High-Fidelity Direct Numerical Simulation of Supercritical Channel Flow Using Discontinuous Galerkin Spectral Element Method

Supercritical fluids are suggested as one of the potential candidates for the next generation nuclear reactor by Generation IV nuclear forum to improve the thermal efficiency. But, supercritical fluids suffer from the deteriorated heat transfer under certain conditions. This deteriorated heat transfer phenomenon is a result of a peculiar attenuation of turbulence within the flow. This peculiarity is difficult to predict by conventional turbulence modeling. Therefore, direct numerical simulations were used in the past employing the low-Mach assumption with a finite volume code. As a next step, we extend the discontinuous Galerkin spectral element method for direct numerical simulation of supercritical carbon dioxide. The higher-order of accuracy and fully compressible code improve the fidelity of the simulations. A computationally robust and efficient implementation of the equation of state was used which is based on adaptive mesh refinement. The objective of this report is to demonstrate the usage of the code in complex flow. Therefore, channel geometry is adopted and simulations were conducted at different Mach numbers to observe the effects of compressibility in the supercritical fluid regime. The isothermal boundary conditions were used at the walls of the channel. The mean profile of pressure, density and temperature are drastically affected by the Mach number variation. In the end, scalability tests were conducted and code shows a very good parallel scalability up to 12,000 cores.