Assessment of Turbulence Models for Turbulent Flow over Backward Facing Step

Predication of reattachment length of separated shear layers in low Reynolds number turbulent flow is a challenging task to evaluate the capabilities of different turbulence models, especially for MEMS applications. Physical significances of backward facing step and its industrial applications were discussed. Flow analysis of backward facing step in 2D as well as in 3D were carried out by using Finite volume method, incompressible segregated scheme with SIMPLE algorithm for pressure velocity coupling. Although the recirculation created by backward facing step (BFS) is predicted by all turbulence models but ε based turbulence models underpredict the reattachment length of flow where as Shear Stress Turbulence model accurately predict the flow reattachment. Comparison of 3D and 2D results revealed that the separation point is fixed where as the reattachment points were different due to 3D nature of turbulence.