A dynamic eddy-viscosity closure model for large eddy simulations of two-dimensional decaying turbulence

2014 ◽  
Vol 28 (6-10) ◽  
pp. 363-382 ◽  
Author(s):  
O. San
Keyword(s):  
Eddy Viscosity ◽  
Large Eddy Simulations ◽  
Two Dimensional ◽  
Closure Model ◽  
Large Eddy ◽  
Decaying Turbulence

Evaluation of Turbulence Models Using Direct Numerical and Large-Eddy Simulation Data

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Hassan Raiesi ◽  
Ugo Piomelli ◽  
Andrew Pollard
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Eddy Viscosity ◽  
Predictive Accuracy ◽  
Turbulence Models ◽  
Special Treatment ◽  
Two Dimensional ◽  
Square Duct ◽  
Eddy Simulation ◽  
Large Eddy

The performance of some commonly used eddy-viscosity turbulence models has been evaluated using direct numerical simulation (DNS) and large-eddy simulation (LES) data. Two configurations have been tested, a two-dimensional boundary layer undergoing pressure-driven separation, and a square duct. The DNS and LES were used to assess the k−ε, ζ−f, k−ω, and Spalart–Allmaras models. For the two-dimensional separated boundary layer, anisotropic effects are not significant and the eddy-viscosity assumption works well. However, the near-wall treatment used in k−ε models was found to have a critical effect on the predictive accuracy of the model (and, in particular, of separation and reattachment points). None of the wall treatments tested resulted in accurate prediction of the flow field. Better results were obtained with models that do not require special treatment in the inner layer (ζ−f, k−ω, and Spalart–Allmaras models). For the square duct calculation, only a nonlinear constitutive relation was found to be able to capture the secondary flow, giving results in agreement with the data. Linear models had significant error.

scholarly journals Quasi-periodic forces and conditionally averaged characteristics of unsteady cavitation flow around a hydrofoil

2021 ◽  
Vol 2119 (1) ◽  
pp. 012030
Author(s):  
E I Ivashchenko ◽  
M Yu Hrebtov ◽  
R I Mullyadzhanov
Keyword(s):  
Reynolds Number ◽  
Liquid Phase ◽  
High Reynolds Number ◽  
Velocity Fields ◽  
Large Eddy Simulations ◽  
Two Dimensional ◽  
Cavitation Flow ◽  
Large Eddy ◽  
High Reynolds ◽  
Conditional Averaging

Abstract Large-eddy simulations are performed to investigate the cavitating flow around two dimensional hydrofoil section with angle of attack of 9° and high Reynolds number of 1.3×106. We use the Schnerr-Sauer model for accurate phase transitions modelling. Instantaneous velocity fields are compared successfully with PIV data using the methodology of conditional averaging to take into account only the liquid phase characteristics as in PIV. The presence of two frequencies in a spectrum corresponding to the full and partial cavity detachments is analysed.

On the implicit large eddy simulations of homogeneous decaying turbulence

2007 ◽  
Vol 226 (2) ◽  
pp. 1902-1929 ◽  
Author(s):  
Ben Thornber ◽  
Andrew Mosedale ◽  
Dimitris Drikakis
Keyword(s):  
Large Eddy Simulations ◽  
Large Eddy ◽  
Decaying Turbulence

Analysis and modelling of subgrid-scale motions in near-wall turbulence

1998 ◽  
Vol 356 ◽  
pp. 327-352 ◽  
Author(s):  
CARLOS HÄRTEL ◽  
LEONHARD KLEISER
Keyword(s):  
Eddy Viscosity ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Large Eddy Simulations ◽  
Inverse Cascade ◽  
Large Eddy ◽  
Wall Flow ◽  
Definition Of ◽  
Subgrid Stress ◽  
Near Wall

A numerical study of turbulent channel flow at various Reynolds numbers (Reτ=115, 210, 300) is conducted in order to examine the requirements for a reliable subgrid modelling in large-eddy simulations of wall-bounded flows. Using direct numerical simulation data, the interactions between large and small scales in the near-wall flow are analysed in detail which sheds light on the origin of the inverse cascade of turbulent kinetic energy observed in the buffer layer. It is shown that the correlation of the wall-normal subgrid stress and the wall-normal derivative of the streamwise grid-scale velocity plays the key role in the occurrence of the inverse cascade. A brief a priori test of several subgrid models shows that currently applied models are not capable of accounting properly for the complex interactions in the near-wall flow. A series of large-eddy simulations gives evidence that this deficiency may cause significant errors in important global quantities of the flow such as the mean wall shear stress. A study of the eddy-viscosity ansatz is conducted which reveals that the characteristic scales usually employed for the definition of the eddy viscosity are inappropriate in the vicinity of a wall. Therefore, a novel definition of the eddy viscosity is derived from the analysis of the near-wall energy budget. This new definition, which employs the wall-normal subgrid stress as a characteristic scale, is more consistent with the near-wall physics. No significant Reynolds-number effects are encountered in the present analysis which suggests that the findings may be generalized to flows at higher Reynolds numbers.

scholarly journals The Role of Wave-Induced Coriolis–Stokes Forcing on the Wind-Driven Mixed Layer

2005 ◽  
Vol 35 (4) ◽  
pp. 444-457 ◽  
Author(s):  
Jeff A. Polton ◽  
David M. Lewis ◽  
Stephen E. Belcher
Keyword(s):  
Analytical Solution ◽  
Observational Data ◽  
Mixed Layer ◽  
Analytical Solutions ◽  
Eddy Viscosity ◽  
Large Eddy Simulations ◽  
Current Profile ◽  
Large Eddy ◽  
The Mean ◽  
Mean Current

Abstract The interaction between the Coriolis force and the Stokes drift associated with ocean surface waves leads to a vertical transport of momentum, which can be expressed as a force on the mean momentum equation in the direction along wave crests. How this Coriolis–Stokes forcing affects the mean current profile in a wind-driven mixed layer is investigated using simple models, results from large-eddy simulations, and observational data. The effects of the Coriolis–Stokes forcing on the mean current profile are examined by reappraising analytical solutions to the Ekman model that include the Coriolis–Stokes forcing. Turbulent momentum transfer is modeled using an eddy-viscosity model, first with a constant viscosity and second with a linearly varying eddy viscosity. Although the Coriolis–Stokes forcing penetrates only a small fraction of the depth of the wind-driven layer for parameter values typical of the ocean, the analytical solutions show how the current profile is substantially changed through the whole depth of the wind-driven layer. It is shown how, for this oceanic regime, the Coriolis–Stokes forcing supports a fraction of the applied wind stress, changing the boundary condition on the wind-driven component of the flow and hence changing the current profile through all depths. The analytical solution with the linearly varying eddy viscosity is shown to reproduce reasonably well the effects of the Coriolis–Stokes forcing on the current profile computed from large-eddy simulations, which resolve the three-dimensional overturning motions associated with the turbulent Langmuir circulations in the wind-driven layer. Last, the analytical solution with the Coriolis–Stokes forcing is shown to agree reasonably well with current profiles from previously published observational data and certainly agrees better than the standard Ekman model. This finding provides evidence that the Coriolis–Stokes forcing is an important mechanism in controlling the dynamics of the upper ocean.

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