The laminar wake behind a 6:1 prolate spheroid at 45° incidence angle Available to Purchase

The wake behind a 6:1 prolate spheroid at 45° angle of attack has been studied. The three-dimensional unsteady Navier-Stokes equations have been solved numerically for Reynolds numbers Re = 50, 200, and 1000, where Re is based on the inflow velocity U₀ and the minor axis D of the spheroid. The wake at the two lowest Reynolds numbers is steady and symmetric about the meridional plane. Even at Re = 1000 the near-wake, which is dominated by vortex sheets separated from the spheroid, is still steady and symmetric except in a very limited region of size 0.2D near the tip of the spheroid. However, the intermediate wake, which extends from 4D downstream of the spheroid, is distinctly asymmetric and exhibits local oscillations with an amplitude below 1% of U₀. The intermediate part of the wake consists of a pair of counter-rotating vortices and the wake is deflected to the side of the strongest vortex, whereas the other vortex is partially wrapped around. It is conjectured that the wake at this particular Reynolds number is on the verge of becoming unsteady. Nevertheless, the forces and torques on the prolate spheroid show no sign whatsoever of asymmetry or unsteadiness. The resulting drag coefficients compare to within 30% with the Hölzer-Sommerfeld correlation.