







Section
10: Potential Flow, Lift, and Drag 



10.1 
The
occurence of irrotational (potential) flows. The definition of the velocity
potential f. 

10.2 
Incompressible
potential flows as solutions of Laplace's equation for the velocity potential
with ∂f/∂n specified at
the boundaries (the "Neumann problem"). 

10.3 
The
equation for the pressure distribution (Bernoulli's integral in terms of
f. 

10.4 
An
example: The solution for 2D potential flow over a cylinder. Comparision
with experimental data at high Reynolds number, where the flow might be
expected to be reasonably "inviscid." Discussion of the pitfalls
of potential flow theory. 

10.5 
[Twodimensional
potential flows. Analytic solutions for simple 2D flows: parallel uniform
flow, line source or sink, line vortex. Superposition of simple elemental
flows as representations of flows over 2D bodies.] 

10.6 
Three
properties of ideal potential flows around 2D bodies in an infinite stream:
(a) The nonexistence of drag (D'Alembert's paradox), (b) the relation between
lift and circulation around the body (KuttaJoukowsky theorem), and (c)
the indeterminacy of the circulation in 2D potential flow theory. 

10.7 
The
Kutta condition: an ad hoc criterion, derived from experimental observation,
that allows potential flow analysis to be used to establish the circulation
(i.e. lift) for a 2D shape with a sharp trailing edge. 

10.8 
Comments
on the fact that viscosity, no matter how "small" it may be in
a high Reynolds number flow, is responsible by casing separation for the
existence of both lift and drag. 

10.9 
Qualitative
picture of the 3D flow field over a finite lifting surface (wing). Wingtip
vorticies, downwash, etc. Induced drag. 

10.10 
Overview
of lift and drag forces on lifting surfaces. 

Reading


Fay, Chapter
11, or, for example, Potter & Foss, pp 360390, 454468 






