scholarly journals Large eddy simulation (LES) of wind-driven circulation in a peri-alpine lake: Detection of turbulent structures and implications of a complex surrounding orography

2017 ◽  
Vol 122 (6) ◽  
pp. 4704-4722 ◽  
Author(s):  
Marco A. Santo ◽  
Marco Toffolon ◽  
Giulia Zanier ◽  
Lorenzo Giovannini ◽  
Vincenzo Armenio
Keyword(s):  
Large Eddy Simulation ◽  
Alpine Lake ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wind Driven Circulation

Turbulence and Vertical Fluxes in the Stable Atmospheric Boundary Layer. Part I: A Large-Eddy Simulation Study

2013 ◽  
Vol 70 (6) ◽  
pp. 1513-1527 ◽  
Author(s):  
Jing Huang ◽  
Elie Bou-Zeid
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Atmospheric Boundary Layer ◽  
Length Scale ◽  
Quasi Equilibrium ◽  
Turbulent Structures ◽  
Constant Length ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Stable Atmospheric Boundary Layer

Abstract This study seeks to quantitatively and qualitatively understand how stability affects transport in the continuously turbulent stably stratified atmospheric boundary layer, based on a suite of large-eddy simulations. The test cases are based on the one adopted by the Global Energy and Water Cycle Experiment (GEWEX) Atmospheric Boundary Layer Study (GABLS) project, but with a largely expanded stability range where the gradient Richardson number (Rig) reaches up to around 1. The analysis is mainly focused on understanding the modification of turbulent structures and dynamics with increasing stability in order to improve the modeling of the stable atmospheric boundary layer in weather and climate models, a topic addressed in Part II of this work. It is found that at quasi equilibrium, an increase in stability results in stronger vertical gradients of the mean temperature, a lowered low-level jet, a decrease in vertical momentum transport, an increase in vertical buoyancy flux, and a shallower boundary layer. Analysis of coherent turbulent structures using two-point autocorrelation reveals that the autocorrelation of the streamwise velocity is horizontally anisotropic while the autocorrelation of the vertical velocity is relatively isotropic in the horizontal plane and its integral length scale decreases as stability increases. The effects of stability on the overall turbulent kinetic energy (TKE) and its budget terms are also investigated, and it is shown that the authors' large-eddy simulation results are in good agreement with previous experimental findings across varied stabilities. Finally, Nieuwstadt's local-scaling theory is reexamined and it is concluded that the height z is not a relevant scaling parameter and should be replaced by a constant length scale away from the surface, indicating that the z-less range starts lower than previously assumed.

Large-eddy simulation evaluation of wind loads on a high-rise building based on the multiscale synthetic eddy method

2018 ◽  
Vol 22 (4) ◽  
pp. 997-1006 ◽  
Author(s):  
Yin Luo ◽  
Hongjun Liu ◽  
Huili Xue ◽  
Kun Lin
Keyword(s):  
Large Eddy Simulation ◽  
Wind Pressure ◽  
Turbulent Structures ◽  
Building Model ◽  
High Rise ◽  
High Rise Building ◽  
Eddy Simulation ◽  
Simulation Evaluation ◽  
Large Eddy ◽  
Inflow Turbulence

In this study, the multiscale synthetic eddy method, which can establish coherent turbulent structures and satisfy predefined turbulent statistical and spectral properties, is employed to generate the inflow turbulence for large-eddy simulation of a high-rise building. The recycling method of Lund and synthetic eddy method is also applied to assess the suitability of multiscale synthetic eddy method. The wind pressure at each mesh face centre on the surface of the high-rise building model is exported in the simulation to determine the wind-induced aerodynamic loads. Compared with the synthetic eddy method, the multiscale synthetic eddy method result is in higher agreement with that of the recycling method of Lund in terms of the wind pressure distribution, wind load characteristic and external flow field of the high-rise building.

scholarly journals Study of a Premixed Turbulent Counter-Flow Flame with a Large Eddy Simulation Method

2021 ◽  
Author(s):  
Y. Gong ◽  
W. P. Jones ◽  
A. J. Marquis
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Simulation Method ◽  
Turbulent Flames ◽  
Turbulent Structures ◽  
Counter Flow ◽  
Eddy Simulation ◽  
Predicted Probability ◽  
Large Eddy ◽  
Flame Region

AbstractThe turbulent counter-flow flame (TCF) has proven to be a useful benchmark to study turbulence-chemistry interactions, however, the widely observed bulk flow fluctuations and their influence on the flame stability remain unclear. In the present work, premixed TCFs are studied numerically using a Large Eddy Simulation (LES) method. A transported probability density function (pdf) approach is adopted to simulate the sub-grid scale (sgs) turbulence-chemistry interactions. A solution to the joint sgs-pdf evolution equation for each of the relative scalars is obtained by the stochastic fields method. The chemistry is represented using a simplified chemical reaction mechanism containing 15 reaction steps and 19 species. This work compares results with two meshing strategies, with the domain inside nozzles included and excluded respectively. A conditional statistical approach is applied to filter out the large scale motions of the flame. With the use of digital turbulence, the velocity field in the flame region is well reproduced. The processes of local extinction and re-ignition are successfully captured and analysed together with the strain rate field, and local extinctions are found correlated to the turbulent structures in the reactant stream. The predicted probability of localised extinction is in good agreement with the measurements, and the influence of flame stoichiometry are also successfully reproduced. Overall, the current results serve to demonstrate the capability of the LES-pdf method in the study of the premixed opposed jet turbulent flames.

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