Numerical Analysis of Turbulent Density Current Over Rough Surfaces Using Large Eddy Simulation

Bhattarai, Ishan
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Turbulent density currents are an important class of buoyancy-driven flows that arise as a heavier density fluid enters a lighter density ambient environment, mixes with the ambience resulting in the formation of density fronts. The horizontally traveling density currents or fronts are of important consequence for oceanic mixing and atmospheric pollution dispersion. A large-eddy simulation was performed on a lock-exchange release of density currents through smooth andrough walls to understand the effect of roughness on density currents. An immersed boundarybased volume penalization approach was implemented in which solid regions were represented as a porous medium with vanishing permeability. To understand the effects of the roughness on the flow, the incompressible Navier-Stokes equations were solved with Boussinesq approximations in a finite volume formulation. Cylindrical, pyramidal, and cubical roughness structures were used to characterize the behavior of the flow. The focus of the study is analyzing these threedimensional turbulent bottom-propagated density currents generated by a lock exchange release mechanism. The bottom roughness on which these currents propagate significantly influences the extent and mixing within the current due to the entrainment of the ambient fluid. The affect of mixing, Reynolds number, and Froude number was studied to provide a universal framework on the effect of roughness in density currents.

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density current, gravity current
Mechanical Engineering