Troels Dyhr Pedersen.indd - Solid Mechanics
Troels Dyhr Pedersen.indd - Solid Mechanics
Troels Dyhr Pedersen.indd - Solid Mechanics
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
- 62 - -<br />
positive in the x- direction. As the gas follows the shock wave this keeps the pressure and<br />
density high after the shock.<br />
-u2<br />
After<br />
shock<br />
ρ , p , h<br />
2<br />
2<br />
u 1 -u 2<br />
Stationary wave reference<br />
2<br />
0 - u1<br />
u 1<br />
Stationary gas reference<br />
x<br />
Shock<br />
or<br />
detonation<br />
wave<br />
Shock front<br />
Figure 24: The reference frames for velocities in shock waves<br />
Before<br />
shock<br />
ρ , p , h<br />
A sketch of the pressure and temperature distribution in a shock wave is given in figure<br />
25. The pressure rise at the front of the wave is very discontinuous, whereas the following<br />
expansion is continuous as an acoustic wave. In the figure the pressure decreases back to<br />
its original value since there is no chemical heating of the gas. In a detonation wave, the<br />
reactions behind the wave will however increase the pressure and temperature behind the<br />
wave.<br />
P, T, <br />
P 2, T 2, 2<br />
1<br />
1<br />
0<br />
P1, T1, 1<br />
Figure 25: Pressure in a shock wave<br />
Density, pressure and enthalpy are given before the shock and may be determined after<br />
the shock. In the following, density and specific volume are used as appropriate to get the<br />
simplest expressions.<br />
1<br />
x
Change language