1. Control of Entropy Generation due to Shock
P M V Subbarao
Professor
Mechanical Engineering Department
Tame the Normal Shock to Reduce Irreversibility !!!

2. Measure of Loss due to Shock
Before the shock:
After the shock:
Across the shock:

3. Mach Number Vs Total Pressure : Normal Shock

4. Mach Number Vs Entropy Generation : Normal Shock

5. Inlets for Supersonic Vehicles

6. Oblique Shock Wave
• When generating object is smaller than a “bluff body”, shockwave can be weaker than NS but stronger than the Mach wave.
This is called as Oblique shock wave
• q -- turning angle or
“wedge angle”
b -- shock angle

7. Flow Through A Supersonic Ramjet (Missile)
What about another Thought Experiment ???

8. Geometrical Description of An Oblique Shock Wavewx b ux
b-q wx u y
b-q q

9. Oblique Shock Wave as a Control Volume
Tangential Normal
Ahead wx, Mtx ux, Mnx
Of Shock
Behind wy, Mty uy, Mny
Shock x y
uy & Mny
wx & Mtx
ux & Mnx
wy & Mty
Vy & My
Vx & Mx
• Shock is A CV & Must satisfy
i) continuity
ii) momentum
iii) energy

10. Continuity Equation for Oblique Shock Wavewx ux Vx wy uy Vy x y
• For Steady Flow thru an Oblique Shock

11. Momentum Equation for Oblique Shock Wavewx ux Vx wy uy Vy x y
Momentum Equation for Oblique Shock Wave
• For Steady Flow w/o Body Forces ( ) - r x u w A + y =
• Tangential Component