An improved dynamic non-equilibrium wall-model for large eddy simulation

2014 ◽  
Vol 26 (1) ◽  
pp. 015108 ◽  
Author(s):  
George Ilhwan Park ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Wall Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Non Equilibrium

Large Eddy Simulation of Turbulent Flow Laden With Binary Mixture of Particles

2007 ◽  
Author(s):  
Neng-Tsung Chang ◽  
Chih-Hung Hsu ◽  
Keh-Chin Chang
Keyword(s):  
Binary Mixture ◽  
Large Eddy Simulation ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Wall Region ◽  
Wall Roughness ◽  
Wall Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Normal Particle

Particle-laden turbulent channel flow at Reτ = 644, loaded with binary mixture of particles, is numerically studied using the Lagrangian particle tracking method coupled with large eddy simulation. Turbulence statistics of different particle groups are analyzed. Two particle-wall models are applied to this study with / without considering wall roughness. Taking into considerations of rough wall model, the effect of wall roughness in the computations strengthens the wall-normal particle velocity fluctuations. As a result, particles tend to move from the near-wall region to the central core region. It leads to decrement of particle accumulation in the near-wall region as compared to the case considering the smooth wall model. The wall-normal particle mixing capability is enhanced which results in the redistribution of particles in the channel. The behavior of particle motion in the turbulent channel flow should be, thus, dependent on not only the value of Stokes number but also the wall roughness level.

scholarly journals A New Wall Model for Large Eddy Simulation of Separated Flows

Fluids ◽  
2019 ◽  
Vol 4 (4) ◽  
pp. 197 ◽  
Author(s):  
Ahmad Fakhari
Keyword(s):  
Large Eddy Simulation ◽  
Pressure Gradient ◽  
Separated Flows ◽  
Two Dimensional ◽  
Wall Model ◽  
Law Of The Wall ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Immersed Boundaries ◽  
Near Wall

The aim of this work is to propose a new wall model for separated flows which is combined with large eddy simulation (LES) of the flow field in the whole domain. The model is designed to give reasonably good results for engineering applications where the grid resolution is generally coarse. Since in practical applications a geometry can share body fitted and immersed boundaries, two different methodologies are introduced, one for body fitted grids, and one designed for immersed boundaries. The starting point of the models is the well known equilibrium stress model. The model for body fitted grid uses the dynamic evaluation of the von Kármán constant κ of Cabot and Moin (Flow, Turbulence and Combustion, 2000, 63, pp. 269–291) in a new fashion to modify the computation of shear velocity which is needed for evaluation of the wall shear stress and the near-wall velocity gradients based on the law of the wall to obtain strain rate tensors. The wall layer model for immersed boundaries is an extension of the work of Roman et al. (Physics of Fluids, 2009, 21, p. 101701) and uses a criteria based on the sign of the pressure gradient, instead of one based on the friction velocity at the projection point, to construct the velocity under an adverse pressure gradient and where the near-wall computational node is in the log region, in order to capture flow separation. The performance of the models is tested over two well-studied geometries, the isolated two-dimensional hill and the periodic two-dimensional hill, respectively. Sensitivity analysis of the models is also performed. Overall, the models are able to predict the first and second order statistics in a reasonable way, including the position and extension of the downward separation region.

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