Numerical experiments on stratified spin-up

Numerical experiments were performed for the spin-up of a stratified Boussinesq fluid in a right cylinder. The so-called “corner jet,” postulated in earlier analytical treatments by Walin, is found to have an inclination which oscillates between near-horizontal to near-vertical positions. The net effect is that some of the fluid spends more time in viscous boundary layers before entering the interior than if the jet were inclined at a steady angle to the vertical. This accounts for the shorter experimentally observed spin-up times and for the discrepancy between theory and experiments.