Talk:Advection

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Merge

I merged Advection with Advection Equation as both the articles are very small and there was a lot of overlap. I think that one pages called advection with an advection equation heading would work fine. If they get two big then separate them but at the moment I cannot really see the point as a description mathematically helps illustrate advection so they go hand-in-hand. Rex the first ^{talk | contribs} 21:43, 14 April 2007 (UTC)[reply]

Sounds good to me. Might be a good way to eliminate the stub status of this article User A1 04:57, 15 April 2007 (UTC)[reply]

I support the merge also, since nothing was lost, and I can't think of any reason for a separate section for advection math. Put it at the end, as here. But many of the variables in the math section are not defined, so somebody needs to work on it. S B H arris 19:01, 18 April 2007 (UTC)[reply]

Advection vs. convection

According to the article Convection, this term "is used to refer to the sum of advective and diffusive transfer". The description in the present article, however, seems to suggest that convection can mean the diffusive component only. Is there any support for this view?

Err, convection certainly includes buoyancy-driven flow so it is most definitely not just the diffusive component. djh 131.111.85.223 (talk) 09:42, 26 February 2010 (UTC)[reply]

Convection is the sum of advection (bulk current transport) and diffusion, so it must have an advective component, or otherwise it would simply be called "diffusion." S B H arris 17:24, 26 February 2010 (UTC)[reply]

In meteorology at least, "convection" is vertical advection (usually where the fluid is neutrally or stably stratified). I updated the "Meteorology" section to reflect this. Whereas advection is transport by fluid motion in any direction, the term "advection" in meteorology usually refers to primarily horizontal (synoptic-scale) motions, and "convection" is reserved for significant vertical motions (usually involving deep clouds).Burgel~enwiki (talk) 20:56, 21 April 2015 (UTC)[reply]

Meaning of advection

I just came here to find the meaning of advection, only to discover that it's not here! The page says a lot of things but assumes that you already know the meaning of the word. Somebody more expert than me should provide a simple but accurate definition. djh 131.111.85.223 (talk) 09:42, 26 February 2010 (UTC)[reply]

The first sentence was okay, but the English was written so that it could be misunderstod. I've nailed it down, rearranged some material in the lede, and clearly differentiated it from convection, which is the sum of advection (bulk current transport of materials in fluids) and diffusion (transport which requires no currents). S B H arris 17:18, 26 February 2010 (UTC)[reply]

I do agree, with the words above. And what striked me, is term, "conservative", in the first line. Is it really so? If it is, then it might destroy singlehandedly other peripheral words attached below it, sure enough, "the thing" is loosely interconnected, not giving enough natural rise to the fact that should come out as evident. This thing must be check for its mathematical foundations. And I am doing this... Wish me luck-- A. Madhur —Preceding unsigned comment added by 117.197.65.114 (talk) 12:20, 6 August 2010 (UTC)[reply]

Meaning of the vector field U

The clarity of the article would be much improved if U were defined and described when it is first introduced.--MuTau (talk) 18:48, 26 February 2011 (UTC) Comparison with the wiki article on PDEs makes it clear now what the problem is. Velocity is first defined as v, and then is changed to u when considering a velocity field. It looks like this error resulted from the merger of text from the PDE article. I have made edits to fix this discrepancy. --MuTau (talk) 20:27, 26 February 2011 (UTC)[reply]

I agree with your comments -- the mathematics section is also very loose on describing exactly when a field is being discussed (which is almost always). In addition, advection works on a scalar field. Concentration, heat, etc. is defined at every point, and advection describes how the scalar field changes (over time and space, see for example http://farside.ph.utexas.edu/teaching/329/lectures/node90.html). Confusing scalars and vectors with their respective fields is surprisingly confusing. I found the Del article to be particularly helpful in disambiguating these. I'll try to clarity these -- please check for accuracy! X14n (talk) 03:13, 20 March 2012 (UTC)[reply]

In "The advection equation", this sentence is ambiguous: "It is a linear operator which acts on vector fields." I'm assuming this refers to del, since $\mathbf {u} \cdot \nabla$ acts on the scalar field of $\psi$ . (To make matters more confusing, del can act on a scalar field or a vector field). I'm changing this sentence to read: " $\mathbf {u} \cdot \nabla$ is a linear operator which acts on the scalar fields of a conserved quantity such as concentration or heat."

Edit -- I don't think this is strictly correct, and its redundant and not very informative, so I'm removing this sentence entirely. X14n (talk) 03:36, 20 March 2012 (UTC)[reply]

The discussion of a here is incredibly confusing -- I've tried to clarify that we're referring to the vector field of the advected quantity rather than the transporting vector field. I've also moved this below the discussion of steady flow (which means du/dt=0??), which is still talking about the scalar flow. I'm not an expert here, so input would be appreciated. X14n (talk) 03:58, 20 March 2012 (UTC)[reply]

urge simpler intro

A good scientist engineer can explain something to his peers; a great one can explain it to the average person. The intro is a little to complicated and jargon laden; I would urge re writing along the lines of the advection vs convection (and eddy diffusion is in itself jargon). Wiki has to satisfy people of wildly different skill sets; thus, the intros of articles like this need to be pitched at a level that is suitable for a very broad audience; technical detail, later on, is fine, but not in the intro. —Preceding unsigned comment added by 108.7.14.40 (talk) 15:09, 26 April 2011 (UTC)[reply]

I'm editing the intro for clarity. I'm finding that it also contains a number of technical inaccuracies. "Meteorological or oceanographic advective transport is perpendicular to isobaric surfaces and is therefore predominantly horizontal" is patently false -- cloud formation, for example, is density-driven vertical advection of moisture.

The "Distinction between advection and convection" section needs some serious work. Again, the "advection is horizontal" is not supported by the cites (the first one has a whole chapter on vertical advection). I can't see how these sentences makes any sense, while the convection article is quite clear: "An example of convection is flow over a hot plate or below a chilled water surface in a lake." and "Another view is that advection occurs with fluid transport of a point, while convection may be considered as fluid transport of a vector." I'm commenting out these later portions as very confusing an in some portion incorrect, but I'm happy to hear clarifications or suggestions. — Preceding unsigned comment added by X14n (talk • contribs) 04:51, 20 March 2012 (UTC)[reply]

illustrations

This article begs for illustrations -- ResearcherQ (talk) 18:44, 25 April 2013 (UTC)[reply]

correctness and clarity of formulas

From the second last formula to the last formula, a factor 1/2 is introduced on the left side. This factor does not appear with the corresponding terms at the right side of the last formula. This seems to be an error - can anybody confirm/disprove ?

The expression Nabla(uu) is not explained clear enough, and Nabla(uux),... does also not seem ultimately clear - a vector field multiplied by a scalar field ? 31.11.9.45 (talk) 22:24, 20 October 2015 (UTC)[reply]

Volcanoes?

Shouldn't there be a mention of volcanoes here? Advection is discussed on the Earth's internal heat budget page. -- Dough34 (talk) 18:51, 29 November 2019 (UTC)[reply]

Distinction between advection and convection

The diagram about the four fundamental modes of heat transfer does not mention evaporative cooling, which is misleading because there are more than four modes.—Anita5192 (talk) 13:37, 19 December 2023 (UTC)[reply]

Correctness of equations and add references

The article says:

In particular, if the flow is steady, then: ${\mathbf {u} }\cdot \nabla \psi =0$

I don't know how you can get that from the fact that the flow is steady, that is: ${\frac {\partial \mathbf {u} }{\partial t}}=0.$

Furthermore, it doesn't seem to get the right solution, as this would imply that for all solenoidal $\mathbf {u}$ , we would have ${\frac {\partial \psi }{\partial t}}=0.$

which is clearly wrong if is $\mathbf {u}$ non-zero.

Could someone correct the equations and add some references? ShirAko1 (talk) 17:22, 15 October 2024 (UTC)[reply]