Axisymmetric intrusive gravity currents in linearly stratified fluids

Two detailed field experiments were performed to investigate the spreading dynamics of axisymmetric, inertia-buoyancy controlled, intrusive gravity currents in linearly stratified environments. The appropriate intrusions were successfully generated using deep-set point-source bubble plume devices installed within different thermally-stratified reservoirs. The intrusive flows were found to progress at a rate predicted from a simple inertia-buoyancy force balance with the intrusion thickness decreasing with distance from the source. The results imply that shear waves of all modes were generated at the intrusion nose and able to propagate away to modify the flow field. Turbulent activity, internal to the intrusions, was found not to influence the spreading characteristics. Scaling arguments and the experimental findings were also used to derive a parameter describing the initial intrusion dynamics. By combining the current findings with previously published results for intrusions progressing in the viscous-buoyancy regime, a relation describing the distance at which viscous forces become dominant was derived.