Mach reflection of detonation wave on porous wall

Abstract

This study reports the Mach reflection of gaseous detonation on porous wedges experimentally, in which the porous wall is consisted of equidistant inline square columns. The smoked foil technique was utilized to monitor the evolution of the triple-point trajectory and detonation cells in the Mach stem region. In addition to the wedge angle and initial pressure of gaseous mixture, this paper also focuses on the effect of porosity and pore size on the Mach reflection and its mechanism. The results show that the strength of the Mach stem is significantly weakened by the porous media compared with that on the smooth wedge, which is ascribed to the diffraction and reflection waves generated by the interaction of the Mach stem front with the pore. Furthermore, the onset of the triple-point trajectory is delayed, the angle of which is decreased. The porosity and pore size present distinct influence on the Mach stem height. With the increase in the porosity and the decrease in the pore size, the Mach stem region is attenuated more dramatically and the Mach stem is harder to be formed or even could not be observed. Furthermore, the triple-point trajectory on the porous wall exhibits local self-similarity and satisfies the frozen limit in the near field and the equilibrium limit in the far field. However, the lengths of the existence of the frozen limit and the transition to the equilibrium limit on the porous wall are found to be much shorter than the hydrodynamic thickness, and the recovery of the self-similarity depends largely on the porosity and pore size.