Reliability Issues of LES-Related Approaches in an Industrial Context

Abstract

Large-Eddy Simulation (LES), Detached-Eddy Simulation (DES) and Scale-Adaptive Simulation (SAS) are increasingly being used as engineering tools to predict the behaviour of complex industrial flows. Often the flows studied have not been examined previously and the required grid resolution is unknown. Industrial users studying these flows tend to be using commercial CFD codes and do not usually have access to high-performance computing facilities. Due to the significant computing times required, it is difficult to undertake systematic grid-dependence studies. There is therefore a risk that LES, DES and SAS will be performed using overly coarse grids which may lead to unreliable predictions. The present work surveys a number of practical techniques that provide a means of assessing the quality of the grid resolution in large-eddy simulations and related approaches. To examine the usefulness of these techniques, a gas release in a ventilated room is examined using DES and SAS. The grid resolution measures indicate that overall the grids used are relatively coarse. Both DES and SAS model predictions are found to be in poor agreement with experimental data compared to steady and unsteady Reynolds-averaged Navier–Stokes (RANS) results using the SST model. The SAS model also shows the greatest grid sensitivity of the four models tested. The work highlights the need for grid-dependence studies and the potential problems of using coarse grids.