Linked Questions

246
votes
14answers
69k views

What really allows airplanes to fly?

What aerodynamic effects actually contribute to producing the lift on an airplane? I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
8
votes
1answer
8k views

What is a Physically Accurate Explanation for the Kutta Condition?

Countless arguments between highly intelligent people have been waged (on this very site in fact) as to exactly how lift can be explained in an experimentally and mathematically rigorous way. Taking ...
5
votes
2answers
2k views

Does a conductor of total charge zero placed in a uniform external electric field experience net force?

The question I have in mind is: If we place a conductor (arbitrary shape) of total charge zero in a uniform external electric field $\textbf{E}_0$, does it experience any net force? Why (not)? Now I ...
5
votes
3answers
525 views

What is the theoretical justification for a fluid flow's being irrotational?

I am not a fluid dynamicist, and I really just began thinking about this problem as my curiousity drew me into building an answer for the question What really allows airplanes to fly?. It is very ...
5
votes
3answers
4k views

When is a flow vortex free?

To solve problems in fluid dynamics one states often the assumption that the flow is vortex free i.e. $rot(u) = 0$ It is a basic assumption which is needed for potential flow problems etc.. My ...
5
votes
1answer
811 views

Conditions of applicability of potential flow about an airfoil

In many cases the flow about an airfoil is calculated by solving the Laplace equation, (for example in the Hess-Smith panel method). If the velocity field is irrotational and its divergence its zero, ...
1
vote
2answers
904 views

By what mechanism is lift produced on a rotating cylinder in an inviscid flow?

I am taking some introductory fluid dynamic classes, and have become very confused by the Kutta-Joukowski theorem. One of the conclusions that can be derived by applying Kutta-Joukowski is that a ...
2
votes
3answers
303 views

Fluid Flow and Reynold's number

I am confused about the conditions on the Reynolds number for an ideal fluid flow. Now, an ideal fluid flow is approximated by real fluid flow with a high Reynolds number (except for if the flow ...
1
vote
3answers
397 views

Equal transit time fallacy and Newton's laws of motion

I've seen the equal transit time theory being used to explain aerodynamic lift [basis is Bernoulli's principle] several times. However recently I've been told that there is NO physical compulsion for ...
3
votes
2answers
70 views

What is irrotational flow? How to judge?

For example, when the wing moves horizontally, the direction of fluid flow changes first to upward at the leading edge of the wing and then to downward at the trailing edge. Does it rotate? If the ...
1
vote
0answers
57 views

How does Bernoulli's principle produce wing lift? [duplicate]

In the Ray Kurzweil's book How to create a mind is said that: The mathematics of how Bernoulli's principle produces wing lift is still not yet fully settled among scientist [...] What does this ...
-3
votes
1answer
60 views

If the wing is absolutely smooth and has no friction, will it still generate lift?

I think it will generate lift, because downwash air flow still exists. But I'm not sure if I'm right.
0
votes
1answer
77 views

Lifting line trailing vortex/vortex sheet inside flow field

With refference to the lifting line model, do we consider trailing votex or vortex sheet to be inside the flow field ? because the vortex core is rotational and we violate one of the flow field ...