Coupling methodology of 1D finite difference and 3D finite volume CFD codes based on the Method of Characteristics

This paper describes the methodology followed to perform a co-simulation between 1D (OpenWAM) and 3D (FLUENT) CFD codes. The Method of Characteristics (MoC) has been chosen to transfer the information between the two domains by properly updating the boundary condition at the shared interface. A short explanation of the MoC is provided, including the modifications needed by the Riemann invariants when dealing with non-homentropic flow. The implementation of the coupling is explained, focusing on the particular approach required by FLUENT in order to obtain the Riemann invariants. Two validation tests have been performed. The Sod’s problem has been used to test the numerical accuracy of the coupling methodology. On the other hand, an impulse test rig configuration has been simulated to show the potential capability of a co-simulation in terms of reducing the computational cost. In both cases a good agreement in the solution is found.