view:45117 Last Update: 2021-9-11
Behrad Zeinali, Jafar Ghazanfarian
Turbulent Flow over Partially Superhydrophobic Underwater Structures: The Case of Flow over Sphere and Step
Results of the large eddy simulations (LES) over two partially superhydrophobic 3D geometries, including the backward-facing step and the sphere at the Reynolds number of 400, 1000, 2000 have been presented using the open-source OpenFOAM C++ libraries. The effect of imposing the locally partial-slip on the surface of the mentioned cases has been investigated. The results confirmed that the superhydrophobicity decreases the drag coefficient and increases the Strouhal number of the sphere by up to 46% and 25%, respectively. In the meantime, the superhydrophobic backward-facing step experiences an increment of almost 4% and 3% in both the reattachment length placement and the recirculation length, respectively. In addition, the results have been analyzed to improve the model's efficacy by locating the region on the geometry's surface with a dominant role on the resulting vicissitudes of the drag coefficient, the Strouhal number, and the reattachment length. To obtain such an optimum model, the shear stress distribution diagram on the surface of the geometries have been studied. It is found that the areas with utmost changes in the shear stress were half of the sphere that faces the flow and the side of the step that the flow reattaches to it.