A numerical investigation of laminar flow over a backward facing inclined step

The aim of the present study is to analyze the two dimensional flow over a backward-facing-inclined step in laminar flow regime. The inspiration for the present work is derived from the fact that in automobile industry, analyzing the flow over an inclined step shall help in understanding the characteristics of the rear vehicle wake. A considerable percentage of the energy needed to propel the vehicle is dissipated by the vorticity generated in the rear of the vehicle, hence it is of utmost importance to understand the properties of the wake. In the present paper, the flow over a backward step is initially analyzed and the results are compared with the existing literature to validate the code developed. The inclined step simulations were carried out by varying different aspects of the geometry i.e. different tilts, several upstream lengths and a range of different Reynolds numbers. Critical Reynolds numbers for vortex shedding in the wake of different step inclinations have been analyzed for all cases studied. A discussion on the time-averaged drag and lift coefficients as a function of Reynolds number and for all cases undertaken, are among the results presented. Among the conclusions, it is particularly interesting to point out that the inclination angle of 15° was found to be the critical angle for vortex shedding, after which critical Reynolds number remains constant.