Crossflow past a prolate spheroid at Reynolds number of 10000

Abstract

The flow field around a 6:1 prolate spheroid has been investigated by means of direct numerical simulations. Contrary to earlier studies the major axis of the spheroid was oriented perpendicular to the oncoming flow. At the subcritical Reynolds number 10 000 the laminar boundary layer separated from the frontal side of the spheroid and formed an elliptical vortex sheet. The detached shear layer was unstable from its very inception and even the near-wake turned out to be turbulent. The Strouhal number associated with the large-scale shedding was 0.156, significantly below that of the wake of a sphere. A higher-frequency mode was associated with Kelvin–Helmholtz instabilities in the detached shear layer. The shape of the near-wake mirrored the shape of the spheroid. Some 10 minor diameters downstream, the major axis of the wake became aligned with the minor axis of the spheroid.