A STRESS-STRAIN LAG EDDY VISCOSITY MODEL FOR UNSTEADY MEAN FLOW

摘要

A new eddy viscosity model is proposed to include stress-strain lag effects in the modelling of unsteady mean flows. A transport equation for the lag parameter, hereby denoted C_(as) is derived from a full Reynolds Stress Model (RSM), to be solved in conjunction with a standard two equation low Reynolds number Eddy Viscosity Model (EVM). The performance of the new k — ε — C_(as) model is compared to the flow in a channel driven by a pressure gradient oscillating around a non-zero mean. Results are compared with Large Eddy Simulations (LES) of the same flow and the addition of the lag parameter equation is shown to give improved results when compared to the standard EVM.