Techniques for improving monotonicity in a fourth-order finite-volume algorithm solving shocks and detonations

Abstract

Techniques are proposed to reduce numerical oscillations in a fourth-order, finite-volume algorithm for solving thermally-perfect, reacting fluid flows with strong discontinuities, such as shock or detonation waves. These additional mechanisms have proven necessary for multispecies flows solved at fourth-order accuracy, and contribute towards bounding the variation of the solution in the vicinity of strong discontinuities. There, oscillations can form due to strong gradients in the flow and may be further intensified by numerical procedures introduced to treat the thermally-perfect thermodynamic system and physical constraints on species mass fractions. The new techniques are designed to respect the conservative property of the base algorithm, retain fourth-order accuracy of the solution in regions of smooth flow, and cooperate with the high-order piecewise parabolic method limiter. Extensive numerical tests, ranging from multispecies mixing flows to reacting flows with detonations, are performed to verify that the new techniques meet the design criteria while effectively suppressing oscillations. The proposed techniques are applied to solve the Shu-Osher and double Mach reflection problems and a set of oblique detonation wave problems. The results demonstrate the effectiveness and robustness of the algorithm.