Mazyar Dawoodian - Iran-Sanandaj, University of Kurdistan

In this paper, a 3D flow field around a bluff body (Hemi-spherical cup) in an incompressible fluid is modelled. On the top of the bluff body at its apex a vent of air is inserted. The Reynolds number is varied from 39000 to 390000. Two flow conditions are considered in this study. At first, the flow is taken to be steady and then unsteady. In both of them the flow is turbulent. Coefficients of drag were determined. With comparing two conditions, it can be seen that in the parachute without vent and with 5% vent to Reynolds about 200000 there is no notable difference between steady and unsteady conditions, but by increasing Reynolds number this difference is more notable. This phenomenon occurs after this Reynolds number and it is because of the unsteady flow in Reynolds number more than 200000.

Drag Coefficient, Reynolds Number, Vent Ratio