Abstract
Turbulent Mixing in buoyancy-driven stratified flow can be most accurately represented by two non dimensional parameters: ‘entrainment rate (E)’ and ‘mixing efficiency (µ)’. This study investigates the differences in mixing between 2-D and 3-D dense currents, with a bottom slope up to 100 for a wide range of Reynolds (1500 < Re < 17000) by employing high-resolution Large Eddy Simulations (LES). For given initial conditions, the instantaneous Froude’s number for 2-D simulation is equivalent to that from 3-D simulation in the slumping phase. However, the E in the former is up to twice as large as that in the latter, which ranges from 0.02 < E < 0.1. The results demonstrate strong correlations of E and µ with Re, within the wide span of Re cases, for subcritical Fr within 0.50-.65. It is further shown that µ values are in the range of 0.11 ± 0.02 for 3-D and 0.14 ± 0.01 for 2-D lock-exchange cases, which is smaller than the value of 0.2 that is extensively used by the oceanography community to compute mixing in the ocean. Differences in mixing behavior exist between lock-exchange and dense overflow density current systems.
Citation
Nayamatullah M and Bhaganagar K. Turbulent Mixing in 2-D and 3-D Density Currents over a Slope. SM J Biol. 2017; 3(1): 1016s.