scholarly journals Eulerian and Lagrangian Parameterization of the Oceanic Mixed Layer using Large Eddy Simulation and MPAS-Ocean

2018 ◽  
Author(s):  
Luke Van Roekel
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Oceanic Mixed Layer ◽  
Eddy Simulation ◽  
Large Eddy

Representing Sheared Convective Boundary Layer by Zeroth- and First-Order-Jump Mixed-Layer Models: Large-Eddy Simulation Verification

2006 ◽  
Vol 45 (9) ◽  
pp. 1224-1243 ◽  
Author(s):  
David Pino ◽  
Jordi Vilà-Guerau de Arellano ◽  
Si-Wan Kim
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Mixed Layer ◽  
Convective Boundary ◽  
First Order ◽  
Eddy Simulation ◽  
Jump Model ◽  
Large Eddy ◽  
Entrainment Zone ◽  
Convective Boundary Layers

Abstract Dry convective boundary layers characterized by a significant wind shear on the surface and at the inversion are studied by means of the mixed-layer theory. Two different representations of the entrainment zone, each of which has a different closure of the entrainment heat flux, are considered. The simpler of the two is based on a sharp discontinuity at the inversion (zeroth-order jump), whereas the second one prescribes a finite depth of the inversion zone (first-order jump). Large-eddy simulation data are used to provide the initial conditions for the mixed-layer models, and to verify their results. Two different atmospheric boundary layers with different stratification in the free atmosphere are analyzed. It is shown that, despite the simplicity of the zeroth-order-jump model, it provides similar results to the first-order-jump model and can reproduce the evolution of the mixed-layer variables obtained by the large-eddy simulations in sheared convective boundary layers. The mixed-layer model with both closures compares better with the large-eddy simulation results in the atmospheric boundary layer characterized by a moderate wind shear and a weak temperature inversion. These results can be used to represent the flux of momentum, heat, and other scalars at the entrainment zone in general circulation or chemistry transport models.

scholarly journals Large eddy simulation of particle settling in the ocean mixed layer

2006 ◽  
Vol 18 (8) ◽  
pp. 085109 ◽  
Author(s):  
Y. Noh ◽  
I. S. Kang ◽  
M. Herold ◽  
S. Raasch
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Ocean Mixed Layer ◽  
Particle Settling ◽  
Eddy Simulation ◽  
Large Eddy

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

2009 ◽  
Vol 643 ◽  
pp. 233-266 ◽  
Author(s):  
BISHAKHDATTA GAYEN ◽  
SUTANU SARKAR ◽  
JOHN R. TAYLOR
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Numerical Study ◽  
Bottom Boundary Layer ◽  
Mean Velocity ◽  
Bottom Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean

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°.

Large Eddy Simulation of Dust Devils in a Diurnally-Evolving Convective Mixed Layer

1500 ◽  
Vol 999991 (9991) ◽  
pp. 9963-9977 ◽  
Author(s):  
Junshi dummyITO ◽  
Ryo dummyTANAKA ◽  
Hiroshi dummyNIINO ◽  
Mikio dummyNAKANISHI
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Dust Devils ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Convective Mixed Layer

Large-Eddy Simulation of Deep-Cycle Turbulence in an Equatorial Undercurrent Model

2013 ◽  
Vol 43 (11) ◽  
pp. 2490-2502 ◽  
Author(s):  
Hieu T. Pham ◽  
Sutanu Sarkar ◽  
Kraig B. Winters
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Buoyancy Frequency ◽  
Surface Mixed Layer ◽  
Equatorial Undercurrent ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Model Components ◽  
Surface Buoyancy ◽  
Les Model

Abstract Dynamical processes leading to deep-cycle turbulence in the Equatorial Undercurrent (EUC) are investigated using a high-resolution large-eddy simulation (LES) model. Components of the model include a background flow similar to the observed EUC, a steady westward wind stress, and a diurnal surface buoyancy flux. An LES of a 3-night period shows the presence of narrowband isopycnal oscillations near the local buoyancy frequency N as well as nightly bursts of deep-cycle turbulence at depths well below the surface mixed layer, the two phenomena that have been widely noted in observations. The deep cycle of turbulence is initiated when the surface heating in the evening relaxes, allowing a region with enhanced shear and a gradient Richardson number Rig less than 0.2 to form below the surface mixed layer. The region with enhanced shear moves downward into the EUC and is accompanied by shear instabilities and bursts of turbulence. The dissipation rate during the turbulence bursts is elevated by up to three orders of magnitude. Each burst is preceded by westward-propagating oscillations having a frequency of 0.004–0.005 Hz and a wavelength of 314–960 m. The Rig that was marginally stable in this region decreases to less than 0.2 prior to the bursts. A downward turbulent flux of momentum increases the shear at depth and reduces Rig. Evolution of the deep-cycle turbulence includes Kelvin–Helmholtz-like billows as well as vortices that penetrate downward and are stretched by the EUC shear.

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