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Basics of Fluid Mechanics, 2014a

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12.2. OBLIQUE SHOCK 503<br />

Fig. -12.9. Color-schlieren image <strong>of</strong> a two dimensional flow over a wedge. The total deflection<br />

angel (two sides) is 20 ◦ and upper and lower Mach angel are ∼ 28 ◦ and ∼ 30 ◦ , respectively.<br />

The image show the end–effects as it has thick (not sharp transition) compare to shock over<br />

a cone. The image was taken by Dr. Gary Settles at Gas Dynamics laboratory, Penn State<br />

University.<br />

M 1 M x M ys M yw θ s θ w δ<br />

P 0y<br />

P 0x<br />

2.6810 2.3218 0 2.24 0 30 10 0.97172<br />

The actual Mach number after the shock is then<br />

M 2n<br />

M 2 =<br />

sin (θ − δ) = 0.76617<br />

sin(30 − 10) =0.839<br />

The flow after the shock is subsonic flow.<br />

Part (2)<br />

For the lower part shock angle <strong>of</strong> ∼ 28 ◦ the results are<br />

M 1 M x M ys M yw θ s θ w δ<br />

P 0y<br />

P 0x<br />

2.9168 2.5754 0 2.437 0 28 10 0.96549<br />

From the last table, it is clear that Mach number is between the two values <strong>of</strong> 2.9168<br />

and 2.6810 and the pressure ratio is between 0.96549 and 0.97172. One <strong>of</strong> procedure to<br />

calculate the attack angle is such that pressure has to match by “guessing” the Mach<br />

number between the extreme values.

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