Vorticity Contours; Mixing Within a Cylindrical Container (6.4 MB file size)

Contours of constant vorticity magnitude on a plane within a mixing vessel computed using a multiple reference frame, sliding mesh model and the volume of fluid method. Tank volume is 250L; impeller running at 118 RPM.

The Vortex Breakdown movie shows iso-vorticity surfaces evolving in time (at a Reynolds number of 200). The early frames reveal an initially symmetric bubble-like structure which contains a region of reversed flow. An instability originates in the the "tail" emanating from the aft portion of the bubble. A transition to spiral-type breakdown then ensues.

Mixed convection in a horizontal duct; vorticity contours (497 KB)

Mixed convection in a horizontal rectangular duct of aspect ratio 4 heated from below, and with cold side walls, was studied numerically for a non-Boussinesq fluid. Results were computed for a Rayleigh number of 130,700, a reduced temperature of 2.33, and Reynolds numbers ranging from 5 to 20. The movie listed above reveals the time-dependent evolution of the flow at Re=5 in terms of contours of constant vorticity. (Flow from left to right, top view of the duct.) The sequence reveals that the inner vortex pair terminates upon itself, or form distinct ring vortices. The consequence of these coherent structures is a complex time-dependent distrubution of the Nusselt number on the lower wall.

Buoyant, pulsating exhange flow through a vent in a horizontal partition; density contours (788 KB)

Buoyancy-driven exchange flow between compartments in a cylindrical take separated by a vented, horizontal partition of finite thickness (vent diameter to partition thickness ratio of L/D=0.3). Results were computed for water with density variation achieved through temperature differentials. At t=0, the temperature of the water in the lower and upper partitions was set to 320 and 295 K, respectively.