Effects of Parallel Processing on Large Eddy Simulations in ANSYS Fluent

2016 ◽  
Author(s):  
Puxuan Li ◽  
Steve J. Eckels ◽  
Ning Zhang ◽  
Garrett W. Mann
Keyword(s):  
Parallel Processing ◽  
Data Transfer ◽  
Turbulence Models ◽  
Large Eddy Simulations ◽  
Grid Turbulence ◽  
Ansys Fluent ◽  
Square Duct ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Large Eddy

Parallel processing is an effective computation in which many calculations are carried out simultaneously. In this paper, effects of shared-memory parallel processing on Large Eddy Simulations (LES) in ANSYS Fluent are presented. Fluent provides parallel processing to improve the speed of running programs. LES is one of the most popular viscosity models for turbulence used in computational fluid dynamics (CFD). Three kinds of LES with different sub-grid turbulence models were evaluated: Smagorinsky-Lilly Model (Lilly model), Wall-Adapting Local Eddy-viscosity Model (WALE model) and Wall Modeled Large Eddy Simulation (WMLES model). The running speed of the different models simulating a square duct on a single computer are compared. The relationship between wall-clock time and number of processors reveals the performances of different LES models. The part of the time that is not parallelizable such as file IO and data transfer is also considered based on Amdahl’s law.

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 Large Eddy Simulation of gravity currents with a high order DG method

2017 ◽  
Vol 8 (1) ◽  
pp. 128-148 ◽  
Author(s):  
Caterina Bassi ◽  
Antonella Abbà ◽  
Luca Bonaventura ◽  
Lorenzo Valdettaro
Keyword(s):  
Numerical Simulations ◽  
Gravity Current ◽  
Turbulence Models ◽  
Variable Density ◽  
Large Eddy Simulations ◽  
Benchmark Problems ◽  
Smagorinsky Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Dg Method

Abstract This work deals with Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of a turbulent gravity current in a gas, performed by means of a Discontinuous Galerkin (DG) Finite Elements method employing, in the LES case, LES-DG turbulence models previously introduced by the authors. Numerical simulations of non-Boussinesq lock-exchange benchmark problems show that, in the DNS case, the proposed method allows to correctly reproduce relevant features of variable density gas ows with gravity. Moreover, the LES results highlight, also in this context, the excessively high dissipation of the Smagorinsky model with respect to the Germano dynamic procedure.

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

Large Eddy Simulations of a Hydrocyclone

2002 ◽  
Author(s):  
Francisco Jose´ de Souza ◽  
Aristeu Silveira Neto
Keyword(s):  
Turbulence Models ◽  
Fluid Flows ◽  
Scale Model ◽  
Staggered Grid ◽  
Subgrid Scale ◽  
Step Method ◽  
Fractional Step Method ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subgrid Scale Modeling

Subgrid-scale modeling, which characterizes Large Eddy Simulation (LES), has been used to predict the behavior of a water-fed hydrocyclone operating without an air core. The governing equations were solved by a fractional step method on a staggered grid. The Smagorinsky subgrid-scale model was employed to account for turbulent effects. Numerical results actually capture the main features of the flow pattern and agree reasonably well with experiments, suggesting that LES represents an interesting alternative to classical turbulence models when applied to the numerical solution of fluid flows within hydrocyclones.

Large-Eddy Simulation of Roughened NACA65 Compressor Cascade

2017 ◽  
Author(s):  
Jongwook Joo ◽  
Gorazd Medic ◽  
Om Sharma
Keyword(s):  
Surface Roughness ◽  
Large Eddy Simulations ◽  
Surface Imaging ◽  
Potential Solution ◽  
Discrete Elements ◽  
Compressor Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Modeling ◽  
The One

Large eddy simulations over a NACA65 compressor cascade with roughness were performed for multiple roughness heights. The experiments show flow separation as airfoil roughness is increased. In LES computations, surface roughness was represented by regularly arranged discrete elements using guidelines from Schlichting. Results from wall-resolved LES indicate that specifying an equivalent sandgrain roughness height larger than the one in experiments is required to reproduce the same effects observed in experiments. This highlights the persisting uncertainty with matching the experimental roughness geometry in LES computations, pointing towards surface imaging and digitization as a potential solution. Some initial analysis of flow physics has been conducted with the aim of guiding the RANS modeling for roughness.

scholarly journals Dynamic LES of the magnetohydrodynamic flow in a square duct with the varied wall conductance parameters

2021 ◽  
Vol 2116 (1) ◽  
pp. 012036
Author(s):  
A Blishchik ◽  
S Kenjereš
Keyword(s):  
Electrical Conductivity ◽  
Turbulent Flow ◽  
Magnetohydrodynamic Flow ◽  
Large Eddy Simulations ◽  
Scale Model ◽  
Turbulent Structures ◽  
Square Duct ◽  
Large Eddy ◽  
Side Walls

Abstract The current study is focused on the magnetohydrodynamics and demonstrates how electrical conductivity of the wall can affect the turbulent flow in the square duct. Different variations of the boundary walls have been considered including arbitrary conductive walls. The Large Eddy Simulations method with the dynamic Smagorinsky sub-grid scale model have been used for the turbulent structures resolving. Results show the significant impact of the wall conductance parameters for both Hartmann and side walls.

Large Eddy Simulation of the Heat Transfer Due to Swirling and Non-Swirling Jet Impingement

2008 ◽  
Author(s):  
Naseem Uddin ◽  
S. O. Neumann ◽  
B. Weigand
Keyword(s):  
Heat Transfer ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Test Case ◽  
Complex Flow ◽  
Free Jet ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Target Wall

Turbulent impinging jet is a complex flow phenomenon involving free jet, impingement and subsequent wall jet development zones; this makes it a difficult test case for the evaluation of new turbulence models. The complexity of the jet impingement can be further amplified by the addition of the swirl. In this paper, results of Large Eddy Simulations (LES) of swirling and non-swirling impinging jet are presented. The Reynolds number of the jet based on bulk axial velocity is 23000 and target-to-wall distance (H/D) is two. The Swirl numbers (S) of the jet are 0,0.2, 0.47. In swirling jets, the heat transfer at the geometric stagnation zone deteriorates due to the formation of conical recirculation zone. It is found numerically that the addition of swirl does not give any improvement for the over all heat transfer at the target wall. The LES predictions are validated by available experimental data.

scholarly journals Prediction of flow and dispersion in cross–ventilated buildings

2019 ◽  
Vol 128 ◽  
pp. 05002
Author(s):  
Ali Cemal Benim ◽  
Michael Diederich ◽  
Ali Nahavandi
Keyword(s):  
Computational Analysis ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Turbulence Structure ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Grid Independence

The present paper presents a detailed computational analysis of flow and dispersion in a generic isolated single–zone buildings. First, a grid generation strategy is discussed, that is inspired by a previous computational analysis and a grid independence study. Different turbulence models are appliedincluding two-equation turbulence models, the differential Reynolds Stress Model, Detached Eddy Simulation and Zonal Large Eddy Simulation. The mean velocity and concentration fields are calculated and compared with the measurements. A satisfactory agreement with the experiments is not observed by any of the modelling approaches, indicating the highly demanding flow and turbulence structure of the problem.

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