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Basics of Fluid Mechanics, 2014a

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12.2. OBLIQUE SHOCK 517<br />

The pressure ratios <strong>of</strong> the oblique shock with normal shock is the total shock in the<br />

second case.<br />

P 1<br />

= P 1 P 2<br />

=2.6375 × 10.374 ∼ 27.36<br />

P 3 P 2 P 3<br />

T 1<br />

= T 1 T 2<br />

=2.5141 × 2.6858 ∼ 6.75<br />

T 3 T 2 T 3<br />

Note the static pressure raised is less than the combination shocks as compared to the<br />

normal shock but the total pressure has the opposite result.<br />

End Solution<br />

Example 12.14:<br />

A flow in a tunnel ends up with two deflection<br />

angles from both sides (see the<br />

following Figure 12.14). For upstream<br />

Mach number <strong>of</strong> 5 and deflection angle<br />

<strong>of</strong> 12 ◦ and 15 ◦ , calculate the pressure<br />

at zones 3 and 4 based on the assumption<br />

that the slip plane is half <strong>of</strong> the<br />

difference between the two deflection<br />

angles. Based on these calculations,<br />

explain whether the slip angle is larger<br />

or smaller than the difference <strong>of</strong> the<br />

deflection angle.<br />

δ 2<br />

θ 2<br />

θ<br />

C<br />

stream line<br />

D<br />

1<br />

4<br />

slip plane<br />

B<br />

0<br />

3 φ<br />

2 F<br />

stream line<br />

A δ 1<br />

1<br />

Fig. -12.18. Illustration for Example (12.14).<br />

Solution<br />

The first two zones immediately after are computed using the same techniques that<br />

were developed and discussed earlier.<br />

For the first direction <strong>of</strong> 15 ◦ and Mach number =5.<br />

M x M ys M yw θ s θ w δ<br />

P 0y<br />

P 0x<br />

5.0000 0.43914 3.5040 86.0739 24.3217 15.0000 0.69317<br />

And the additional conditions are<br />

M x M yw θ w δ<br />

P y<br />

P x<br />

T y<br />

T x<br />

P 0y<br />

P 0x<br />

5.0000 3.5040 24.3217 15.0000 1.9791 1.9238 0.69317<br />

For the second direction <strong>of</strong> 12 ◦ and Mach number =5.

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