scholarly journals On the Convergence and Capability of the Large-Eddy Simulation of Concentration Fluctuations in Passive Plumes for a Neutral Boundary Layer at Infinite Reynolds Number

2020 ◽  
Vol 176 (3) ◽  
pp. 291-327 ◽  
Author(s):  
Hamidreza Ardeshiri ◽  
Massimo Cassiani ◽  
Soon Young Park ◽  
Andreas Stohl ◽  
Ignacio Pisso ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Concentration Fluctuations ◽  
Eddy Simulation ◽  
Neutral Boundary Layer ◽  
Large Eddy

Subgrid-scale modelling for the large-eddy simulation of high-Reynolds-number boundary layers

1997 ◽  
Vol 336 ◽  
pp. 151-182 ◽  
Author(s):  
BRANKO KOSOVIĆ
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Nonlinear Model ◽  
High Reynolds Number ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

It has been recognized that the subgrid-scale (SGS) parameterization represents a critical component of a successful large-eddy simulation (LES). Commonly used linear SGS models produce erroneous mean velocity profiles in LES of high-Reynolds-number boundary layer flows. Although recently proposed approaches to solving this problem have resulted in significant improvements, questions about the true nature of the SGS problem in shear-driven high-Reynolds-number flows remain open.We argue that the SGS models must capture inertial transfer effects including backscatter of energy as well as its redistribution among the normal SGS stress components. These effects are the consequence of nonlinear interactions and anisotropy. In our modelling procedure we adopt a phenomenological approach whereby the SGS stresses are related to the resolved velocity gradients. We show that since the SGS stress tensor is not frame indifferent a more general nonlinear model can be applied to the SGS parameterization. We develop a nonlinear SGS model capable of reproducing the effects of SGS anisotropy characteristic for shear-driven boundary layers. The results obtained using the nonlinear model for the LES of a neutral shear-driven atmospheric boundary layer show a significant improvement in prediction of the non-dimensional shear and low-order statistics compared to the linear Smagorinsky-type models. These results also demonstrate a profound effect of the SGS model on the flow structures.

scholarly journals A study of the wind turbine wake dynamics in the neutral boundary layer using large eddy simulation

2019 ◽  
Vol 32 ◽  
pp. 775-785
Author(s):  
Mohamed Marouan Ichenial ◽  
Abdellah Elhajjaji
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Eddy Simulation ◽  
Neutral Boundary Layer ◽  
Large Eddy ◽  
Turbine Wake ◽  
Wind Turbine Wake

The onset of dynamic stall at a high, transitional Reynolds number

2018 ◽  
Vol 861 ◽  
pp. 860-885 ◽  
Author(s):  
S. I. Benton ◽  
M. R. Visbal
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Separation Bubble ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Turbulent Shear ◽  
Eddy Simulation ◽  
Turbulent Separation ◽  
Large Eddy

Dynamic stall due to a ramp-type pitching motion is investigated on the NACA 0012 airfoil at chord Reynolds number of $Re_{c}=1.0\times 10^{6}$ through the use of wall-resolved large-eddy simulation. Emphasis is placed on the unsteady boundary-layer interactions that develop as the airfoil approaches stall. At this Reynolds number it is shown that turbulent separation moves upstream across much of the airfoil suction surface. When turbulent separation reaches the leading-edge separation bubble, a bursting event is initiated leading to a strong coherent leading-edge vortex structure. This vortex wraps up the turbulent shear layer to form a large dynamic stall vortex. The use of large-eddy simulation elucidates the roll of the laminar separation bubble in defining the onset of the dynamic stall process. Comparisons are made to identical simulations at lower Reynolds numbers of $Re_{c}=0.2\times 10^{6}$ and $0.5\times 10^{6}$. This comparison demonstrates trends in the boundary-layer mechanics that explain the sensitivity of the dynamic stall process to Reynolds number.

Large-Eddy Simulation Investigation of Impact of Roughness on Flow in a Low-Pressure Turbine

2016 ◽  
Author(s):  
Jongwook Joo ◽  
Gorazd Medic ◽  
Om Sharma
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Roughness Model ◽  
Roughness Elements ◽  
Large Eddy

Surface roughness can make boundary-layers separate in diffusing flow. Most roughness Reynolds Averaged Navier Stokes (RANS) models which change the boundary conditions to model the roughness effects cannot predict this phenomenon. In this study, Large-Eddy Simulation (LES) is performed to predict the roughness induced separation and investigate the flow physics to improve our understanding of the underlying phenomena. Flow over a roughened low-pressure turbine airfoil was simulated by LES with WALE subgrid-scale model [15]. The roughness is modeled as regularly placed roughness elements with a similar equivalent roughness height following Schlichting [1]. The roughness elements are gridded in a body-fitted and multi-block structured way. Over a range of Reynolds number, the LES correctly predicted the behavior — with the flow separation occurring only at the high Reynolds number. Analysis revealed that surface drag and boundary layer thickness increase as Reynolds number increases, which is opposite to the conventional smooth wall boundary-layer behavior. In the end, the thickened boundary layer undergoes separation in the diffusing section. RANS simulations are also conducted with a roughness model — over a smooth airfoil grid — and without a roughness model — by using the same rough airfoil grid. In all cases, no separation was observed. The boundary layer thickness predicted with RANS is thinner than those of LES, suggesting that models that only modify surface stress at the boundary do not properly capture the flow physics over the rough surface of an airfoil.

Subfilter-scale enrichment of planetary boundary layer large eddy simulation using discrete Fourier–Gabor modes

2017 ◽  
Vol 819 ◽  
pp. 494-539 ◽  
Author(s):  
Aditya S. Ghate ◽  
Sanjiva K. Lele
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
High Resolution ◽  
Large Eddy Simulation ◽  
Planetary Boundary Layer ◽  
Multiscale Simulation ◽  
Space Time ◽  
Computationally Efficient ◽  
Eddy Simulation ◽  
Large Eddy

A new multiscale simulation methodology is introduced to facilitate computationally efficient simulations of high Reynolds number turbulence seen in wall-bounded flows. The scale splitting methodology uses traditional large eddy simulation (LES) with a wall model to simulate the larger scales which are subsequently enriched using a space–time compatible kinematic simulation. Computational feasibility and robustness of the methodology are investigated using two idealized problems that emulate turbulence within the planetary boundary layer (PBL), and a finite Reynolds number channel flow problem which serves to validate the methodology against direct numerical simulation. The space–time correlations and spectra generated using enriched LES show excellent agreement with LES conducted at high resolution for all three problems; thereby demonstrating the potential of this approach for high resolution PBL simulations with a drastic reduction in the computational costs when compared to the conventional approach.

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