Some Comments on the Modeling of the Turbulent Wake of a Self-propelled Body in a Stratified Fluid

The modeling of the turbulent wake of a self-propelled body in a stratified fluid is discussed. The scaling parameter is taken to be the internal Froude number, using the speed and diameter of the body and Vaisala frequency of the fluid. Arguments are presented to suggest that the ratio of the time for the wake to collapse to the characteristic time of the turbulence is invariant with model scale if the wake is turbulent up to and including the collapse. A number of criteria for the existence of a turbulent wake are discussed. Numerical estimates are made, assuming typical values of the model speed and of the Vaisala frequency, of the minimum model size necessary for the existence of a turbulent wake at collapse.