A thin flat plate is held at an angle of attack in a stream of air at ( ).

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Waves, acoustics and compressible flow · Waves, acoustics and compressible flow

Signal Speeds in Fluids, Ch Oblique shocks, expansion fans and blast waves

Problem

A thin flat plate is held at an angle of attack

\alpha=8^\circ

in a stream of air at

M_1=3

(

\gamma=1.4

). ((a)) By shock-expansion theory, find the pressure ratios

p_{\rm lower}/p_1

and

p_{\rm upper}/p_1

on the two faces. ((b)) Find the lift and drag coefficients

C_L

and

C_D

, using the dynamic pressure

q_1=\tfrac12\gamma p_1M_1^2

. ((c)) Compare with the linear results

C_L=4\alpha/\sqrt{M_1^2-1}

and

C_D=4\alpha^2/\sqrt{M_1^2-1}

, and say why the agreement is not as close as for the plate at

M_1=2

\alpha=5^\circ

in the text.

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