Large eddy simulation of stratified flow past prolate spheroids with varying aspect ratios

This study employs large eddy simulation and the Boussinesq approximation to investigate the characteristics of wakes generated by prolate spheroid with different aspect ratios (length-to-diameter ratios, L/D = 1.0, 1.5, 2.0, 3.0) in a linear stratified flow, with the Reynolds number (Re) of 3700 and the Froude number (Fr) of 3. The research primarily focuses on the effects of different aspect ratios on defect velocity, wake length scales, root mean square values of velocity components, power spectra, wake energy, and turbulent kinetic energy (TKE). The findings show that the defect velocity along the wake centerline follows the relationships: u ∼ (x/D)−0.08 (L/D = 1.0), as the aspect ratio increases, the exponent gradually decreases, indicating a shorter mean lifespan of the wake. After the starting position of the accelerated collapse stage, the half-width, half-height, the ratio of half-height to half-width, and the influence area of the wake oscillate periodically. With the aspect ratio increases, the half-width, half-height, the ratio of half-height to half-width, and the influence area of the wake are gradually becoming smaller, and the Reynolds stress gradually decreases in magnitude and becomes concentrated near the centerline of the wake. The turbulent kinetic energy for different aspect ratios follows the relationship TKE ∼ (x/D)−1.19. The mean kinetic energy, turbulent kinetic energy, and turbulent potential energy (TPE) of the wake all decrease with increasing aspect ratio. Both the energy of wake and transport, advection, and buoyancy terms in turbulent kinetic energy budget exhibit periodic oscillations, with the oscillation wavelength corresponding to half a buoyancy period (π·Fr). All terms in turbulent kinetic energy budget decrease with the aspect ratio increases.