Abstract
A backward facing step (BFS) flow has been investigated extensively by the research community experimentally and computationally due to its significant flow features because of the presence of the separation-reattachment mechanism. The strength of this mechanism varies based on the Reynolds number (RN). For turbulent flow at low RN, the separation-reattachment mechanism computations may be expensive due to high requirements of fine grid which varies based on the employed turbulence model. Several classes of turbulence models have been attempted for capturing complex fluid flow phenomena, namely zero, one, two, three, four and seven equation models. Selected turbulence models from each class have been employed in this paper in order to predict the reattachment length behind BFS at RN of 37,000. The grid independent solution is obtained using modified general Richardson method based on three relatively coarse grids which significantly reduces the computational cost. It is found that the predicted reattachment length for employed turbulence models agrees well with experiment and is considered as a grid independent solution. The visualization of computational domain on the wind tunnel shows similar trends for flow developed in the region of reattachment length. This work can substantially reduce cost of computations for the prediction of reattachment length in BFS flow problem and shows how closely turbulence models perform when grid independent solution is obtained.