Bishakhdatta Gayen

Large eddy simulation of a stratified boundary layer under an oscillatory current

A numerical study based on large eddy simulation is performed to investigate a bottom boundary layer under an oscillating tidal current. The focus is on the boundary layer response to an external stratification. The thermal field shows a mixed layer that is separated from the external stratified fluid by a thermocline. The mixed layer grows slowly in time with an oscillatory modulation by the tidal flow. Stratification strongly affects the mean velocity profiles, boundary layer thickness and turbulence levels in the outer region although the effect on the near-bottom unstratified fluid is relatively mild. The turbulence is asymmetric between the accelerating and decelerating stages. The asymmetry is more pronounced with increasing stratification. There is an overshoot of the mean velocity in the outer layer; this jet is linked to the phase asymmetry of the Reynolds shear stress gradient by using the simulation data to examine the mean momentum equation. Depending on the height above the bottom, there is a lag of the maximum turbulent kinetic energy, dissipation and production with respect to the peak external velocity and the value of the lag is found to be influenced by the stratification. Flow instabilities and turbulence in the bottom boundary layer excite internal gravity waves that propagate away into the ambient. Unlike the steady case, the phase lines of the internal waves change direction during the tidal cycle and also from near to far field. The frequency spectrum of the propagating wave field is analysed and found to span a narrow band of frequencies clustered around 45°.

Algebraic and exponential instabilities in a sheared micropolar granular fluid

Based on a micropolar continuum of rough granular particles that takes into account the balance equations for the spin (/rotational) velocity and the spin granular temperature, the linear stability characteristics of an unbounded shear flow (

Topographic influence on submesoscale dynamics in the Southern Ocean

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Orientational correlation and velocity distributions in uniform shear flow of a dilute granular gas.

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Negative turbulent production during flow reversal in a stratified oscillating boundary layer on a sloping bottom

x

PSI to turbulence during internal wave beam refraction through the upper ocean pycnocline

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Convection Enhances Mixing in the Southern Ocean

y

Turbulent Convection Insights from Small-Scale Thermal Forcing with Zero Net Heat Flux at a Horizontal Boundary.

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Direct and large-eddy simulations of internal tide generation at a near-critical slope

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Turbulence during the generation of internal tide on a critical slope

are the streamwise, transverse and spanwise directions, respectively, and