We examine the interaction of shock waves by studying solutions of the twodimensional Euler equations about a point. The problem is reduced to linear form by considering local solutions that are constant along each ray and thereby exhibit no length scale at the intersection point. Closed-form solutions are obtained in a unified manner for standard gasdynamics problems including oblique shock waves, PrandtlMeyer flow and Mach reflection. These canonical gas dynamical problems are shown to reduce to a series of geometrical transformations involving anisotropic coordinate stretching and rotation operations. An entropy condition and a requirement for geometric regularity of the intersection of the incident waves are used to eliminate spurious solutions. Consideration of the downstream boundary conditions leads to a formal determination of the allowable downstream matching criteria. By retaining the time-dependent terms, an approach is suggested for future investigation of the open problem of the stability of shock wave interactions.
IntroductionRiemann problems in two spatial dimensions are germane to many problems in experimental, analytical and computational gasdynamics. Familiar examples include the interaction of oblique shock waves in steady supersonic flow, the self-similar problem of transition to Mach reflection from a wedge and the treatment of discontinuous shock fronts in numerical shock fitting algorithms.The well-known approach to the interaction of shock waves has its basis in the work of Rankine (1870) and Hugoniot (1889) regarding the propagation of shock waves. The solution for oblique shock waves was then obtained by Meyer (1908) through a Galilean transformation that imposed a velocity component parallel to the shock front. Also due to Meyer is the development of the Prandtl-Meyer function for expansion through an expansion fan. The development of the theory of shock wave interactions by Courant, Friedrichs, von Neumann and independently by Weise is described by Courant & Friedrichs (1948). By hypothesizing the existence of a vortex sheet at the intersection point, solutions for several interacting shock waves and/or expansion fans may be constructed that are consistent with the experimental observations. A similar approach has been developed for shock-shear layer interactions. The interaction solutions are represented graphically by the intersection in the pressure-flow deflection angle, p-δ, plane of the loci of possible downstream states for the interacting waves. Because of the nonlinear interaction of the waves, problems of non-uniqueness