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

scholarly journals Examination of the Mixed Layer Deepening Process during Convection Using LES

2010 ◽  
Vol 40 (9) ◽  
pp. 2189-2195 ◽  
Author(s):  
Yign Noh ◽  
Gahyun Goh ◽  
Siegfried Raasch
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Richardson Number ◽  
Mixed Layer Depth ◽  
Inertial Oscillation ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Simulation Data ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Analysis of large-eddy simulation data of the ocean mixed layer under convection reveals that the contribution from wind stress decreases with time as a result of inertial oscillation in the extratropical ocean and that it leads to a rapid increase of the bulk and gradient Richardson number at the mixed layer depth. The criteria for the mixed layer deepening in the widely used mixed layer models, such as the Niiler–Kraus (NK) model, the Price–Weller–Pinkel (PWP) model, and the K-profile parameterization (KPP) model, are examined in view of these results, and its implication on the model predictability is discussed.

scholarly journals Formation of a Diurnal Thermocline in the Ocean Mixed Layer Simulated by LES

2009 ◽  
Vol 39 (5) ◽  
pp. 1244-1257 ◽  
Author(s):  
Yign Noh ◽  
Gahyun Goh ◽  
Siegfried Raasch ◽  
Micha Gryschka
Keyword(s):  
Mixed Layer ◽  
Wave Breaking ◽  
Growth Stage ◽  
Langmuir Circulation ◽  
Ocean Mixed Layer ◽  
Eddy Simulation ◽  
Formation Stage ◽  
Large Eddy ◽  
Physical Variables ◽  
Shear Production

Abstract The formation of a diurnal thermocline in the ocean mixed layer under a stabilizing buoyancy flux was simulated successfully by large-eddy simulation, reproducing various features consistent with observation. The analysis of the simulation result revealed that the formation of a diurnal thermocline passes through two different phases: the formation of a thermocline (formation stage) and increasing thickness of the thermocline thereafter (growth stage). Turbulent kinetic energy (TKE) flux dominates TKE production within the mixed layer, but turbulence maintained by shear production at the thermocline causes stratification below the mixed layer. In addition, once the thermocline is formed, both the gradient and flux Richardson numbers maintain constant values at the thermocline. It was also found that a diurnal thermocline cannot be formed in the absence of both wave breaking and Langmuir circulation. Furthermore, the effects of stratification on turbulence were investigated based on the time series of various physical variables of turbulence at the diurnal thermocline and within the mixed layer, and the mechanism for diurnal thermocline formation is discussed.

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.

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
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