EPTT 2022

13th Spring School on Transition and Turbulence

Turbulent kinetic energy budget in the mixing layer of a gravity current

Submission Author: Sara Mata , RS
Co-Authors: Sara Mata, Jorge Silvestrini
Presenter: Sara Mata

doi://10.26678/ABCM.EPTT2022.EPT22-0032

 

Abstract

Density hyperpycnal currents are flows of a denser fluid running below a lighter fluid due to density gradient. A mixing zone is developed in the fluid interface, where complex structures are generated by shear, buoyancy, and turbulence interaction, triggering processes like entrainment and mixing. At large Reynolds number (Re), density currents are fully turbulent. It is possible to delimit the mixing layer based on vorticity criterion, which identifies the layer position where the spanwise vorticity ωz , is positive. The inner border is the vertical position where ω z changes sign, and the diffuse outer border is chosen where ωz achieves 5% of the maximum vorticity. This study simulated conservative density currents in lock-release configuration for Re=3450 and 8950, using Direct Numerical Simulation and Implicit Large Eddy Simulation, respectively. It is used the high-order flow solver Xcompact3d to solve a Boussinesq system on a Cartesian mesh. The statistical approach is applied to calculate fluctuations velocity via Reynolds decomposition for slumping, inertial and viscous phases. It delimited the mixing layer to compare with the turbulent kinetic energy peaks and shear production, dissipation, and buoyancy values for all the simulation times. The influence of the Re number on the evolution of the mixing layer turbulent structures are analyzed.

Keywords

Gravity hyperpycnal currents, lock-release configuration, mixing layer, turbulent structures, Budget of Turbulent Kinetic Energy

 

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