Talk:Static pressure

Talk Page Archive

Archive 1 has been created with a link at above right. It is an exact copy of the talk page as it was before this edit. Archive 2, when needed in the future, should be a new subpage (same as creating an article) titled "Talk:Static pressure/Archive 2" and the link added to the template on this page's code. For further information on archiving see Wikipedia:How to archive a talk page. See also User:5Q5 for the used archiving procedure. Thank you. Crowsnest (talk) 21:34, 20 May 2008 (UTC)

Incidental advertising

On 20 April Wiki-editor Djhnsn added links to the following two sites:

• Measurement of Static Pressure on Aircraft
• NASA's Measurement of Aircraft Speed and Altitude

On 22 April Wiki-editor Giuliopp removed the two links, commenting that a “sneaky advertisement” was being removed.

These sites contain valuable and relevant reports produced by the US National Aeronautics and Space Administration. However, these web-sites are operated by a commercial organisation (SpaceAge Control, Inc.) and each of the two web-sites contains one page of promotional material supporting the commercial organisation.

The above actions raise the question of how much advertising is tolerable at a site linked to Wikipedia? Wiki advice given here says:

If the link is to a relevant and informative site that should otherwise be included, please consider mentioning it on the talk page and let neutral and independent Wikipedia editors decide whether to add it. This is in line with the conflict of interest guidelines.

In the spirit of this advice, I am mentioning this matter on this Talk page. I believe these two NASA reports are highly valuable and relevant to the concept of static pressure. The reports were written when William Gracey was head of NASA’s Langley Research Center. Gracey subsequently incorporated this material in his book, and that book is quoted and cited in Static pressure. The reports are therefore particularly relevant because they give all Wiki readers access to information that was previously only accessible to those few readers who have access to Gracey's book. I also believe that one page of corporate promotional material is well within the bounds of what can be tolerated. What do other Wiki-editors think? If there is no suitably-substantiated objection to restoring these two links within a week or so I will be inclined to restore them.

If there is a rule that might prevent these two valuable NASA reports from being accessible via Wikipedia I consider that Wikipedia:Ignore all rules is relevant – “If a rule prevents you from improving or maintaining Wikipedia, ignore it.” It is true that each of the links to the two NASA reports contains a page of corporate promotional material but, on balance, I believe these two links improved Wikipedia (until they were deleted.) Dolphin51 (talk) 12:30, 22 April 2008 (UTC)

I find it a bit naive to think that the advertising in question was 'incidental'. User Djhnsn has clearly a much bigger interest in promoting SpaceAge Control Inc. than he has in improving Wikipedia, given that all of his twelve contributions have consisted simply in disseminating links to that company, even if they contain also some relevant information.

I question the authoritativeness of a commercial website that offers to download US governmental documents – even altered with the insertion of advertising pages – in exchange for user's registration, also claiming that such documents have a market value, when they are in fact publicly available, free of charge.

If Djhnsn – who didn't post any explanation on the talk page, as required by WP guidelines – had cared about improving this article, he would have added links to the original documents: 1, 2, which can be located in just a few minutes using Google or the NTRS search engine. There's no question in my mind that these mean attempts to exploit WP for commercial gain should be deleted without hesitation. Giuliopp (talk) 23:16, 22 April 2008 (UTC)

Well, his motives don't matter. But if the direct gov links have all the info and present it clearly, then I'd go ahead and delete the commercial ones. Voice-of-All 01:05, 23 April 2008 (UTC)

Static pressure in HVAC systems?

This article does not appear to at all address the common use of static pressure in HVAC systems. That seems strange, since I think it probably the most common usage. (E.g. a fan might produce 140 CFM of air blowing into a static pressure of 0 in h20, but only 110 CFM blowing into 0.5 in h20.)

I think that's part of what the first archived comment is about, as well... jhawkinson (talk) 18:04, 14 March 2009 (UTC)

Definition

It seems from my perspective you guys are going about this from completely the wrong standpoint. The article keeps making the statement comparing static pressure to Bernoulli's equation. This is not the origination of static pressure in any sense of the meaning. Approaching it from a energy conservation standpoint, all energy and momentum concerns should keep in mind that fluids have macro and micro properties. While dynamics pressure is a macro energy, the pressure term in bernoulli's equation measures the microscopic energy associated with the fluid. This makes more sense viewing the equation as such: P*dV + 1/2*m*v^2=total energy. Now I'm also going to give a derivation from statistical thermodynamics. Static pressure is most easy to conceptualize in that it is the pressure you would measure the fluid having while moving in the same inertial reference frame as the local fluid. From a control volume analysis within the reference frame of the fluid, the pressure times the velocity can actually be found to be 1/3 of the kinetic energy of the gas, directly relating it the density and temperature of the gas. Keep in mind that static temperature is entirely a measure of the kinetic energy of the molecules as observed from the reference frame of the fluid. My point in all this is to say that the static pressure of a fluid is much more than the article seems to be making it out to be. It is a direct measure of the force the fluid applies to its surroundings (whether that is other fluid or a surface). This defines all aerodynamics through Mach=5. It is equivalent to the temperature of the fluid and kinetic energy associated with the microscopic affects of the fluid. So yes, Bernoulli's usage of P_static is entirely 100% factual given the incompressible assumption and it is much more than simply something measured from some reference point in the fluid, as the article states. If anyone wishes to debate this, let me know. Iron_Engineer (talk) 19:54, 1 July 2009 (UTC)

Hi Iron Engineer. Thanks for your comments, and your invitation to debate the subject. Most of what is presently in Static pressure was written by me, and I am keen to remain involved in any improvements and developments of the article.

WP:Verifiability says The threshhold for inclusion in Wikipedia is verifiability, not truth. Consequently, what is important is not what we believe to be true, but what we can verify by posting suitable references and in-line citations. The material presently in Static pressure is fairly well covered by references and in-line citations, so when you write that the article is presently written from the wrong standpoint it doesn't sit comfortably with WP:Verifiability. What references do you propose to use to substantiate any additions you make to present the view of static pressure that you have described above?

I disagree that the article compares static pressure with Bernoulli's equation. The article presents static pressure, dynamic pressure and total pressure as three of the terms in the simplified form of Bernoulli's equation.

You have written that static pressure is the pressure you would measure while moving in the same inertial reference frame as the local fluid. In the case of an aircraft in flight, the fluid is the atmosphere and it is stationary relative to the Earth's surface. Would you say it is possible, or impossible, to have a system in the aircraft to measure static pressure? (The aircraft is moving at speed relative to the reference frame attached to the atmosphere.)

I look forward to discussing this further with you. I'm sure we both have the objective of making Static pressure as good an article as possible. Regards. Dolphin51 (talk) 07:30, 2 July 2009 (UTC)

I have not made any argument concerning a static pressure's measurability. It has long been known that a pitot tube oriented orthogonal to a fluid's motion will measure the static pressure at that point. My entire point rests that static pressure is so much more than Bernoulli's equation. The concept of static pressure has its roots in statistical thermodynamics and its application to Bernoulli's equation flows out of this. My statement about the reference frame of the fluid arises from this. The equations relating static pressure to temperature, kinetic energy of particles, and the interaction it has on the macro scale (ie aerodynamics) can all be directly derived from an atomic level control volume analysis in the reference plane of the fluid.

After rereading the article, I believe my prior wording was a bit harsh. It is a pretty well written article, I just view it as half-complete. From my perspective, this article gives many applications of static pressure without including a through definition of what it actually is and where it comes from. Since static pressure is inherently a measure of atomic level interactions, this can only be achieved by the inclusion of such a description.

Iron_Engineer (talk) 18:37, 2 July 2009 (UTC)

Hi IE. Thanks for your prompt reply. You have written It has long been known that a pitot tube oriented orthogonal to a fluid's motion will measure the static pressure at that point. No. A pitot tube orthogonal to a fluid's motion measures pitot pressure, also known as stagnation pressure, ram pressure or total pressure.

I can accept that you were introduced to static pressure via statistical thermodynamics. I doubt you can verify that statistical thermodynamics is the origin of the term, and that all other applications are less than correct. I was introduced to static pressure via fluid dynamics and aircraft design. (All aircraft have at least one static port. It is a simple hole in the surface of an aircraft's fuselage, and the hole is connected by conduits to the altimeter and airspeed indicator.)

I agree that many things can be written about static pressure, all of it correct. But that doesn't mean all these things have to be in the first sentence of the introductory paragraph. WP:MTAA instructs that technical articles should be accessible to as wide an audience as possible. The article should begin with a simple introduction that is widely accessible to all readers, including children. Later in the article is the place for the PhD candidates to add their information about more complex notions.

Let's keep the discussion going. The objective is to make this article as good as possible. Dolphin51 (talk) 02:52, 3 July 2009 (UTC)

Now we're just talking semantics regarding the pitot tube. If a flow is moving to the right and the pitot tube is oriented pointing upwards at a wall (orthogonal to the flow), it measures static pressure. I'm confident we both know the basic fluid mechanics surrounding pitot tubes and static pressure and I'm of the opinion any thought otherwise is arising from simple miscommunication (what you say is orthogonal I would have called in line or parallel with the flow).

I was never implying altering the lead paragraph. I completely agree this fundamental description I would like to create is of a overly technical information for lead paragraph of something that is used in so many various disciplines and areas of interest. It is just my opinion that giving the fundamentalist description of this fluid property somewhere in the article is essential for a completely thorough encyclopedia article. This like you say would be primarily aimed at people who have studied gas dynamics, a genre that I suspect most people who have not entered graduate school for engineering or physics would not have encountered. Like I said before, I really do like the tone of the article as is and have no intention of changing what is there, I simply envision creating a new section detailing a more rigorous description from a fundamentalist standpoint. An example of what I mean can be found in the article temperature under theoretical foundation.128.6.73.200 (talk) 18:22, 3 July 2009 (UTC)