Flow over backwards facing steps are classic computational fluid dynamics test problems, and are often used for validation of simulation codes. This test problem consists of studying how the flow field reacts to a sudden expansion in a channel. The expansion will cause a break in the flow and a recirculation or separation zone will form. To validate the results the computed length of the recirculation zone is compared with the experimental results of Pitz and Daily [1].
In this example the stationary incompressible Navier-Stokes equations are used to model the fluid with simulation parameters corresponding to a Reynolds number, Re = 18145. The flow is therefore fully turbulent, whereby a turbulence model closure must also be applied. Here the standard k-epsilon turbulence model is used which is available with the external OpenFOAM CFD solver integration.
This model is available as an automated tutorial by selecting Model Examples and Tutorials… > Fluid Dynamics > Turbulent Flow Over a Backwards Facing Step from the File menu. Or alternatively, follow the video tutorial or step-by-step instructions linked below.
Reference
[1] R.W. Pitz and J.W. Daily, Combustion in a Turbulent Mixing Layer Formed at a Rearward Facing Step, AIAA Journal 21, 1983.