Statistical Analysis of Dynamic Subgrid Modeling Approaches in Large Eddy Simulation

Hossen, Mohammad Khalid; Variyath, Asokan Mulayath; Alam, Jahrul M

doi:10.20944/preprints202109.0438.v1

Cited by 8 publications

(9 citation statements)

References 35 publications

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“…is found to be well correlated with the energy flux < 𝜏 𝑖𝑗 𝑆 𝑖𝑗 >; Fig. 1 supports the theoretical interpretation regarding the energy flux and viscous dissipation [8]. Indeed, the energy is transferred by large eddies to the subgrid-scale, which is dissipated at a rate of subgrid-scale dissipation, 𝜀 𝑠𝑔𝑠 = 2𝜗 𝜏 ||𝑆||.…”

Section: Validation Strategiessupporting

confidence: 81%

“…Finally, the second invariant rotation rate is getting by, The JPDF map between the second invariant (𝑄 𝐺 ) and third invariant (𝑅 𝐺 ), and topological classification of local flow fields are shown in Fig. 2, see more detailed information [8], [15], [16]. The region of Fig.…”

Section: Joint Probability Density Function (Jpdf) Of Sgs Modelsmentioning

confidence: 99%

“…They considered the Karman-Harwoth equation [5] and the interpretation that the energy flux from large to small scale would balance the viscous dissipation. Indeed, these findings lead to creating an option for more studies on how vortex stretching reduces dissipation while at the same time acting for the down-scale cascade of energy (e.g., see [4], [8]).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Study of Large-eddy Simulation using Statistical and Machine Learning Techniques

Hossen

2022

J. eng. adv.

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The numerical solution of Navier-Stokes (N-S) equations has been found useful in various disciplines during its development, especially in recent years. However, a large-eddy simulation method has been developed to model the subgrid-scale dissipation rate by closing the Navier-Stokes equations. Because the instantaneous and time-averaged statistic characteristics of the subgrid-scale turbulent kinetic energy and dissipation have been studied by large eddy simulation. The purpose of this study is to check the statistical and machine learning of the subgrid-scale energy dissipation. As we know that the current turbulence theory states that the vortex stretching mechanism transports energy from large to small scales and leads to a high energy dissipation rate in a turbulent flow. Hence, a vortex-stretching-based subgrid-scale model is considered regarding the square of the velocity gradient to detect the playing role of the vortex stretching mechanism. The study in this article has shown a two-step process. Considering a posteriori statistic of the velocity gradient is analyzed through higher-order statistics and joint probability density function. Secondly, a machine learning approach is studied on the same data. The results of the vortex-stretching-based subgrid-scale model are then compared with the other two dynamic subgrid models, such as the localized dynamic kinetic energy equation model and the TKE-based Deardorff model. The results suggest that the vortex-stretching-based model can detect the significant subgrid-scale dissipation of small-scale motions and predict satisfactory turbulence statistics of the velocity gradient tensor.

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Section: Validation Strategiessupporting

confidence: 81%

Section: Joint Probability Density Function (Jpdf) Of Sgs Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Study of Large-eddy Simulation using Statistical and Machine Learning Techniques

Hossen

2022

J. eng. adv.

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“…This is equivalent to mimicking the effects of dynamical variations of C s (x, t) via the stretching of vortices. Based on LES of decaying homogeneous isotropic turbulence for Reynolds numbers up to 10 8 (using the localized dynamic Smagorinsky model [34]), we found that c k = 0.325 ± 0.035. Thus, a fixed value of c k = 0.325 is considered in this article.…”

Section: Vortex-stretching Based Scale-adaptive Subgrid Modelmentioning

confidence: 93%

“…Note that the subgrid model Eq (9) implicitly adapts the energy flux as the characteristic length scale of turbulence dissipation varies locally. Recent work of [34,15,35] evaluated the scaleadaptive LES model, Eq (9), in the case of isotropic turbulence, and atmospheric boundary layer flow over urban and hilly terrain. In this research, we consider an improved actuator disk model and show that our scale-adaptive LES method adequately captures the near turbine dynamics.…”

Section: Vortex-stretching Based Scale-adaptive Subgrid Modelmentioning

confidence: 99%

Vortex-Stretching based Large Eddy Simulation Framework for Wind Farms

Singh¹,

Alam²

2022

Preprint

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In large wind farms, wake distribution behind a wind turbine causes a considerable reduction of wind velocity for downstream wind turbines, resulting in a significant amount of power loss. Therefore, it is very crucial to predict wind turbine wakes efficiently. Thus, we propose a large-eddy simulation (LES) methodology, which takes the vorticity stretching to model transients in wind turbine wakes. In addition, we present an improved actuator disk model, which accounts for two-way feedback between the atmosphere and the wakes. First, we show that the vertical profile of the mean wind predicted with the new model has an excellent agreement with experimental measurements. Next, we validate the predicted Reynolds stresses against wind tunnel data and show that the dispersive stresses account for about 40% of Reynolds stresses. Finally, we show that the proposed LES method accurately predicts the characteristics of wind turbine wakes. Comparing the LES results with previously reported data, we have found that the new LES framework accurately predicts the flow statistics in both the near-wake and the far-wake regions.

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Influence of Ablation Deformation on Aero-Optical Effects in Hypersonic Vehicles

Yang

Liu

et al. 2023

Aerospace

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High-speed turbulence is generated when hypersonic vehicles fly in the atmosphere, which can create aero-optical effects and interfere with optical navigation and guidance systems. At the same time, the front end and optical window of hypersonic vehicles are exposed to an aerodynamic heating environment, leading to the head ablation and thermal deformation of the optical window. This further aggravates the turbulent transition process and makes the error of the aero-optical effects more difficult to predict. In this paper, the aero-optical effects under the condition of high-temperature ablation were analyzed. Ablation deformation models of both the head and optical window were established. Then, a high-speed flow field was simulated under different flight conditions. The distortion characteristics of the aero-optical effects were obtained through the photon transmission theory. The simulation results show that the ablation deformation of hypersonic vehicles under an aerodynamic heating environment aggravates the disturbance error of the aero-optical effects. Moreover, with the increase in the flight speed and the decrease in the flight altitude, the ablation deformation of the hypersonic vehicles and the aero-optical effects distortion both gradually increase. The research in this paper provides a reference for the prediction of aero-optical distortion in an aerothermal environment.

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Statistical Analysis of Dynamic Subgrid Modeling Approaches in Large Eddy Simulation

Cited by 8 publications

References 35 publications

A Study of Large-eddy Simulation using Statistical and Machine Learning Techniques

A Study of Large-eddy Simulation using Statistical and Machine Learning Techniques

Vortex-Stretching based Large Eddy Simulation Framework for Wind Farms

Influence of Ablation Deformation on Aero-Optical Effects in Hypersonic Vehicles

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