Effect of ellipsoid aspect ratio on wake

• The paper presents ellipsoid flow structures for AR = 1 – 6 and Re = 300 and 3700. • Five distinct flow regimes are identified. • Both AR and Re play critical roles in fluid forces and wake. • As AR is increased, the pressure drag coefficient decreases while the friction drag increases. • With increasing AR , boundary layer thickens, flow separation is delayed, and wake width narrows. The paper presents a numerical study on the wake of an ellipsoid with aspect ratios of AR = 1 – 6 at Reynolds numbers of Re = 300 and 3700, aiming to investigate the effect of AR on both the turbulent and laminar wake behavior. Five distinct flow regimes are identified based on the flow structures, vortex shedding frequency, fluid forces, boundary layer, wake size, and wake development. Both AR and Re play critical roles in determining fluid forces, boundary layer characteristics, wake size, and wake development and dynamics. As AR is increased, the pressure drag coefficient decreases while the friction drag coefficient increases. Consequently, the total drag coefficient initially decreases with increasing AR before rising again. With increasing AR , the boundary layer thickens, flow separation is delayed, the wake width narrows, the recirculation bubble shrinks, and the velocity deficit declines. When Re is increased, the boundary layer narrows, the flow separation occurs earlier, and the recirculation bubble elongates. In the near wake, turbulent kinetic energy and enstrophy are initially high, but both decrease as AR increases. This reduction is attributed to the weakening of vortices and the narrowing of the wake.