Investigation of shock attenuation in a shock tube using DSMC method

Shock waves propagating in shock tubes or small channels will be constantly attenuated during propagation due to viscous effect and wall heat conduction. The physical mechanism of this attenuation process has not been clearly discussed in the literature although many investigations have studied the laws and extent of shock wave attenuation under various initial conditions. In this work, the DSMC method is employed to study the propagation and attenuation of shock waves in a 2D planar tube. Numerical results show that the thickness of the unsteady velocity boundary layer in the shock coordinate increases nearly proportional to the square root of time whereas the disturbance of wall effects propagates approximately with the sound velocity behind the shock wave. Appreciable shock curvature is clearly seen in the shock wave and boundary layer interaction corner, which is found to be oscillated. Further analysis shows that the oscillation characteristic of the shock profile is caused by the periodic propagation of low-pressure disturbance generated from the wall surface. Finally, shock wave is found to be more severely attenuated in narrower tube or having larger Mach number at the same time moments.