Effect of Roughness on Entrainment of Turbulent Buoyant Flows *

Interaction of heavy density fluid with a buoyant, ambient environment results in the formation of bottom-propagating 3D turbulent density current. A large-eddy simulation (LES) is performed for lock-exchange release density currents over rough walls to better understand the effect of roughness on turbulent density currents. A finite volume method is implemented to solve Navier-Stokes equations using Boussinesq approximations. A special case of the immersed-boundary method called volume-penalization is performed to comprehend the bottom-mounted rough topology. The effect of regular and irregular roughness shapes is investigated for cubical and cylindrical roughness elements.  The effect of Reynold’s number, frictional Reynolds number, and Froude’s number on the entrainment coefficient has been studied to provide a universal framework on the effect of roughness in entrainment.