Talk:Potential flow

message: This article is a bit confusing to me... and I'm an Aeronautical Engineer. The material presented is a highly mathematical approach, which is hard to understand for most non-mathematicians. I'l have a go at re-writing it when I have time. If anyone else is thinking of re-writing it, it'd help to include an example or two, mention actual uses (lifting cylinders, Joukouski transforms)...
(Halabut 23:40, 9 November 2005 (UTC)
thread_title: Confusing article

message: Potential flow does not have to be inviscid. I am removing these references.
The existing external link confirms this.
Josh Quinnell 02:47, 2 December 2005 (UTC)
thread_title: Inviscid condition

message: I suggest this article to be merged with the article on popential flow, since pretty much all the content of this article is already covered there and the rest would well fit in. —Preceding unsigned comment added by 128.196.169.66 (talk • contribs) 07:15, 31 January 2008
:The above was copied from Talk:Potential flow in two dimensions. — Crowsnest (talk) 19:15, 23 April 2008 (UTC)
replies: text: Since there were no objections, the merge has been performed. Crowsnest (talk) 22:47, 27 June 2008 (UTC)
thread_title:  Merger proposal 

message: they're a real mess.  need consistently sized equations.  why oh why the wikipedia web designers did not set one size for the equations (as done in every textbook i've seen, where they're the same height as the bodytext) escapes me...  —Preceding unsigned comment added by 141.213.220.186 (talk) 07:00, 24 April 2008 (UTC)
replies: text: The equations should be larger than the body text, but consistent in themselves.  Unfamiliar characters and vector symbols would be lost in the same size font. TheBobGeezer (talk) 14:07, 15 March 2022 (UTC)
thread_title:  Equations 

message: I'm not sure if this article is the best place for it, but it's worth mentioning one topological tweak needed to potential flow that is especially necessary for analyzing lift in airfoils. In particular, the lead article figure "Streamlines around a NACA 0012 airfoil at moderate angle of attack" illustrates a case that exactly involves this tweak.
Basically, a pure connected potential flow function has no global circulation and therefore by the Kutta–Joukowski theorem has exactly zero lift, regardless of angle-of-attack. And yet, potential flow is often used to analyze airfoils, where there is global circulation and lift. This sounds paradoxical but there is an important fact: even though the flow locally everywhere may be irrotational and well-defined, the fact that the domain is topologically punctured means there is a free parameter describing how the domain connects. This is nicely illustated in Understanding Aerodynamics: Arguing from the Real Physics, pages 262-263. In general the free parameter is nonzero in which case the potential flow function needs a branch cut, whose location is arbitrary. This gives an overall circulation to the flow but the "source" of circulation is topologically embedded in the airfoil, outside of the velocity field.
In other words, even though all irrotational flows are indeed potential flows, the representing potential function will in general need a branch cut for every puncture, in case of a domain which is not simply connected.
--Nanite (talk) 03:08, 29 May 2020 (UTC)
replies: text: The article Kutta condition explains that a body with a sharp edge establishes a circulation in the flow around itself. This circulation explains the lift on the body. In contrast, a body with no sharp edge, such as a Rankine body, is assumed to establish no circulation about itself and so the body experiences zero lift. Do these observations help illustrate the point you are making? Dolphin (t) 14:09, 30 May 2020 (UTC)
thread_title:  Kutta condition and branch cuts