Article
Energy & Fuels
Xin Liu, Lailong Li, Shaoping Shi, Xinming Chen, Songhua Wu, Wenxin Lao
Summary: This study investigated the wake intensity of Huaneng Rudong 300 MW offshore wind farm using a Gaussian wake model, which can predict the characteristics accurately and showed a difference mostly under 10% when compared with the actuator line (AL)-based LES method.
Article
Green & Sustainable Science & Technology
W. Chanprasert, R. N. Sharma, J. E. Cater, S. E. Norris
Summary: This study investigates the influence of directionally sheared inflows on wake interaction in a four-inline turbine array using a coupled Large Eddy Simulation (LES) and turbine aeroelastic code. The results show that the lateral velocity of the ambient wind affects wake rotations, resulting in differences in radial wake expansion and wake shape twist angle. Symmetric wakes in the zero directional shear case lead to lower fatigue loads on the blades and rotor shaft compared to skewed wakes. The flapwise blade-root bending moment of downstream turbines is approximately three times higher under wind veering (Northern Hemisphere) than under wind backing (Southern Hemisphere).
Article
Engineering, Marine
Jiufa Cao, Zhaojie Qin, Xiang Gao, Tianmei Pu, Weijun Zhu, Shitang Ke, Xiang Shen
Summary: The large-scale development of wind farms has resulted in the formation of wind farm clusters, especially offshore wind farms, which have significant wake and cluster effects on downstream wind farms. This study uses Large Eddy Simulation (LES) combined with actuator line model to analyze the aerodynamic performance and wake effect of a wind farm cluster. The results show that increasing the distance between wind farms reduces the cluster effect, with 30D being a reasonable separation distance. The study also finds that staggering wind farms in a cluster improves the overall power generation.
Article
Energy & Fuels
Hyebin Kim, Sang Lee
Summary: This study investigates the influence of yaw control on the wake structure behind a wind turbine using large-eddy simulation. The results show that the deformation of the wake is caused by the interaction between the global wake rotation and a counter-rotating vortex pair induced by the yaw angle. The yaw angle has a significant impact on the wake distortion and trajectory, which naturally diminishes with increasing downstream distance.
Article
Green & Sustainable Science & Technology
Mingwei Ge, Dennice F. Gayme, Charles Meneveau
Summary: The study investigates the flow properties of wind turbines operating behind a building-like wall-attached cube through large-eddy simulation, revealing significant power losses and fluctuations for the first turbine downstream of the cube. Improved recovery of the turbine wake is observed, attributed to enhanced turbulent transport and convection associated with the secondary mean flow structure behind the cube.
Article
Green & Sustainable Science & Technology
Jessica M. I. Strickland, Srinidhi N. Gadde, Richard J. A. M. Stevens
Summary: This study investigates wind farm blockage in a stable atmospheric boundary layer using large eddy simulations. The results show that wind farm blockage increases under stable atmospheric conditions, primarily due to the deflection of cold airflow creating a high-pressure region in front of the wind farm.
Article
Energy & Fuels
Xiaolei Yang, Christopher Milliren, Matt Kistner, Christopher Hogg, Jeff Marr, Lian Shen, Fotis Sotiropoulos
Summary: The article highlights the importance and complexity of characterizing wind fields at high temporal and spatial resolutions, proposing the integration of field measurements and high-fidelity large-eddy simulation to improve the characterization of wind fields in utility-scale wind farms.
Article
Energy & Fuels
Xiaolei Yang, Christopher Milliren, Matt Kistner, Christopher Hogg, Jeff Marr, Lian Shen, Fotis Sotiropoulos
Summary: The research demonstrates the potential of integrating field measurements and high-fidelity large-eddy simulation (LES) for improved characterization of the wind fields in utility-scale wind farms. The probability density function (PDF) of wind speeds in turbine wakes can be reasonably represented using the Weibull distribution. Comparisons between LES predictions and measured data show good agreement for mean wind speed and turbulence intensity.
Article
Energy & Fuels
Jagdeep Singh, Jahrul M. Alam
Summary: In this article, the influence of spatial heterogeneity on wind turbine performance in wind farms is investigated. It is found that rough topography significantly enhances the power production of large wind farms, and the primary degree of spatial heterogeneity is in the streamwise direction. The study reveals the importance of considering the effects of complex terrain on wind turbine and wind farm design to improve their efficiency and energy output.
Article
Green & Sustainable Science & Technology
Xuan Dai, Da Xu, Mengqi Zhang, Richard J. A. M. Stevens
Summary: In this study, dynamic mode decomposition (DMD) is used to analyze and reconstruct the flow field in large-scale numerically simulated wind farms, finding that a combination of horizontal and vertical staggering improves wind farm performance. The sparsity-promoting (SP) DMD method shows smaller performance loss compared to the amplitude selection (AP) DMD method in terms of flow field reconstruction.
Article
Thermodynamics
Guo-Wei Qian, Yun-Peng Song, Takeshi Ishihara
Summary: The study developed a control-oriented large eddy simulation (LES) code to predict wind turbine wake, and validated the results with both laboratory and utility-scale wind turbines. The simulation results showed good agreement with experimental data, demonstrating the effectiveness of the LES code in predicting wake dynamics for different scales of wind turbines.
Article
Energy & Fuels
Sicheng Wu, Cristina L. L. Archer, Jeffrey D. D. Mirocha
Summary: In this study, LES model and WRF model with actuator disk model were used to investigate wake effects of wind turbines. The wake was found to have a dual nature, with wind speed deficit and added TKE behaving differently and not co-located in space. Temperature changes near the ground are driven by added TKE and atmospheric stability. Wakes do not expand indefinitely but eventually stop expanding and may even contract, depending on atmospheric stability.
Article
Green & Sustainable Science & Technology
Jian Wei Lin, Wei Jun Zhu, Wen Zhong Shen
Summary: In this paper, two new analytical wake models are developed to predict the wind velocity distribution in the wake region of a wind turbine. These models are validated and compared with existing engineering wake models, showing lower relative errors and better performance. They are recommended for wind farm design.
Article
Thermodynamics
Tian Li, Zhenqing Liu, Hao Wang, Weifu Bian, Qingshan Yang
Summary: The wake characteristics of wind turbines mounted on complex terrains are affected by the ground roughness and atmospheric stratification. Depending on the shape of the terrain, the effects of these two factors can either be superimposed or counteracted. Atmospheric stratification significantly reduces the power of wind turbines, while rough ground has a smaller impact on power production. The micrositing of wind turbines strongly affects the wake characteristics and power production on complex terrains with atmospheric stratification.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Engineering, Mechanical
Vahid Mazidi Sharafabadi, Mani Fathali
Summary: This study predicts four different subgrid-scale (SGS) models in large eddy simulation (LES) of large wind farms. The impact of these models on the large wind farm simulation is evaluated by studying various parameters such as mean flow velocity, wake characteristics, wind turbine power extraction, and mean kinetic energy budget terms. The results show that different models lead to different power extraction and discrepancies in the mean kinetic energy budget terms, particularly the dissipation term between the Smagorinsky and dynamic models.
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Majid Bastankhah, Carl R. Shapiro, Sina Shamsoddin, Dennice F. Gayme, Charles Meneveau
Summary: Motivated by the need to mitigate power reduction and unsteady loading of downstream turbines, this study develops an analytical model to predict the shape of curled wakes. By estimating the vorticity distribution at the wake edge and considering the wake as a vortex sheet, the model describes the time evolution of the wake shape. The model is validated against simulations and experiments, and shows a universal solution for curled wakes with suitable dimensionless variables.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: A large eddy simulation wall model is developed based on a formal interpretation of quasi-equilibrium that governs momentum balance. The model includes a relaxation time scale that ensures self-consistency with assumed quasi-equilibrium conditions. The new approach allows for formally distinguishing between quasi-equilibrium and additional, non-equilibrium contributions to wall stress.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Kristofer M. Womack, Ralph J. Volino, Charles Meneveau, Michael P. Schultz
Summary: This study conducted experiments on flows with regular and random roughness elements and found that there were minor differences in flow statistics between the regular and random arrangements at the same density. The observed differences in surface flow parameters were mainly due to the presence of secondary flows. Contrary to expectations, these secondary flows were present over the random surfaces and not discernible over the regular surfaces. Additionally, the local turbulent boundary layer profiles did not scale with local wall shear stress but appeared to scale with local turbulent shear stress above the roughness canopy.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
A. K. Aiyer, C. Meneveau
Summary: In this study, the dispersion characteristics of slightly buoyant droplets in a turbulent jet were investigated using large eddy simulations (LES). The model accurately captured the differential, size-based dispersion characteristics of the droplets with finer grid resolutions. Moreover, similarity solution and subgrid-scale models were used to predict the concentration profiles and turbulent concentration flux of the droplets, and the results showed good agreement with experimental data and high-resolution LES simulations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Yuan Luo, Yipeng Shi, Charles Meneveau
Summary: The study demonstrates that equivalent predictions can be obtained by recursively modulating model terms at a single level instead of integrating the stochastic model at multiple levels and scales. The statistical properties of the model compare well with direct numerical simulation and experimental data.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Wen Wu, Charles Meneveau, Rajat Mittal, Alberto Padovan, Clarence W. Rowley, Louis Cattafesta
Summary: The response of a turbulent separation bubble to zero-net-mass-flux actuation is investigated via direct numerical simulations. The results demonstrate that the length of the separation bubble can be reduced by forming vortex pairs at the appropriate excitation frequencies. In addition, the time-averaged structures exhibit a high sensitivity to the actuation.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Mostafa Aghaei-Jouybari, Jung -Hee Seo, Junlin Yuan, Rajat Mittal, Charles Meneveau
Summary: The force partitioning method is used to analyze the pressure-induced drag for turbulent flow over rough walls. The study quantifies the contributions of rotation-dominated vortical regions and strain-dominated regions to the pressure drag, and investigates the effects of surface geometry on drag. The results suggest that the phi field, which encodes surface geometry, can be used to parametrize the surface drag.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Samvit Kumar, Charles Meneveau, Gregory Eyink
Summary: A model for the structure function tensor was proposed, incorporating the effect of anisotropy as a linear perturbation to the standard isotropic form. The analysis extends the spectral approach proposed by Ishihara et al., and valid in the inertial range of turbulence. Observations were made regarding the countergradient correlation between Fourier modes of wall-normal and streamwise velocity components near the Kolmogorov scale.
PHYSICAL REVIEW FLUIDS
(2022)
Editorial Material
Mechanics
Charles Meneveau, Colm-Cille P. Caulfield
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Ghanesh Narasimhan, Dennice F. Gayme, Charles Meneveau
Summary: Large eddy simulations are used to study the effects of veer on wind turbine wakes in the atmospheric boundary layer. The study finds that veer causes sideways wake deformation, but this can be predicted using a simple correction.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Multidisciplinary
Yinghe Qi, Charles Meneveau, Greg A. Voth, Rui Ni
Summary: Fluid elements in turbulence deform through stretching and folding. The dynamics of folding are depicted by projecting the material deformation tensor onto the largest stretching direction and tracking the evolution of material curvature. Direct numerical simulations reveal that curvature growth exhibits two stages: a linear stage dominated by folding of fluid elements through persistent velocity Hessian, followed by an exponential-growth stage driven by stretching of already strongly bent fluid elements. This transition leads to strong curvature intermittency, which can be explained by a proposed curvature-evolution model. The link between velocity Hessian and folding provides a new understanding of the energy cascade and mixing in turbulence beyond the traditional linear stretching dynamics.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Ruifeng Hu, Perry L. Johnson, Charles Meneveau
Summary: This paper introduces a generalized dynamic resuspension model for particles rolling on a surface with fractal-like multiscale roughness elements, called the multiscale asperity model (MSAM). Non-Gaussian stochastic models are compared with a Gaussian stochastic model for the flow velocity seen by a particle. The results show that the non-Gaussian stochastic flow models improve the prediction of the fraction of particles remaining on the wall after a given exposure time to turbulent flow.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Hanxun Yao, Tamer A. Zaki, Charles Meneveau
Summary: Based on the generalized local Kolmogorov-Hill equation, this study examines the definition of entropy and entropy generation for turbulence. The results from direct numerical simulations confirm the validity of the fluctuation relation in non-equilibrium thermodynamics for turbulent flows in the inertial range.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Environmental Sciences
James C. McWilliams, Charles Meneveau, Edward G. Patton, Peter P. Sullivan
Summary: Recent high-resolution large-eddy simulations of a stable atmospheric boundary layer are analyzed and compared with observations. The simulations are judged to be converged based on the collapse of vertical profiles of winds, temperature, and turbulence moments. The subfilter-scale motions extracted from the simulations are in good agreement with observations. The data from the simulations will be made available to the research community.
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: The recent LaRTE approach is a wall model for large-eddy simulations (LES) that separates equilibrium and non-equilibrium wall-stress dynamics. The model shows good agreement with various non-equilibrium channel flows and provides insights into wall-stress physics.
JOURNAL OF FLUID MECHANICS
(2023)