Experimental study of the Reynolds number dependence of a sphere wake at fixed Froude number

Wakes in density-stratified fluids radiate internal waves due to the random turbulent motions in the core of the wake (Meunier et al. JFM 2018; Rowe, Diamessis, and Zhou JFM 2020). To investigate the relationship between the core turbulent wake and the resulting internal waves, experiments with a dimpled sphere were conducted using particle image velocimetry. The Reynolds number was varied between 50,000 and 100,000 to investigate how wake characteristics would scale up and down and all experiments were conducted with a Froude number of about 80. The experiments extend prior unstratified wake results of Saunders et al. (PRF 2020; Exp. Fluids 2022) to the stratified regime. This presentation will focus on the core turbulent wake behind the sphere out to and the radiated internal waves extending to a dimensionless time of Nt ~ 50, where N is the buoyancy frequency.