Flow over a backward facing step using CONVERGE CFD

Aim- To investigate the effect of varying grid size on the physical quantities of the fluid and its flow domain.

Procedure- A backward step is created in converge with the following dimensions given in the below figure. Air is the fluid flowing through the domain with the pressure difference of 9000 pa between the inlet and outlet boundaries. The pressure based steady solver is used for the simulation. The initial pressure and temperature in the domain is 1 bar and 300 K. The RNG-K EPSILON turbulence model is used. The effect of mesh size is studied in this project. This project is usually carried out to study the effect of a turbulence model.

Three different mesh sizes 1) 0.003 m 2) 0.002 m 3) 0.0025 m are used in the simulation.

The above velocity vector is for 0.002 m mesh size.

The blue region indicates the re-circulation zone due to low static pressure. The heat transfer increases in the re-circulation region due to the increase in the convective heat transfer coefficient.

Grid independence study confirms that the results of the analysis are not affected by change in the mesh size.However fine meshing is required whenever the physical quantities are very sensitive to the time and the flow domain.