Numerical simulations of the near wake of a sphere moving in a steady, horizontal motion through a linearly stratified fluid at Re = 1000

A numerical investigation of the near wake of a sphere moving horizontally through a linearly stratified fluid is presented. Simulations are first performed on a flow with Reynolds number Re = 200 for a range of internal Froude number, 0.1 ≤ Fr ≤ ∞. The simulations capture buoyant characteristic behavior, the presence of vortex shedding at low Fr, and lee waves. Simulations at higher Reynolds number, Re = 1000, for 1 ≤ Fr ≤ ∞ provide a description and parametrization of the near wake, including the density field. At Re = 1000, the effects of utilizing two different averaging techniques in the unsteady near wake region are discussed. Perturbation quantities in the stratified near wake are anisotropic, and based on the oscillations of the centerline vertical perturbation velocity, the Fr at which the stratified near wake may be considered indistinguishable from the uniform density near wake is suggested to be O(100). Parametrization of the near wake is accomplished using the parameterized vertical wake height, downstream distance from the sphere, and Fr as parameters.