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Section
10: Potential Flow, Lift, and Drag |
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10.1 |
The
occurence of irrotational (potential) flows. The definition of the velocity
potential f. |
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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"). |
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10.3 |
The
equation for the pressure distribution (Bernoulli's integral in terms of
f. |
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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. |
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10.5 |
[Two-dimensional
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.] |
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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 (Kutta-Joukowsky theorem), and (c)
the indeterminacy of the circulation in 2D potential flow theory. |
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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. |
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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. |
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10.9 |
Qualitative
picture of the 3D flow field over a finite lifting surface (wing). Wing-tip
vorticies, downwash, etc. Induced drag. |
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10.10 |
Overview
of lift and drag forces on lifting surfaces. |
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Reading
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Fay, Chapter
11, or, for example, Potter & Foss, pp 360-390, 454-468 |
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