DNS Simulation of Dry Thermals

The two animations below show the vertical velocity (left panel) and density perturbation (right panel) of a dry, buoyant parcel (or "thermal") rising through a neutrally stratified environment, for both laminar and turbulent cases (left and right animations, respectively). The thermals take the form of buoyant vortex rings, which appear as disconnected lobes in these 2-D cross sections of fully 3-D simulations, performed with Dedalus. The black line defines the thermal's control volume, and is defined such that the average vertical velocity within equals the velocity of the thermal's top. The mixing or "entrainment" of environmental fluid into these thermals, which is surprisingly similar between the laminar and turbulent cases, is studied in Lecoanet and Jeevanjee (2019). A simple model for how this entrainment interacts with the thermals' dynamics is given in McKim, Jeevanjee, and Lecoanet (2019).