Development and validation of a Riemann solver in OpenFOAM® for non-ideal compressible fluid dynamics

Recently, there is an increased interest in supercritical CO2 and organic Rankine cycles (ORC) for their ability to achieve higher thermodynamic efficiency. However, the non-ideal gas thermodynamic in these cycles may affect the flow properties critically, necessitating the research of non-ideal compressible fluid dynamics (NICFD). Thus, simulation tools that can accurately predict fluid flows with NICFD are significant. This study presents a new approximation Riemann solver in OpenFOAM for NICFD. The new solver uses a real-gas (look-up table based) approximate Riemann flux calculator (modified from HLLC ALE flux calculator) through adding a new thermodynamic library tightly coupled with the OpenFOAM (R). To validate the solver, three cases are presented, including a NASA transonic nozzle operating with air, to confirm the ability to correctly simulate the transonic flow phenomena and the shock waves; the VKI 2D cascade operated with MDM to assess the ability in simulating non-ideal gas flows typically to industrial applications; and the dense gas flow (MD4M) passing a backward ramp to illustrate the ability of the flux calculator and look-up table mechanism that can work well in the non-ideal region of fluid properties. This study can benefit future engineering applications of computational fluid mechanics of NICFD and the OpenFOAM community.