Review
Mechanics
Robert D. Moser, Sigfried W. Haering, Gopal R. Yalla
Summary: This review focuses on the a priori statistical characteristics of large eddy simulation (LES) models, highlighting the importance of other subgrid statistical characteristics in complex turbulent flows and the consistency of these characteristics in models. The assessment of known statistical characteristics of subgrid models is aimed at aiding the ongoing development of LES models.
ANNUAL REVIEW OF FLUID MECHANICS, VOL 53
(2021)
Article
Engineering, Aerospace
Mohammad Khalid Hossen, Asokan Mulayath Variyath, Jahrul M. Alam
Summary: This study investigates the statistical characteristics of vortex stretching in Large Eddy Simulation (LES) and finds that the stretching rate provides the necessary energy dissipation rate for modeling subgrid-scale turbulence. By comparing the interaction of subgrid stresses with filtered quantities, it is revealed that the stretching mechanism extracts energy from large-scale motion and transfers it to small-scale stretched vortices.
Article
Computer Science, Interdisciplinary Applications
A. C. W. Creech, A. Jackson
Summary: This paper introduces a hybrid approach for explicitly-filtered Large Eddy Simulation using a Discontinous Galerkin discretisation for velocity, which incorporates information from a Continuous Galerkin version of the velocity field to improve computational performance while maintaining stability and accuracy.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Mechanics
Han Qi, Xinliang Li, Changping Yu
Summary: This paper introduces a new one-equation eddy-viscosity model based on SGS helicity for LES of turbulent flows. The model is tested and validated in homogeneous and isotropic helical turbulence simulations, showing improved accuracy in predicting energy and helicity spectra. The model also accurately predicts mean velocity, turbulent stress, and viscous shear stress in channel flow LES, providing more flow structures compared to traditional SGS models.
Article
Mechanics
R. Vicente Cruz, E. Lamballais
Summary: The development of implicit approaches has sparked a debate on the usefulness of explicit subgrid-scale modelling in large-eddy simulation. Two generic turbulent flows, the Taylor-Green vortex problem and pipe flow, were considered to compare implicit modelling and the popular Smagorinsky model. The results showed that implicit modelling outperforms the Smagorinsky model. The study also revisited the concept of spectral eddy viscosity and found that implicit modelling exhibits an anisotropic nature that is consistent with the computational mesh, while the Smagorinsky model is sensitive to numerical errors. Moreover, the potential of implicit large-eddy simulation for accurately computing near-wall turbulence in a pipe flow was demonstrated. Overall, the article highlights the advantages and limitations of various subgrid-scale modelling approaches in large-eddy simulation and suggests directions for future research. Rating: 8/10.
JOURNAL OF TURBULENCE
(2023)
Article
Thermodynamics
Fatiha Nmira, Jean-Louis Consalvi
Summary: The present study aims to quantify individual contributions to turbulence-radiation interaction in large methanol pool fires and provide guidance for the development of simplified models. The study finds that temperature self-correlation and absorption coefficient-temperature cross correlation are the main contributors to both resolved-scale and subgrid-scale emission TRI. The contribution of subgrid-scale absorption coefficient self-correlation becomes negligible as the pool size increases.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Zhideng Zhou, Xiang I. A. Yang, Fengshun Zhang, Xiaolei Yang
Summary: In this study, a wall model is developed using the wall-resolved large-eddy simulation (WRLES) data of flow over periodic hills (PH) and the law of the wall (LoW) for data-driven wall-modeled large-eddy simulations of various wall-bounded turbulent flows. A feedforward neural network (FNN) is employed to construct the model. The performance of the obtained FNN_PH-LoW model is successfully evaluated using the direct numerical simulation data of turbulent channel flows and the WRLES data of PH cases, and it is applied to turbulent channel flows with a wide range of Reynolds numbers.
Article
Mechanics
Ken-ichi Abe
Summary: This study investigates the effect of filter width definition on the prediction accuracy of a subgrid scale (SGS) model in Large Eddy Simulation (LES). It is found that using the cube root of grid-cell volume as the filter width may not always be appropriate, and the influence of a grid width in one direction much smaller than in other directions should be excluded when determining the filter width for proper evaluation of an SGS model.
Article
Meteorology & Atmospheric Sciences
Yu Cheng, Marco G. Giometto, Pit Kauffmann, Ling Lin, Chen Cao, Cody Zupnick, Harold Li, Qi Li, Yu Huang, Ryan Abernathey, Pierre Gentine
Summary: In large-eddy simulations, subgrid-scale processes are parameterized as a function of filtered grid-scale variables. This paper applies supervised deep neural networks (DNNs) to learn subgrid stresses and achieves higher correlation compared to traditional models, with applicability to different resolutions and stability conditions.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Thermodynamics
Jian Teng, Zelong Yuan, Jianchun Wang
Summary: Based on the framework of deconvolutional artificial neural network (DANN), this study extends the DANN approach to model subgrid-scale (SGS) terms in chemically reacting compressible turbulent flow. The DANN method outperforms traditional methods in terms of modeling performance and can predict flow variables accurately using limited training samples.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Meteorology & Atmospheric Sciences
Shiwei Sun, Bowen Zhou, Ming Xue, Kefeng Zhu
Summary: In numerical simulations of deep convection at kilometer-scale horizontal resolutions, it is shown that in-cloud subgrid-scale turbulence plays a vital role in the transport of heat, moisture, and other scalars. By adapting a scale-similarity LES closure to kilometer-scale simulations, improvements are made in representing turbulent fluxes in deep convective storms.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2021)
Article
Engineering, Marine
D. A. Lysenko, I. S. Ertesvag
Summary: The study utilized large-eddy simulation to analyze the turbulent separated flow over an equilateral triangular cylinder at a Reynolds number of 45000, utilizing various algebraic subgrid scale closures and comparing numerical simulations with experimental data to investigate the effects of blockage on flow characteristics.
Article
Mechanics
Xander M. de Wit, Adrian van Kan, Alexandros Alexakis
Summary: In this study, direct numerical simulations of thin-layer flow were used to investigate whether the bistable range survives as the domain size and turbulence intensity are increased. The research found that the bistable range grows as the box size and/or Reynolds number Re are increased.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Mechanical
Zelong Yuan, Yunpeng Wang, Chenyue Xie, Jianchun Wang
Summary: This paper proposes a new dynamic nonlinear algebraic model for subgrid-scale (SGS) stress in large-eddy simulation. The model adaptively calculates the coefficients through scale-similarity relation, resulting in considerably better predictions compared to conventional models. The model accurately predicts turbulent statistics and spatial structures in reasonable agreement with filtered DNS data.
ADVANCES IN AERODYNAMICS
(2022)
Article
Mechanics
Masahide Inagaki
Summary: In this study, a mixed SGS model is applied to predict the behavior of non-Newtonian fluids, successfully avoiding the dependency on grid resolution seen in traditional SGS models. As the power law index n decreases, the model can capture the anisotropy of turbulence stress and quantitatively predict the reduction of wall-friction drag.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2021)
Article
Thermodynamics
Amin Rasam, Stefan Wallin, Geert Brethouwer, Arne V. Johansson
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2017)
Article
Meteorology & Atmospheric Sciences
Velibor Zeli, Geert Brethouwer, Stefan Wallin, Arne V. Johansson
BOUNDARY-LAYER METEOROLOGY
(2019)
Article
Meteorology & Atmospheric Sciences
Velibor Zeli, Geert Brethouwer, Stefan Wallin, Arne Johansson
BOUNDARY-LAYER METEOROLOGY
(2020)
Article
Meteorology & Atmospheric Sciences
Velibor Zeli, Geert Brethouwer, Stefan Wallin, Arne V. Johansson
Summary: This study demonstrates that the explicit algebraic Reynolds-stress (EARS) model, when implemented in a single-column context, is able to accurately capture the main features of both stable and dry convective atmospheric boundary layers (ABL). By comparing results with large-eddy simulations, it is shown that the EARS model performs well and provides valuable insights into the counter-gradient heat flux in the upper part of the ABL. The study concludes that the EARS model, with the same formulation and calibration, can be applied to a wide range of stable and moderately unstable stratifications.
BOUNDARY-LAYER METEOROLOGY
(2021)
Article
Thermodynamics
Ali Mohammad Ranjbar, Zeinab Pouransari, Majid Siavashi
Summary: This study investigated the turbulent forced convection heat transfer of air in the presence of porous pin fins for cooling thermal parts of devices. Five fin structures, two different fin arrangements, and three various Darcy numbers were examined to analyze the effects of these parameters on the heat sink performance. It was concluded that the decreasing-aligned pin fin configuration with the highest Darcy number provided the best performance among the studied cases.
APPLIED THERMAL ENGINEERING
(2021)
Article
Chemistry, Multidisciplinary
Hasti Makhdoum, Zeinab Pouransari
Summary: This study focuses on analyzing the oil and natural gas reserves of Iran, which play a crucial role in the global energy market. The Hubbert peak theory is used to analyze and predict the production rates of these nonrenewable reserves. The study also compares Iran's reserves with other key countries and examines the impact of local consumption and international sanctions on Iran's production. In addition, global energy policies and the future outlook for Iran's oil and natural gas production are discussed.
Article
Thermodynamics
Mahyar Seyd Eshaghi, Mohammad Ameri, Amin Rasam, Mokhtar Bidi
Summary: In this study, numerical simulations are employed to analyze the hydrodynamic and thermal entrance regions of turbulent flow in a circular tube with a tight-fit twisted tape insert and prescribed constant wall temperature. Ethylene glycol, water, and Therminol-LT are considered, with inlet velocities ranging from 0.4 to 1 m/s and three common pitch ratios of 5, 8, and 10. The simulations utilize the RANS equations with the Boussinesq hypothesis and the SST-K-Omega turbulence model. Mean non-dimensional velocity and temperature profiles are assessed to confirm the flow's full development. Distinguishing features of the developing and fully-developed regions are compared using velocity and temperature profiles, contours, and flow streamlines. This analysis provides a novel guideline for assessing flow development in pipe flows with twisted-tape inserts. Correlations for dimensionless hydrodynamic and thermal entrance lengths, as well as Nu and Fanning friction factor, are proposed for the first time, allowing for the estimation of these quantities under a wide range of operating conditions.
THERMAL SCIENCE AND ENGINEERING PROGRESS
(2023)
Article
Mechanics
Zeinab Pouransari, Amin Rasam
Summary: An extension of the explicit algebraic subgrid-scale (SGS) stress model (EASSM) is proposed to account for the non-local equilibrium between the production, P, and viscous dissipation, e, of the SGS turbulent kinetic energy. The new derivation extracts a cubic algebraic equation for P/e from the modeled transport equation for the SGS stress anisotropy, improving the EASSM predictions with less computational costs. The performance assessment shows that the enhanced EASSM formulation reduces resolution dependence and improves predictions at low resolutions, affecting various turbulence statistics of interest.
Article
Mechanics
Zeinab Pouransari
Summary: This study investigates the statistical properties of small-scale scalar fluctuations in wall-bounded turbulent flows. The presence of a magnetic field leads to statistical anisotropy, even at small-scale gradient fields. Furthermore, an increase in scalar dissipation rates decreases the mixing timescale, potentially enhancing overall mixing.
Article
Energy & Fuels
Zeinab Pouransari, Mohadese Behzad
Summary: A numerical simulation study investigates the performance of a hybrid wind turbine design combining Darrieus and Savonius turbines. The study suggests three hybrid turbine designs, T-II, T-III, and T-IV, with the same Darrieus turbine. Results show that the power coefficient, C-p, varies differently with the tip speed ratio, TSR, for the hybrid turbines compared to the Darrieus turbine alone. The proposed T-IV turbine exhibits higher C-p than the base T-I turbine at the highest TSR.
Article
Mechanics
Amin Rasam, Zeinab Pouransari