Development of a high-order solver for large eddy simulation of turbulent heat transfer at supercritical pressure based on Nek5000

Abstract

Turbulent heat transfer at supercritical pressure is a complex flow phenomenon due to drastic variations in fluid properties near the pseudocritical point. Numerical simulation is an important method to reveal the underlying physics. Currently, low-order numerical methods together with Reynolds-averaged Navier–Stokes equations are the mainstream in which empirical parameters are required, preventing high-fidelity simulations. Through inventing iterative properties updating and density-weighted explicit filtering, this work develops a high-order spectral element solver based on the open-source code Nek5000. By simulating a classical problem of supercritical CO2 flowing in a heated pipe and comparing it with benchmark data, the capability of the solver in direct numerical simulation is validated. Further results suggest lowering the mesh resolution leads to inaccurate predictions of bulk parameters and turbulent statistics. Therefore, filtering-based large eddy simulation (LES) is explored with different filter weights under a coarse mesh. Results show such a method can significantly improve most of the bulk parameters, including the bulk Nusselt number. The optimal filter weight can be determined from a simple optimization problem minimizing the deviation of overall energy conservation. Being high-order and capable of LES without empirical parameter, the current solver is a powerful tool for high-fidelity simulation of turbulent heat transfer at supercritical pressure.