Penetration by a negatively buoyant vortex ring

Abstract

In order to investigate the vortex motion affected by buoyancy force, we experimentally formed a negatively buoyant vortex ring by pushing less dense fluid vertically downward out of a nozzle and measured the penetration depth of it in the wide Reynolds number range, 3,000 < Re < 30,000. We confirmed that the penetration depth of negatively buoyant vortex rings generally depends only on the Froude number and it is larger than that of the jet for the same Froude number in the range of Fr > 2. The formation conditions of buoyant vortex rings to be turbulent or laminar are also examined, since the characteristic features of buoyant turbulent vortex rings are markedly different from those of buoyant laminar rings.