Low-Reynolds-Number One-Equation Turbulence Model with Mixed Time-Scale for Complex Flows

Abstract

To perform massive and unsteady calculations of flow fields, the hybrid RANS/LES method is very useful, in which a RANS is employed near the wall, and an LES is carried out in the region away from the wall. However, to calculate adequately near-wall turbulent motions over complex terrain, a number of grids are needed near the wall. Thus, to reduce the calculation load when predicting real flow fields by computer, solving fewer transport equations is recommended. Therefore, in this study, we construct a low-Reynolds-number (LRN) one-equation model for eddy viscosity by introducing a time-scale based on the velocity gradient parameter. This time-scale has proven very effective for predicting local flows over complex terrain. The proposed model is evaluated in complex turbulent flows, such as backward-facing step flow, forward-facing step flow, flow past a two-dimensional bock and flow over a curved hill. The predicted results are compared with available experimental data. It is shown that the proposed one-equation model reproduces the results generally in good agreement with experimental data.