Preliminary Studies on Continuously Varying Mach Number Tunnel

In this paper, shock-shock interactions are investigated experimentally, in a varying Mach number flow. The tunnel was operated in accelerating and decelerating modes, with average dM/dt of 1.67. The shock angles were used to obtain the Mach number upstream from the steady gas dynamics expressions, and compared with pressure ratio based Mach number at the exit. It was found that the Mach numbers thus obtained matched well, within the error bars, for both accelerating and decelerating cases. This suggests that the dM/dt of 1.67 is not sufficient to invoke unsteady gas dynamics behavior. This was also corroborated by straight line shockwaves.