On the computation of turbulent backstep flow

This paper discusses the computation of turbulent backstep flow, focusing on the use of Reynolds stress models. A review of existing backstep calculations shows that these calculations generally underpredict reattachment length, and some calculations produce physically unrealistic behavior. Some of these problems are shown to be related to the commonly used pressure-strain coefficients, particularly the linear return-to-isotropy coefficient, C₁. A new expression for C₁ that is consistent with both homogeneous shear flow experiments and return-to-isotropy experiments produces reasonable results in the present backstep calculations. Some of the present backstep calculations result in unsteady periodic vortex shedding consistent with experimental evidence. This presents a dilemma in the context of Reynolds averaging, which is discussed.