Numerical analysis of air flow around a wall mounted hemisphere with different turbulence models

Prediction of flow around surface mounted obstacles with different sizes and shapes is one of the considerable applications of computational fluid dynamics. Flow separation, recirculation, generation of several vortices, interaction of boundary layer with three-dimensional shear layers, unsteady nature of flow with strong vortex shedding are some of the most important features of such complex flow fields. These features produce complexities in the accurate numerical simulations of this type of flow, which affect on pressure distribution and heat transfer from the obstacle to the surrounding fluid flow.In the present study, turbulent air flow around a surface mounted hemisphere is investigated numerically. The flow field has been simulated using RNG k-ε turbulence model as well as Large Eddy Simulation (LES) technique. Using numerical results, variations of flow velocity at various sections along the midplane of the hemisphere are presented and compared with the wind tunnel measurements. It is shown that LES is capable to capture the complex features of the flow especially in the separation bubble forms behind the hemisphere while different turbulence models are not able to predict flow pattern over and behind the hemisphere accurately. Using LES result various countors of streamlines and vorticity at different sections are plotted.

Keywords:

Hemisphere , LES , Turbulent flow ,