THE RIEMANN PROBLEM FOR FLUID FLOWS IN A NOZZLE WITH DISCONTINUOUS CROSS-SECTION

Abstract

The system of balance laws describing a compressible fluid flow in a nozzle forms a non-strictly hyperbolic system of partial differential equations which, also, is not fully conservative due to the effect of the geometry. First, we investigate the general properties of the system and determine all possible wave combinations. Second, we construct analytically the solutions of the Riemann problem for any values of the left-and right-hand states. For certain values we obtain up to three solutions whose structure is carefully described here. In some range of Riemann data, no solution exists. When three solutions are available, then exactly one of them contains two stationary waves which are superimposed in the physical space. We include also numerical plots of these solutions.