Date of Award

Fall 2015

Project Type


Program or Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

First Advisor

John P. McHugh

Second Advisor

John P. McHugh

Third Advisor

Gregory P. Chini


A horizontal distributed vortex in a stratified fluid is treated using direct numerical simulations. The strength of the vortex is uniform but antisymmetric about the centerline such that the total circulation is zero, as with airplane wings. This distributed vortex allows the density field and velocity field to evolve together, as happens in real flows behind lifting surfaces. The numerical approach is spectral in space with periodic horizontal directions and a projection method in time using the 3rd order Adams-Bashforth method. The primary parameter is the Froude number. For large Froude number, the distributed vorticity quickly rolls up and forms a vortex pair, approximately matching cases initiated as a fully-developed vortex pair. For small Froude number, both cases disintegrate into internal waves. It is found here that the critical Froude number with a distributed vortex is much larger than previously thought. The results also show that distributed vortex exhibits a strong vertical oscillation with frequency that is approximately the buoyancy frequency N. Late in the simulations, the flow degenerates into small-scale motion.

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