The Riemann problem for a drift-flux model of compressible two-phase flow in a variable cross-section duct

Abstract

The Riemann problem for isentropic drift-flux model of compressible two-phase flow in a variable cross-section duct is considered. First, the two-phase duct flow model is established based on the balance laws. Then, by averaging the equations of single phase flow, the drift-flux model in a variable cross-section duct is deduced. The model includes two parts: mass conservation and momentum conservation. The elementary waves that make up the Riemann solutions are analyzed subsequently. Besides, the global entropy condition is imposed to select the physical relevant solution when across the stationary wave. Furthermore, we discuss the uniqueness of Riemann solutions and conclude that the solutions are unique in an expanding duct while not unique in a contracting duct. The results may contribute to the design of numerical schemes in the future study.