scholarly journals Vertical eddy diffusivity parameterization based on a large eddy simulation and its impact on prediction of hurricane landfall

2020 ◽  
Author(s):  
Xin Li ◽  
Zhaoxia Pu
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Diffusivity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Vertical Eddy Diffusivity ◽  
Vertical Eddy

Evaluation of the WRF PBL Parameterizations for Marine Boundary Layer Clouds: Cumulus and Stratocumulus

2013 ◽  
Vol 141 (7) ◽  
pp. 2265-2271 ◽  
Author(s):  
Hsin-Yuan Huang ◽  
Alex Hall ◽  
Joao Teixeira
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Marine Boundary Layer ◽  
Layer Structure ◽  
Model Performance ◽  
Simulation Models ◽  
Eddy Diffusivity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Boundary Layer Cloud

Abstract The performance of five boundary layer parameterizations in the Weather Research and Forecasting Model is examined for marine boundary layer cloud regions running in single-column mode. Most parameterizations show a poor agreement of the vertical boundary layer structure when compared with large-eddy simulation models. These comparisons against large-eddy simulation show that a parameterization based on the eddy-diffusivity/mass-flux approach provides a better performance. The results also illustrate the key role of boundary layer parameterizations in model performance.

Large Eddy Simulation of the Mixing of a Passive Scalar in a High-Schmidt Turbulent Jet

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Juan M. Mejía ◽  
Amsini Sadiki ◽  
Alejandro Molina ◽  
Farid Chejne ◽  
Pradeep Pantangi
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Diffusivity ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Water Stream ◽  
Eddy Simulation ◽  
Turbulent Schmidt Number ◽  
Large Eddy ◽  
Number Flow ◽  
Simulation Results

Accurate subgrid-scale (SGS) scalar flux models are essential when large eddy simulation (LES) is used to represent flow, mixing and transport of passive and active scalars in engineering, and environmental applications in turbulent regime. Many SGS scalar flux models have been developed for flows with low Schmidt numbers (Sc), but their application to high Sc flows has important limitations. In high Sc flows, the behavior of the scalar field becomes anisotropic because of intermittency effects, phenomenon that must be accounted for by SGS scalar flux models. The objective of this paper is to evaluate the ability of three SGS scalar flux models to predict the scalar behavior of a high Sc-number flow configuration, namely the anisotropy-resolved SGS scalar flux model: (1) appropriate for high Sc-number flow configurations, and two additional SGS models (linear eddy diffusivity based SGS models) with (2) constant, and (3) dynamically calculated turbulent Schmidt number. The LES simulation results accomplished by these models are compared to each other and to experimental data of a turbulent round jet discharging a diluted scalar into a low-velocity coflowing water stream. The comparison of simulation results and experimental observations shows that, in general, all SGS models reproduce the mean filtered concentration distribution in radial direction. The dynamic eddy diffusivity and anisotropy models reproduce the rms of the concentration and SGS scalar fluxes distribution. In particular, the anisotropy model improves the prediction reliability of LES. However, the three models evaluated in this study cannot accurately predict the scalar behavior at the superviscous layer. Finally, this work demonstrates that complex models can achieve reliable predictions on reasonable grids using less computational effort, while simple models require fine grids with increased computational costs.

Scale-Similarity Subgrid-Scale Turbulence Closure for Supercell Simulations at Kilometer-Scale Resolutions: Comparison Against a Large Eddy Simulation

2020 ◽  
Author(s):  
Shiwei Sun ◽  
Bowen Zhou ◽  
Ming Xue ◽  
Kefeng Zhu
Keyword(s):  
Large Eddy Simulation ◽  
Deep Convection ◽  
Eddy Diffusivity ◽  
Turbulent Fluxes ◽  
Subgrid Scale ◽  
Diffusion Type ◽  
Eddy Simulation ◽  
Gradient Diffusion ◽  
Large Eddy ◽  
Scale Similarity

AbstractIn numerical simulations of deep convection at kilometer-scale horizontal resolutions, in-cloud subgrid-scale (SGS) turbulence plays an important role in the transport of heat, moisture and other scalars. By coarse-graining a 50 m high-resolution large-eddy simulation (LES) of an idealized supercell storm to kilometer-scale grid spacings ranging from 250 m to 4 km, the SGS fluxes of heat, moisture, cloud and precipitating water contents are diagnosed a priori. The kilometer-scale simulations are shown to be within the “gray zone” as in-cloud SGS turbulent fluxes are comparable in magnitude to the resolved fluxes at 4 km spacing, and do not become negligible until ~500 m spacing. Vertical and horizontal SGS fluxes are of comparable magnitudes, both exhibit non-local characteristics associated with deep convection as opposed to local gradient-diffusion type of turbulent mixing. As such, they are poorly parameterized by eddy-diffusivity-based closures. To improve the SGS representation of turbulent fluxes in deep convective storms, a scale-similarity LES closure is adapted to kilometer-scale simulations. The model exhibits good correlations with LES-diagnosed SGS fluxes, and is capable of representing counter-gradient fluxes. In a posteriori tests, supercell storms simulated with the refined similarity closure model at kilometer-scale resolutions show better agreement with the LES benchmark in terms of SGS fluxes than those with a turbulent-kinetic-energy-based gradient-diffusion scheme. However, it underestimates the strength of updraft, which is suggested to be a consequence of the model effective resolution being lower than the native grid resolution.

Large eddy simulation of scalar turbulence using a new subgrid eddy diffusivity model

2007 ◽  
Vol 28 (2) ◽  
pp. 268-274 ◽  
Author(s):  
Yu Guo ◽  
Chun-Xiao Xu ◽  
Guixiang Cui ◽  
Zhaoshun Zhang ◽  
Liang Shao
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Diffusivity ◽  
Eddy Simulation ◽  
Scalar Turbulence ◽  
Large Eddy
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