Experimental generation of spherical converging shock waves

Spherical converging shock waves with incoming Mach number 1.18 are generated in a conical test chamber fitted to a conventional square-section shock tube. A wave cutter is employed to ensure a proper shock transition from the square to a cylindrical straight pipe installed upstream of the convergent section. The incident planar wave is transformed into a spherical shock by the use of an ellipsoidal membrane acting as a gas lens separating two gases with different densities. The transmitted shock wave propagates within the conical section, and accelerates towards the apex. The trajectory and the shape of the shock wave are both characterized by planar Mie scattering. The spherical shock follows the similarity solution proposed by Guderley (1942), whose trajectory agrees very well with the numerical simulation of the Chester-Chisnell-Whitham (CCW) theory for the geometry considered. The procedure demonstrated here provides a potential method for future investigations of shock focusing and Richtmyer–Meshkov instability in spherical geometry.