I had to go flying in the middle of the edits tho :) Cheers MarkC 09:18, 25 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

Tilde help

Hi, I typed 4 tildes in the talk page on aeros and this is what is diplayed: MarkC 04:51, 29 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

It put in my user name but why does it say "unsigned comment added by mbcannell"? Why does it say unsigned when it just signed it for me? MarkC 05:50, 29 April 2009 (UTC) —Preceding unsigned comment added by Mbcannell (talk • contribs)

Mysterious indeed! The suggestion from Crowsnest on your User talk page looks like a good one. I think Crowsnest has found the root of the problem. However, if that doesn't work, try asking the question at Help desk or Editor Assistance Requests. Dolphin51 (talk) 09:56, 29 April 2009 (UTC)

FIXED!!! Thanks guys!

Aerobatics

ccd from Aerbatics talk: J+D, How about this. In the lede we describe how the rapid changes in direction lead to high forces on plane and pilot. This means that aero. planes must be structurally stronger and we give typical structural g-limits for both normal and aerobatic planes. Don't forget glider aeros. Then describe how pulling a loop requires about 3.5g in a (say) an aerobat or citabria/decathalon which is close to the limit for a normal cat plane (+4g). We note that more extreme manouvers and faster planes require higher forces. in a new section called perfomance, we describe phsyiological conditing reuired for top pilots and planes. I've found a good research paper [2] that describes changes in VO2 and HR during measured g excursions in experienced pilots in CAP 10 and CAP231 aircraft. We also desribe why/how aero planes are different. Finally we talk cerification requirements? Any other ideas or shall we divvy these tasks up? Cheers MarkC 20:36, 29 April 2009 (UTC)

MarkC (talk) 20:43, 29 April 2009 (UTC)

Stall (flight)

Hi Mark. On 1 May you edited Stall (flight) to add a comment about the commonality of stalls after takeoff. You called these stalls departure stalls and you cited the FAA Airplane Flying Handbook, Chap 4, pp.11-12. In the context of the stall, departure usually refers simply to a departure from controlled flight at any height, and any phase of flight. The notion of departure from controlled flight is even mentioned explicitly on Wikipedia at Departure.

I haven't been able to find mention of departure stalls after takeoff at pages 11-12 of Chap 4. Could you check your edit on this subject to ensure that all you have written is covered by your cited sources? Thanks. Dolphin51 (talk) 11:36, 3 May 2009 (UTC)

That's not my terminology. I just moved the whole paragraph. Please check and revise -I don't know who wrote it. Thanks MarkC (talk) 09:01, 4 May 2009 (UTC)

Checking, the term "departure stall" is used in the context of a high pitch/high power stall which is most likely to be experienced on climb out ... see http://books.google.co.nz/books?id=GKMSsue-JW0C&pg=PA74&lpg=PA74&dq=departure+stall&source=bl&ots=uhFdRKX6TC&sig=7TeWbpSN5b2tvbM5hJGy228i7sc&hl=en&ei=jq_-Sc7SJajmtgOqreTxAQ&sa=X&oi=book_result&ct=result&resnum=8

so it is correct -at least in the USA -but its not my writing :-) . Cheers MarkC (talk) 09:07, 4 May 2009 (UTC)

Vorticity

Hi Dolphin51. To my opinion it is not very useful to change omega's into zeta's or the other way around, since both are used frequently. There is no preferred symbol, like p is for pressure. And Wikipedia does not set the standards. Consensus with respect to one article, where different notations are appearing in different sections, is useful. E.g. in Conservative vector field both u and v are used for velocity. But this consensus does not transfer to other articles. It depends on what symbols are available, e.g. in free surface flows zeta is often used for the surface elevation, so then it is natural to use omega for vorticity; or if you use omega for angular frequency, you can use zeta for vorticity. For velocity also u, v, U and V are used. To my opinion, it is like with the varieties of English spelling: keep the notation as it has been introduced. Best regards, Crowsnest (talk) 07:22, 6 May 2009 (UTC)

Hi Crowsnest. I agree with what you have written, particularly your point about similarity with varieties of English spelling.

Vorticity appears in both Vorticity and Conservative vector field, but there is only one in-line citation to the mathematical definition of vorticity. That is a citation to Clancy's Aerodynamics in Vorticity. (Clancy uses zeta for vorticity throughout his book.) In Conservative vector field all references to the mathematical definition of vorticity are unsourced. If another in-line citation is given in the future, and it is a citation to a source that uses omega, I would be comfortable with that. In the absence of any alternative citation for vorticity I believe Wikipedia is relying on the one citation of Clancy's Aerodynamics that appears in Vorticity. (Clancy uses zeta.)

Vorticity and Conservative vector field are both poorly served by in-line citations so I have added the Morefootnotes banner to both of them. Best regards. Dolphin51 (talk) 12:31, 6 May 2009 (UTC)

Hi Dolphin51. I added a ref to Batchelor, which is a renowned one using omega for vorticity. Best regards, Crowsnest (talk) 13:05, 6 May 2009 (UTC)

And in Conservative vector field I added one for zeta. -- Crowsnest (talk) 19:22, 6 May 2009 (UTC)

Thanks for those citations. I have restored omega as notation for vorticity in Conservative vector field, and added a comment that zeta is a common alternative notation. Seeing Batchelor uses omega it would be useful if citation of his book was added to the paragraphs on Irrotational flows in Conservative vector field. (Would it be reasonable to use Batchelor as the citation for the opening sentence? It is presently unsourced.) Best regards. Dolphin51 (talk) 03:32, 7 May 2009 (UTC)

There is less or no need for citations in the lead, provided the statements made are uncontroversial and repeat themselves (or summarize what is) in the sections of the article, see WP:LEADCITE. To my opinion the focus should be on adding references to the sections, i.e. "Path independence" and "Irrotational vector fields". -- Crowsnest (talk) 07:44, 7 May 2009 (UTC)

Further I am reluctant to add refs, since this is a math article. It is a bit funny to primarily refer to aerodynamics and gasdynamics books there. The more, since the reasoning of mathematicians here seems to be reverse to the one used by physicists: in maths a conservative vector field is defined to be the gradient of a scalar field, while in physics a force is called conservative if the work by that force is independent of the path, and subsequently as a result it is shown this is the case when the force is the gradient of the potential energy. -- Crowsnest (talk) 09:22, 7 May 2009 (UTC)

Revert big changes to Aircraft principal axes, Yaw Axis, etc. by User:Juansempere?

Hi Dolphin51 and Crowsnest,

I saw some recent mergings of Yaw Axis, etc. made by User:Juansempere and I think it's created a lot of error. I'd like to just revert the lot of it. I'm bold, but not bold enough to do such a thing without concurrence from "bigger heads" (you guys and others you think should be consulted). I also don't know if I know how to do it properly anyway. I made a few edits myself before I realized how much chaos and error had been created, those edits should be reverted too of course. Could you guys take a look at it and see if you agree that it should just all be reverted? (With kindness toward User:Juansempere of course.)

Gummer85 (talk) 04:51, 19 May 2009 (UTC)

I already undid my edits to Aircraft principal axes to get the ball rolling (and also because I don't want to be associated with this article and the long slow slog up the hill to correctness it would need). --Gummer85 (talk) 05:40, 19 May 2009 (UTC)

Dolphin51, thanks for the edits you made to fix my sandbox by the way. I was away for some weeks and I didn't realize I was "broadcasting". :-) --Gummer85 (talk) 05:05, 19 May 2009 (UTC)

On the Talk:Aircraft principal axes page I have raised a new section and invited Juansempere to talk about what his edits have been aimed at, and what he plans for the future. I have also left a message on his User talk:Juansempere page alerting him to my request on the Aircraft principal axes talk page. Dolphin51 (talk) 07:13, 19 May 2009 (UTC)

Flaps (aircraft)

Hello!

I think we may be trying to convey different sides of the same coin. I agree with you regarding our airplane in the pattern scenario. The point I am trying to make, is all else being equal, the lift will indeed increase. Please permit me:

Assume our airplane in the circuit is in steady level unaccelerated flight (say, downwind for landing). The pilot deploys flaps partially. Immediately, the airplane experiences a resulting upward "wafting" effect. In order to maintain altitude, the pilot must counteract this with other control efforts, including changing airspeed and/or pitch.

This wafting effect is explained by the shifting of the lift-curve on a C_L vs alpha chart.

It seems to me that we are trying to make similar explanations, but emphasizing different facets of the same coin. Your thoughts? Jadias (talk) 05:18, 26 May 2009 (UTC)

Hi Jadias. Thanks for your comprehensive reply.

The aerodynamics of the fixed-wing aircraft are a little more complex than given in your description. When flaps are extending two important changes are taking place. One is that the pitching moment coefficient on the wing changes and increases the nose-down pitching moment on the aircraft. Simultaneously the downwash behind the flap increases and changes the downwards lift generated by the horizontal stabilizer, causing a decrease in nose-down pitching moment on the aircraft (or an increase in nose-up pitching moment on the aircraft.) These two changes work in opposite directions. Whichever is stronger will dictate the pitch change on the aircraft. If the pilot does nothing to counteract the pitch change it will cause a change in angle of attack and that will cause a change in lift coefficient.

In low-wing aircraft and T-tail aircraft the change in pitching moment coefficient of the wing is usually stronger than the change in downwards lift on the horizontal stabilizer. In these aircraft, as flaps are extending there is a tendency for the nose to pitch down, angle of attack reduces, and the pilot responds by trimming nose up or pulling back on the elevator control.

In high-wing aircraft the change in downwards lift on the horizontal stabilizer is usually stronger than the change in pitching moment coefficient on the wing. In these aircraft, as flaps are extending there is a tendency for the nose to pitch up, angle of attack increases, and the pilot responds by trimming nose down or pushing forwards on the elevator control.

In some aircraft, as flaps are extended from the cruise position the change in pitch occurs in one direction, but by the time the flap approaches full-landing position the pitch occurs in the opposite direction. Somewhere in between there is no change in pitch for a change in flap position.

It is not possible to accurately summarise these transient effects by saying that extending flaps increases lift. In my view, the best way to summarise the changes is to say that extending flaps reduces the stalling speed and increases drag.

Cheers. Dolphin51 (talk) 23:32, 26 May 2009 (UTC)

Interaction between streamlines of "inviscid" fluid on Bernoulli talk page?

Here:

Talk:Bernoulli's_principle#Interaction_between_streamlines_of_.22inviscid.22_fluid.3F

This is still a puzzle to me. I've loooked but can't find an explanation of if or how such theoretical interactions could take place. Jeffareid (talk) 10:54, 17 June 2009 (UTC)

Thanks for the welcome

Hi Dolphin51! Thank you very much for your welcoming message to me, a mere newbie. Like you, I love Wikipedia because it promotes free knowledge, so I aim to participate actively in it. I'm happy to know that if I have any questions, I can come to you. Thank you.--Wise Sage150 (talk) 00:23, 18 June 2009 (UTC)

Glass Transition

Have you checked this out ? -- logger9 (talk) 21:57, 29 June 2009 (UTC)

Hi Logger9. I have looked quickly at the edits immediately before your 21:57 29 June posting above. A lot was happening on the page on 29 June!

The topic is well outside my area of expertise so I'm afraid I can't offer any meaningful comments at this stage. If you clarify what edit in particular, and the nature of the problem, I may be able to contribute constructively. Best regards. Dolphin51 (talk) 12:41, 30 June 2009 (UTC)

Coordinated flight

Thanks for your note. Being unreferenced is one thing, but that section was totally incomprehensible! I hate to think of some non-pilot trying to figure it out. That article still needs some work, so feel free to dive in! - Ahunt (talk) 12:57, 3 July 2009 (UTC)

Image creation

Somewhere along the line, I recall someone offering their services for creating basic images which could be uploaded into Wiki articles. Do you have any idea who that may have been ? -- logger9 (talk) 03:25, 16 July 2009 (UTC)

Hi Logger9. I don't recall the identity of someone offering their services, but I am aware of the work done by User:Arpingstone in the field of photography. On his Talk page I have asked him to offer you a few suggestions. He may offer to help you. Best regards. Dolphin51 (talk) 11:33, 16 July 2009 (UTC)

At here Adrian Pingstone has offered to provide some written information about photographs. Dolphin51 (talk) 05:38, 17 July 2009 (UTC)

Adrian Pingstone has provided details about using photographs on Wikipedia. See User:Arpingstone/Sandbox. Dolphin51 (talk) 13:13, 17 July 2009 (UTC)

English fine-tuning

My sincere thanks for "fine-tune" my user page introduction. I didn't notice your contribution until recently. I really appreciate that! Best wishes. RobertoRMola (talk) 22:36, 6 August 2009 (UTC)

Re: civility

I have just given a detailed reply in the talk page. I think that if you read the detailed chronology of the events and also keep in mind the dangers of young studets in high school and the first years at university to wrongly learn something, you'll accept that, on balance, what I did was correct.

The expertise of user quantumechanics had, like it or not, become a major relevant issue at that point, not in the least because he was effectively claiming expertise (by arguing that he has a book, and because he thinks book says that something his edit is now supported by the citation e gives). Then after arguing with him over and over again, it was time to ask him to put up or shut up. Count Iblis (talk) 14:10, 12 August 2009 (UTC)

Thank you. I have replied at User talk:Count Iblis#Civility. My allegations relate to your behaviour towards Quantumechanic, not the technicalities of Entropy or who should set the direction of the article. Wikipedia's Code of Conduct is the fourth of its five pillars. These five pillars override all considerations of technical content. Dolphin51 (talk) 03:35, 13 August 2009 (UTC)

I don't agree that I was uncivil. Uncivility is not merely using certain types of words, it is using these words when it is not appropriate. As I explained in detail, it was very appropriate for me to ask user Quantumechanic to explain himself. When you make a business agreement with someone, but you turn out not to be reliable, then when that is established beyond a reasonable doubt, it would be perfectly reasonable for your business partner to raise certain issues about you, that under normal circumstances would not be appropriate to raise.

E.g., the simple fact that you are a bit late with certain deliveries should not provoke an immediate suspicion that you are a fraud. But if proof of fraudulent activity emerges, then it would be perfectly reasonable for your business partner to put some facts about your conduct on the table that are hard to explain otherwise.

Now, if you say that I as an involved party should not sit in judgement, then I would disagree on the grounds of a lack of a Wiki-Noticeboards on which I could raise my concerns about user Quantumechanic. There does exist a noticeboard for reporting incivility, for edit warring, etc. etc. but not for notifying the wiki community that someone is editing in nonsense into science articles. Count Iblis (talk) 13:41, 13 August 2009 (UTC)

Please do not post incidents in multiple forums. Although various locations exist in order to resolve situations, it is best to choose the correct location once, and allow all discussion to take place there. Although you may be directed to another forum by admins or other moderators, you will at least be directed to the best forum. Please note that at least one of the postings will be closed at this time in order to prevent fragmented discussions. Thank you. (talk→ BWilkins ←track) 12:21, 15 August 2009 (UTC)

Echoing the above, I have removed your communication with me on my talkpage and reposted it at WQA, in order to keep the discussion in one place. Elen of the Roads (talk) 11:08, 17 August 2009 (UTC)

Hello

You may wish to see Wikipedia:Sockpuppet_investigations/Satanoid. Irbisgreif (talk) 06:18, 25 August 2009 (UTC)

Thank you. I have read the sockpuppet report. Dolphin51 (talk) 12:00, 25 August 2009 (UTC)

Requested change in heading.

I've changed the heading in which I inappropriately named a user to "Keeping the article referenced". I apologize, and I thank you for pointing this policy out to me. Rick Norwood (talk) 12:33, 27 August 2009 (UTC)

WT:CIVIL

Hi Dolphin, I have a question about one of your edits earlier in the month at WT:CIVIL. - Dank (push to talk) 18:27, 27 August 2009 (UTC)

I agree that all Users should be treated with respect, and treat other Users with respect, at all times. My addition about condescending language and the absence of a rank structure was intended to highlight one example of how Users sometimes treat others disrespectfully without realizing the significance.

When parents are talking to their children they often do so in a way that reflects the authority gradient between parents and children. This is entirely reasonable, but if one adult were to talk to a second adult in the same way it is likely to be perceived by the second adult as condescending. The second adult feels uncomfortable and is likely to complain about not being treated with respect.

Legitimate authority gradients exist between teachers and students, police officers and members of the public, event organizers and members of the audience, employers and employees. The military and police forces have clearly-defined rank structures to ensure the appropriate authority gradient exists and is respected. These legitimate authority gradients are commonly manifested by use of language which would be counterproductive if the authority gradient did not exist. In the absence of a legitimate authority gradient this language is likely to be perceived as condescending, and it is counterproductive because it de-motivates the audience from performing to the best of their ability.

Wikipedia has been established as an institution without any rank structure, so there is no legitimate authority gradient. Wikipedia appoints Administrators to carry out defined administrative tasks, but those Administrators are granted no rank. There is no authority gradient between the most experienced User/Administrator, and the inexperienced newcomer. Consequently language that is assertive or conceited will only be perceived as condescending, regardless of who uses the language. Condescending language is very likely to lead to angry or uncivil responses as aggrieved Users defend their dignity. The original writer may expect a deferential response so the angry or uncivil response is likely to inflame the exchange to a new level of assertiveness or condescension, provoking an even angrier response. The only ideal solution is to avoid the condescending language from the start.

Treating others with respect at all times is a noble objective. However, for some Users it is not as easy as we might imagine, perhaps partly because they have so little recent experience in an environment devoid of authority gradient. I hope that an explicit reminder of the absence of a rank structure, and the consequent need to avoid language which might be perceived as condescending, will help some Users adjust to Wikipedia. It is also useful having that explicit mention at WP:Civility#Engaging in incivility so Users can point to it when cautioning other Users about their use of inappropriately assertive language. Dolphin51 (talk) 00:48, 28 August 2009 (UTC)

Thanks for the welcome

It is very nice to have someone welcome you on your very first day. Thanks.

Today I finally got up the nerve to change a wikipage! I felt strongly that the material there was incorrect and that I have significant expertise in the area. I read several comments in the discussion page first. It seemed others held similar opinions, but were not bold enough (see, I already learned something about wiki today ;) actually to edit the page. So I went for it. I'm talking about the page entitled "Coanda Effect." When I get more experienced, I expect I will be able to insert an appropriate link to the location, but I'm sure you can find it by searching.

I realize that as a newcomer I may have made some obvious blunders in my approach. If so, I'd be more than happy to learn how to do things right. Feel free to leave comments on my user page.

Thanks again,

-Kim

Kimaaron (talk) 05:47, 9 September 2009 (UTC)

Hi Kim. You are off to a flying start on Wikipedia! Your contribution on Coanda effect is very welcome because there is a lot of misinformation out there which dismisses Bernoulli's principle as an explanation for lift on an airfoil, and insists Coanda effect is the only correct explanation! I was pleased to see another User (you!) who doesn't regard Coanda effect as the explanation for all observable phenomena in fluid dynamics.

Part of the fun of Wikipedia is discovering new things, and teaching yourself how to do it. Don't be hesitant about trying new things - have a look at WP:BE BOLD. Also, there is the Wikipedia sandbox where everyone is encouraged to try things and no-one cares if some of it doesn't work properly.

Happy editing. Dolphin51 (talk) 10:39, 9 September 2009 (UTC)

When I logged in, it told me there was a message for me here. Did you do anything to make that happen or is it just automatic? Thanks.

-Kim

Kimaaron (talk) 14:29, 10 September 2009 (UTC)

Hi Kim. After I replied to your message immediately above, I wanted to alert you to check my Talk page to see my reply. I went to your Talk page and posted a tag saying {{talkback|Dolphin51}}. That tag produces the smart coloured banner. It doesn't happen automatically. Regards. Dolphin51 (talk) 12:33, 11 September 2009 (UTC)

Hullo... Just want to say I appreciate the welcome (you are the only one to welcome me)... however, I'm not new to Wikipedia, or to updating or discussion pages. :o) And you suggested I use my signature, which I always always do... so if it was missing then someone else edited it out. :o) Cheers! --gobears87 (talk) 21:52, 19 November 2009 (UTC) [if there is no sig there, someone "stole" it!!!]

Hullo Gobears87. Your signature is still there, just where you put it. Best regards. Dolphin51 (talk) 02:00, 20 November 2009 (UTC)

Thanks again. Particularly appreciate those links, haven't used most yet but haven't had time to learn all the seemingly infinite ways of doing and adding and talking on Wikipedia. It could be a full-time job! :) Cheers --gobears87 (talk) 11:36, 28 November 2009 (UTC)

Wing configuration

As a member of the Physics fluid dynamics taskfoce with an interest in aircraft design, would you mind looking at Wing configuration with a view to its assessment against your project/taskforce quality scale? Thanks. GraemeLeggett (talk) 11:47, 11 September 2009 (UTC)

Fabulous graphics! I will refresh my memory about the various ratings for quality and importance, and form an opinion about where Wing configuration stands at present. Regards. Dolphin51 (talk) 12:40, 11 September 2009 (UTC)

AfD nomination of List of fixed-wing aircraft without flaps

An article that you have been involved in editing, List of fixed-wing aircraft without flaps, has been listed for deletion. If you are interested in the deletion discussion, please participate by adding your comments at Wikipedia:Articles for deletion/List of fixed-wing aircraft without flaps. Thank you.

Please contact me if you're unsure why you received this message. - Ahunt (talk) 23:29, 10 October 2009 (UTC)

Re: Don't bite the newcomers

Thank you for talking to me before reverting. Consider the following: User:Mmnbv21 added a just published article, on a very specific topic (I've looked it up) into several articles, without explaining the reason or motivation. Those adds into "further reading" did not add any new information. Mere adding a link to one primary source (not even a review) when thousands others are published on this topic, does look suspicious. You should know better than I that wikipedia is not a link collection. Regards. Materialscientist (talk) 00:29, 16 October 2009 (UTC)

Thanks, I left a note on the User:Mmnbv21 talkpage. Regarding Colloid, most other "further reading" items are books or reviews. It takes time to cleanup "further readings" in that 1000+ articles I watch (one has to find and quickly analyze every article), but I'm trying my best. If you are scientist or have scientific journal access, your help is more than welcome. Materialscientist (talk) 01:05, 16 October 2009 (UTC)

Bernoulli

You are right about [1] of course but there is some US professor who doesn't understand Bernoulli and teaches it is wrong, with a demonstration using an air jet and a pressure meter . The point is I guess that Bernoulli only applies along a flow line than the demonstration he gives involves a jet in free air. It is perhaps OR but perhaps we could improve the wording on the flow over a wing to include the obvious point that the flow under and over the wing originated as adjacent flow lines in free space and so had the same starting pressure? --BozMo talk 11:04, 23 October 2009 (UTC)

There have been various authors dismiss the relevance of Bernoulli in understanding lift on an airfoil. These have been authors of introductory books for student pilots and newcomers to aviation. These authors usually advocate an explanation of lift based on Newton’s Third Law of Motion rather than Bernoulli. The two most recent authors have been David F. Anderson and Scott Eberhardt who wrote Understanding Flight. I did quite a bit of work on this subject a couple of years ago. You can read my summaries at Talk:Bernoulli's principle/Archive 2#Understanding Flight.

There has been a lot of vandalism at Bernoulli's principle and Lift (force) by anonymous editors who have been keen to erase all mention of Bernoulli when explaining lift. The recent example of vandalism is the first for many months. I think we are winning the battle! Dolphin51 (talk) 11:23, 23 October 2009 (UTC)

Ok. I have seen and reverted this tendency on a few related articles [2] and a while back had an argument with a "Bernoulli is wrong" editor who sent me to some professors page somewhere but I had not seen the books. --BozMo talk 11:35, 23 October 2009 (UTC)

Yes, I have seen that approach before. When someone refers us to a professor or high-profile author, without actually understanding the issue themselves, it is merely an appeal to authority and not sound philosophically! Dolphin51 (talk)

Wingtip vortices

See diff.

Hello. My username is "graysoc." I am no engineer, but you should know that most, if not all, of the aerodynamics text books state that the greatest wingtip vortices come from heavy, clean, and slow aircraft. This makes sense to me because the "clean" wing allows spanwise flow across the entire wing, and thus the tip vortices are stronger. A flap does increase lift, but it also breaks up some of the flow, so the tip vortex isn't as strong as it could be otherwise. With flaps, there will be several vortices, not just one at the wingtip. Here is a discussion by a few pilots. http://www.pprune.org/tech-log/353898-strongest-wing-tip-vortices-when-slow-clean-heavy-but-why.html

I'm not at home right now, but out flying a trip, but when I get home I'll find the references for you. The aerodynamic handbook for naval aviators discusses this, I believe. I'm pretty sure that the NASA flight research on this topic confirms my assertion. Again, I don't have the written word in front of me, but I will when I get home.

http://www.slideshare.net/aulger/ground-lesson-3-wake-turbulence —Preceding unsigned comment added by Graysoc (talk • contribs) 19:27, 25 October 2009

Thanks Graysoc. I have checked FAA Advisory Circular AC 90-23F Aircraft Wake Turbulence and I concede that in sub-section 5 it states that the greatest vortex strength occurs when the generating aircraft is heavy-clean-slow. Unfortunately it makes no attempt to explain the link between vortex strength and wing flap configuration. This is a pity because saying vortex strength is greatest in the clean configuration is counter-intuitive and deserves a clear explanation. The reason I say it is counter-intuitive is that there is a strong and clear relationship between trailing vortices and induced drag. Induced drag increases as wing flaps are extended, and it decreases as they are retracted. (That is why wing flaps are retracted after takeoff, and they remain retracted throughout the cruise.) So when the Advisory Circular states that vortex strength is greatest in the clean configuration it demands an explanation as to what the author has in mind. I look forward to seeing your other references. Best wishes. Dolphin51 (talk) 23:59, 25 October 2009 (UTC)

(I'm not familiar with talking on this site like this, so I hope I'm doing this correctly)

My understanding about flap configuration is that while they do increase lift, especially in the first couple of notches, the flaps primarily provide drag in the landing configuration. This drag allows for the engines to be spooled up during a decent, but keep the relatively slow airspeeds necessary for landing. My intuition on this is that a clean wing will require a higher angle of attack to get the same amount of lift as wing with flaps extended, and thus the vortex is stronger. That is why I do not feel that it is counter-intuitive. Higher angle of attack = larger induced drag = more vortex. Flaps may have more lift (more induced drag), but because the increased lift is not generated across the entire wing, but only where the flaps are located, the net increase may not be greater than if the wing is clean at the same airspeed. The overall angle of attack for the wing is lower, and thus the vortex is not as strong.

Imagine an aircraft taking off, and shortly after departure the pilot retracts the flaps at 160 knots. My aircraft can fly at that airspeed "clean," though, honestly, we would be rapidly accelerating. Imagine us in a static situation, stuck at 160 knots. One clean, one with flaps. Our angle of attack as the flaps retract will increase to maintain the same climb rate or altitude because we are losing some of the lift from the flaps. Because we are generating the same lift "clean" as we were with the flaps, with a higher angle of attack, we surely are creating a stronger vortex than a few seconds prior when we had one notch of flaps in at the same airspeed. The fact of higher angle of attack, combined with the fact that the airflow will be smoother towards the end of the wing with no interruption from the flaps, seems to necessitate stronger vortices.

In the landing configuration, there is just so much flap buzz and disruption of airflow due to the high drag of full flaps, I cannot wrap my brain around that configuration creating a stronger vortex than a departing clean aircraft. Those full flaps also reduce the overall angle of attack of the wing, which surely reduces the overall induced drag. I'm sure there is increased induced drag at the edge of each flap, but those flaps do not run the width of the entire wing.

Of course, these are pure "thought experiments" for me. I do not have the benefit of a wind tunnel or smoke tests to prove it. It just seems to make sense, from a fluid dynamic point of view. I guess watching all of those videos of strings taped on a wing did something to me!

I'll be the first to defer to an actual engineer on this. But if you are correct, we need to correct it in the FAA circular, etc. We do not need to stick to our ideas merely because they were taught to us that way.  :) —Preceding unsigned comment added by Graysoc (talk • contribs) 04:39, 27 October 2009 (UTC)

Hi Graysoc. Thanks for your prompt and thoughtful reply. (Which you have done correctly. When leaving a message on a Talk page sign by typing four "tildes" - four little sine waves - on my keyboard the tilde is the key at the top left, next to the number 1. When saving or previewing, the four tildes automatically turn into your name and the date and time.)

I will study your comments and add my own here in the near future. Regards. Dolphin51 (talk) 05:21, 27 October 2009 (UTC)

I have now had a close look at the Pprune site you quoted above. An interesting collaborative effort, but unfortunately based mostly on intuition. Not much evidence of science. Several of the contributors made statements that extending wing flaps increases lift. As you know, that is incorrect. Lift is equal to weight times load factor - whether the flaps are extended or not does not alter that fact. Extending wing flaps doesn't increase lift - it increases the maximum lift coefficient and reduces the stalling speed.

Another common statement on Pprune is that extending flaps reduces the angle of attack and therefore reduces the strength of the trailing vortices. Unfortunately that is also unsound. It is true that when an aircraft slows the AoA must increase, and when it accelerates the AoA must decrease, but the actual value of AoA is arbitrary. It can be measured relative to the line from the trailing edge to the center of the leading edge circle; or it can be measured relative to the underside of the wing; or it can be measured relative to the zero-lift line; or any other line. When flaps are extended the result is a new airfoil shape with a new arbitrary line against which to measure AoA. Whether extending flaps increases or reduces the AoA is arbitrary, depending on how we choose to measure it. So it is not rigorous to say that extending flaps reduces the AoA.

What can be said with certainty is that extending partial-span wing flaps reduces the AoA on that part of the wing outboard of the flap. (That is why extending wing flaps is usually a protection against spinning - it reduces the loading on the outboard section of the wing.) Consequently with flaps extended the vortex from the tip is reduced in strength, but it is replaced by a much stronger vortex from the outboard end of each flap. See the photograph of the 757 on Pprune! Regardless of where the vortices leave the wing, they quickly roll up into two large trailing vortices. See the diagram in AC 90-23F, sub-section 5.

I agree that it would be good to get 90-23 amended so that it either drops the comment about clean and simply says the strongest wake turbulence is heavy and slow; or that it explains why wake turbulence is stronger with a clean wing, given that induced drag is greater with flaps extended. Dolphin51 (talk) 11:50, 27 October 2009 (UTC)

I have studied the thread on Pprune and I now see what was meant by saying extending flaps reduces angle of attack. Furthermore I agree that extending flaps reduces the angle of attack. Several of the commenters on Pprune commented correctly that induced drag is dependent on the square of the lift coefficient. As the flap setting is changed the angle of attack changes significantly but lift coefficient does not change, at least not significantly. (Fowler flaps increase the wing area and that causes a reduction in lift coefficient. However, as soon as the Fowler flaps have been extended the pilot usually reduces airspeed, and the reduction in airspeed causes the lift coefficient to increase to its original value and higher.)

Extending flaps changes angle of attack but doesn't significantly change lift coefficient. Consequently there is no change of lift coefficient to explain a change of induced drag or the strength of trailing vortices.

Induced drag is strongly dependent on aspect ratio and the shape of the spanwise lift distribution. An elliptical spanwise lift distribution is perfect. Extending partial-span flaps severely disrupts the spanwise lift distribution and it is this which explains the increase in induced drag, and the strength of trailing vortices.

I have drafted some thoughts which I intend to post on the Pprune thread in the next day or so. Dolphin51 (talk) 02:31, 29 October 2009 (UTC)

I have now added my thoughts to the above-mentioned thread on Pprune, under the User name "Dolphin51". Dolphin51 (talk) 06:14, 30 October 2009 (UTC)

Thanks for helping

i appreciate your pointing me to the correct method of commenting on an article - I imagine it was obvious to you that I could not figure out the appropriate way to do so! I suspect it'll take me a while to figure out all the etiquette involved in wikipedia'ing! —Preceding unsigned comment added by GanjaManja (talk • contribs) 04:53, 30 October 2009 (UTC)

Impact pressure

The article Impact pressure following your reversion of my edit - grounds noted - leave the misleading statement that impact pressure is synonymous, in the aerodynamic context, with dynamic pressure. I feel it is imperative to distinguish between these terms - see article discussion page where a proposal to establish a redirect to Dynamic Pressure is contested. I have changed the text to reflect that technical literature may present them as synonymous, but that such a position is untenable. See NACA TR 837 (Langley, 1946) - NASA Tech Reports Server Accession ID 93R21204. (Weirpwoer (talk) 04:17, 31 October 2009 (UTC))

Thanks. My understanding of the situation regarding dynamic pressure and impact pressure can be seen by some edits I made recently to Dynamic pressure. See the diffs.

Please looks at my edits to see my understanding of the two, and then let me know what you regard as the difference, and why you say that, in compressible flow, dynamic pressure and impact pressure are not synonymous. I'm happy to accept such a viewpoint providing I can be convinced. Best regards. Dolphin51 (talk) 11:41, 31 October 2009 (UTC)

My apologies for the delay in following up on this matter. I shall put together a PDF for you on the subject as it will require deriving two solutions from Euler's equations - one where rho is held fixed, arriving at the well-known Bernoulli equation, and two where it is allowed to vary isentropically, arriving at the less commonly known Barré de Saint-Venant equation for subsonic compressible flow. I will include for you suitable references in addition, both to a US Hydrographic Office publication (216), a NACA report from the 1940s and a comment by J. D. Anderson in a couple of his notable publications. In the meantime there ought to be a distinction made in the terminology - and the equations to which the terms refer - in the NACA report published by Langley in, I believe, 1949, report number 834. (Weirpwoer (talk) 11:28, 15 November 2009 (UTC))

Thanks. I look forward to your explanation. Dolphin51 (talk) 06:18, 16 November 2009 (UTC)

The NACA Report No. 834 is available here. It mentions the word pressure only twice, both times in the context of static pressure rather than dynamic or impact pressure. Dolphin51 (talk) 00:03, 17 November 2009 (UTC)

The correct report is NACA Technical Report 837, Standard Nomenclature for Airspeeds with Tables and Charts for use in Calculation of Airspeed. (Langley, 1946.) It is typical of most documents on this subject in that it uses dynamic pressure for incompressible flows, and defines it as ${\tfrac {1}{2}}\rho V^{2}$, and uses impact pressure for compressible flows. I have no difficulty with these definitions.

A minority of authors in the field of compressible flows (mostly British authors) use the expression dynamic pressure instead of impact pressure. I have a difficulty with Weirpwoer's position if he is saying that compressible dynamic pressure is not synonymous with impact pressure. Dolphin51 (talk) 05:09, 17 November 2009 (UTC)

My position is that dynamic pressure is defined merely by convention, by holding density along a streamline constant. Impact pressure can be illustrated by the compressible Bernoulli equation, which are solutions to Euler's equation under conditions in which density can vary isentropically. The convention in the American technical literature (above mentioned NACA report on nomenclateur) agrees with this, and is by far the clearest in setting apart these two terms. Dynamic pressure is only a good approimation to impact pressure at Mach numbers sufficiently low enough to assume the flow is incompressible (ie < Mach 0.3, by convention.) The symbol presented on the page on impact pressure, qc, is used in the NACA report specifically to distinguish it from q (the dynamic pressure). (Weirpwoer (talk) 22:15, 24 November 2009 (UTC))

Thanks for that clarification. I can see we are in agreement on the most important things.

We agree that, in incompressible flows:

stagnation pressure – static pressure = ${\tfrac {1}{2}}\rho v^{2}$

and that this quantity is universally known as dynamic pressure, $q$.

We also agree that, in compressible flows:

stagnation pressure – static pressure = ${\tfrac {1}{2}}\,\gamma \,p_{s}\,M^{2}\,$

and that this quantity is symbolised $q_{c}$. The only area for debate is what name should be given to $q_{c}$.

I concede that most authors in the field of compressible flows give $q_{c}$ the name impact pressure. However, I have cited two examples of British authors who call $q_{c}$ compressible dynamic pressure or dynamic pressure. This is just one of many examples of differences in nomenclature on different sides of the Atlantic.

These two authors are not saying that, in compressible flows, the difference between stagnation and static pressure is ${\tfrac {1}{2}}\rho v^{2}$. They are saying, correctly, that the difference between these two pressures is the compressible dynamic pressure:

${\tfrac {1}{2}}\,\gamma \,p_{s}\,M^{2}\,$

These two authors also demonstrate the following interesting relationship:

$q_{c}={\tfrac {1}{2}}\rho v^{2}\left(1+{\tfrac {M^{2}}{4}}+{\tfrac {M^{4}}{40}}+...\right)$

or, alternatively:

$q_{c}=q\left(1+{\tfrac {M^{2}}{4}}+{\tfrac {M^{4}}{40}}+...\right)$

Regards. Dolphin51 (talk) 02:53, 25 November 2009 (UTC)

In your 17th November 2009 posting to the discussion page of impact pressure, you wrote:

"The majority of authors, and certainly NACA Technical Report 837 [Standard Nomenclature for Airspeeds with Tables and Charts for use in Calculation of Airspeed. (Langley, 1946.)] [...], define dynamic pressure as ${\tfrac {1}{2}}\rho v^{2}$. This is the difference between stagnation pressure and static pressure only in incompressible flows, and is usually acceptable in compressible flows up to approximately 0.3 Mach. Impact pressure is the difference between stagnation pressure and static pressure in compressible flows, including compressible flows above 0.3 Mach. Clearly, impact pressure and ${\tfrac {1}{2}}\rho v^{2}$ are not the same."

Without repeating the usual assumptions (i.e. perfect gas, isentropic process, neglecting gravity, etc), this remark frames the distinction in the terms rather well. By convention dynamic pressure is utilised well into the supersonic regime, for reasons I do not myself fully appreciate, although it is understood that the use of dynamic pressure ceases for most practical purposes to yield a good approximation for the difference between stagnation (total) and static (free-stream) pressures, beyond about Mach 0.3. The density variation in a fluid such as air for Mach numbers < about M0.3 is under 5%. By about Mach 0.5 the variation reaches about 12%, and about 20% by Mach 0.7, and at Mach 1.0 is about 35 to 40% (ballpark percentages as I don't have a spreadsheet set up to give exact figures).

The 'incompressible Bernoulli solution' of ${\tfrac {1}{2}}\,\gamma \,p_{s}\,M^{2}\,$ is the same thing as ${\tfrac {1}{2}}\rho v^{2}$ (noting the usual caveats when dealing with thermodynamic relations involved - flow through a sound wave involving no heat addition, effect of friction negligible, hence isentropic flow). If a 'compressible solution' is required, density must be allowed to vary in some way. For an irrotational (sorry, not 100% sure about this bit - for a later discussion), inviscid, perfect gas, neglecting gravity (these assumptions, so far, are also made in deriving a fixed-density 'incompressible Bernoulli solution'), the isentropic relations can be used to derive the so-called Saint-Venant equation for flows at and below Mach 1.0 (indeed, the Saint-Venant equation is accurate to second order to around Mach 1.2). You have even give a binomial expansion for this solution. I will derive it for you over the next couple of days (I'm not familiar with LaTeX). The Saint-Venant equation (not a very widely recognised name for the solution) can be written as:

(SV1) $M^{2}={\frac {2}{\gamma -1}}\left[\left({\frac {p_{0}}{p_{1}}}\right){}^{\frac {\gamma -1}{\gamma }}-1\right]$, or

(SV2) $V^{2}={\frac {2a^{2}}{\gamma -1}}\left[\left({\frac {p_{0}-p_{1}}{p_{1}}}+1\right){}^{\frac {\gamma -1}{\gamma }}-1\right]$

Where: $V$ is true airspeed, $\gamma$ is the ratio of specific heats (having a constant value of 1.4 for a calorically perfect diatomic gas in the flow regimes we're dealing with here), ${p_{0}}$ is the total pressure (stagnation pressure) and ${p_{1}}$ is the static pressure in the free-stream flow. The speed of sound, locally, is given by $a$, and the free-stream Mach number by $M$.

In conclusion, dynamic pressure is good for incompressible flow only (which we recognise as being a mythical scenario but have found it convenient for simplifying equations for flows < M 0.3) and is defined by the solution ${\tfrac {1}{2}}\rho v^{2}$, while impact pressure accounts for the difference in total and free-stream pressures brought about by velocity changes along a streamline, taking density as varying isentropically. (Weirpwoer (talk) 15:09, 25 November 2009 (UTC))

(P.S. - Comment re recent edit of impact pressure page, in sentence on air data computer, noted - delirious moment there! I've corrected the mistake.) —Preceding unsigned comment added by Weirpwoer (talk • contribs) 15:13, 25 November 2009 (UTC)

You are right! I have been mistakenly assuming $q={\tfrac {1}{2}}\,\gamma \,p_{s}\,M^{2}\,$ is valid for all Mach numbers. I now see that it is nothing more than ${\tfrac {1}{2}}\rho v^{2}$ in a compressible fluid, so only valid up to about M0.3. I need to revise my thinking on this part of dynamic pressure. I will get back to it in the next day or two. Thanks for alerting me to my error. Dolphin51 (talk) 21:43, 25 November 2009 (UTC)

FYI

Dan Frederiksen who you greeted so warmly on their talk page happens to be a block dodger. He says Wikipedia is full of "evil" because his nonconstructive edits are constantly being reverted and he'd rather make personal attacks than learn the correct way of doing things. He's been blocked from editing for a week, but has made another account to get around it. I've reported him again, but I figured I'd let you know. Cyberia23 (talk) 22:35, 7 December 2009 (UTC)

Thanks for that information. User:Dan Frederiksen only made fourteen edits before being blocked. Two of the edits were to his or her own Talk page, so that leaves only twelve substantial edits. Seven of the twelve edits were made prior to 15 April 2008, so that leaves only five substantial edits since 15 April 2008. I have examined these five edits very closely and can find nothing offensive. With so little evidence how can Wikipedia be sure Dan Frederiksen is a sockpuppet? Dolphin51 (talk) 09:55, 8 December 2009 (UTC)

I thought the account started a few days ago because your greet message was dated 6 December 2009. I didn't know it was a few years old already. I'll fill you in to what is going on... An anon user 85.83.19.103 popped up on UFO Hunters, the article for a paranormal documentary show which ran for 3 seasons on History Channel and was canceled abruptly by the network before its 3rd season even finished. This sort of started a protest on fan forums supporting the show and even the producers ran an online petition on their website "UFOMagazine.com" to have the show brought back. The petition called for a season 4, but instead, History finished out the last episodes of season 3 in a 4 episode marathon and called an end to it.

Still, the petition for bringing the show back is still ongoing – and has been since July of 2009. I honestly believe it remains simply because UFOMagazine updates their site every 2000 years. It's old news and apparently not getting them anywhere. They are really slow and focus more on getting their rag out instead of updating their online info. I have found an equal amount, if not more protest by viewers against the show than for it, and of course there are those fanatics out there who think it's a government conspiracy or something.

Anyway, the anon editor kept adding a note about the online petition as a separate section stating there was an online petition and the show won't be renewed, yadda yadda... if this person would actually read the article, they would see in the opening statement of the article the show ran for 3 seasons (not 4) and there is already a mention of the petition in the section for Season 3. The petition is not linked to the source because links to petitions are against policy which avoid bias and maintains neutrality. All the anon's edits are simply repeating really what was already there.

Anon user kept constantly adding this info over and over and over - five other edits have undid his edit. I myself undid it twice and at least I tried to explain why on this person's talk page, but I quickly find that he has been round and round with other editors and admins and has numerous warnings for edit warring and personal attacks. I reported the anon for further edit warring, I reported that he called us douchebags and morons for undoing his edits and so he gets a week block for it.

Next day or so I see this Dan Frederiksen person who seems to come out of nowhere and makes the same edits as 85.83.19.103 and "agrees" with them... I'm sorry that's an obvious red flag that it's a sock puppet of the same individual. To confirm, all I had to do was read his conversation with you on his talk page... which by the way tells me this person is strange to say the least ..."I have considerable experience with the darkness of mankind and the weakness of men in the face of it." ... seriously, who talks like that? Plus, I don't know what his deal is with Hu12. He seems to really hate this person for some reason. Just read what he says...

Anyway, I notified Tedder who gave the anon a week block, that Mr. Frederiksen is the same individual and he apparently agreed with me. Sock puppetry is a no no especially when dodging blocks. Mr. Frederiken says were simple minded idiots but if he really thinks he could pull a fast one like that, then he's clearly the idiot. Cyberia23 (talk) 21:14, 8 December 2009 (UTC)

Thanks for your comprehensive explanation. I have replied to the Admin at User talk:Tedder#Blocked user has returned. Dolphin51 (talk) 11:48, 9 December 2009 (UTC)

Dan Frederiksen is very likely his real name. A guy by that name started this thread on a web board for private space enthusiasts (pretty much all the big guys post there: Armadillo Aerospace, Masten Space and a couple more). They've decided to keep him as their pet troll for the amusement value. He is very likely completely sincere (and wrong, of course). Peter Lund 80.63.230.158 (talk) 22:51, 20 December 2009 (UTC)

Thanks Peter. That's interesting. Dolphin51 (talk) 00:22, 21 December 2009 (UTC)

Just made a redirect page. Is it okay and within wiki rules?

I was reading about low earth orbits and typed in "leo vehicle" to wikipedia. I was surprised that nothing came up. Do you agree with the redirect that I created?

Best regards,

Jeremy Jez 006 (talk) 16:30, 24 December 2009 (UTC)

Hi Jeremy. I have checked your handiwork and it is fine. It is within wiki rules. This is one of the good functions of Wikipedia that doesn't exist with a paper encyclopedia. If you looked for Leo vehicle and it didn't lead you straight to the Wiki article, and others are likely to do the same thing, then that indicates a re-direct is warranted. A lot of re-directs are based on alternative spelling of the article name, and sometimes the alternative spelling is not strictly correct, so there aren't any particular rules about what can and cannot be used for a re-direct. Regards, Dolphin51 (talk) 11:15, 25 December 2009 (UTC)

Thanks for the welcome!

Nice to meet welcoming people as well as a fellow engineer!

LogisticsMarmoset1729 (talk) 17:14, 12 January 2010 (UTC)

Hi! I'm pleased you appreciated the welcome. Best regards. Dolphin51 (talk) 11:53, 17 January 2010 (UTC)

Re: Clearway

Glad I could help. --  Denelson83  03:19, 14 January 2010 (UTC)

Thank you for the welcome

What a surprise! Thank you very much for welcoming me. Like you, I am an aeronautical engineer. Ulfmichel (talk) 04:25, 11 February 2010 (UTC)

We need more aeronautical engineers! Cheers. Dolphin51 (talk) 05:20, 11 February 2010 (UTC)

Thanks for Barnstar

It was an interesting experience :-) I felt that, while you 2 differed on this issue, you both made sense and both are committed to WP. Thanks for your own efforts to calming things down. Best wishes, --Philcha (talk) 08:03, 10 March 2010 (UTC)

Acknowledged! Dolphin51 (talk) 08:09, 10 March 2010 (UTC)

Open ended tube oriented perpendicular to a flow to reduce pressure within the tube

Some types of sprayers and carburetors make use of open ended tube oriented pependicular to a stream of air in order to draw out fluid (carburetors also use two stages of venturis, boosters that exit into the venturi section of a carburetor).

As a simple home experiment, you can use a straw, a container of water, and a hair blow dryer to see this effect by water being drawn up the straw some distance due to the lower pressure in the straw. When the air flow is directed perpendicular to the straw, that flow is diverted away from the opening, creating a low pressure zone at the open end of the straw and usually some type of vortice that starts at the leading edge of the straw. With a secured, unbreakable container, ear plugs, and a leaf blower you can make a sprayer, if the distance between water and end of straw is short enough.

Even if the static pressure of the flow is slightly above ambient, there's still a low pressure zone at the open end of the tube. If the open end of the tube is inserted into a spool of thread, creating a crude semi-static port, the effect is much less, and if a true static port is setup (flush mounted to a large enough surface), then the the straw's pressure will essentially be the same as the static pressure of the flow, eliminating the tube in a flow effect.

I've seen some articles that claim this tube setup indicates static pressure, used to show Bernoulli effect of lower pressure in a flow, but you need a static port to do this properly.

What I haven't seen is a name given to this effect, or a description of how this effect works. Again, some sprayers, including some versions of the classic "flit gun" used this crude method of simply exposing the open end of a tube into a pumped flow of air. The effect is known and used in very old sprayers, but I haven't seen any articles describing this effect.

Are you aware of any articles about this? Would this be a good candidate for a new wiki article? I can't even think of what to name it.

You can just copy and paste this along with your response to my talk page if it's OK.

Jeffareid (talk) 10:40, 29 March 2010 (UTC)

You are right about the vortex at the leading edge of the straw. The air pressure in the stream of air flowing out of the sprayer or leaf blower is equal to atmospheric pressure. However, when the end of a tube is placed in this stream of air, a small part of the stream is forced to divert around the edge of the tube. It then resumes its original place in the stream. It diverts around the edge of the tube in a partial vortex. As you know, the pressure at the core of a vortex is very much lower than the surrounding pressure because the speed in the core is very much faster than the speed of the surrounding air. It is the low pressure in the core of this partial vortex that draws water up the straw. I am not aware of any particular name applied to this phenomenon. It illustrates such well-known phenomena as vortex flow and Bernoulli’s principle. Dolphin51 (talk) 22:02, 29 March 2010 (UTC)