Forces and torques on a prolate spheroid: low-Reynolds-number and attack angle effects

The three-dimensional flow field around a prolate spheroid has been obtained by integration of the full Navier-Stokes equations at Reynolds numbers 0.1, 1.0, and 10. The 6:1 spheroid was embedded in a Cartesian mesh by means of an immersed boundary method. In the low-Re range, due to the dominance of viscous stresses, an exceptionally wide computational domain was required, together with a substantial grid refinement in the vicinity of the surface of the immersed spheroid. Flow fields in equatorial and meridional planes were visualized by means of streamlines to illustrate Reynolds number and attack angle effects. Drag and lift forces and torques were computed and compared with the most recent correlation formulas. The largest discrepancies were observed for the moment coefficient, whereas the drag coefficient compared reasonably well.