Article
Computer Science, Interdisciplinary Applications
Huseyin C. Onel, Ismail H. Tuncer
Summary: The turbulent flow fields behind wind turbines were investigated using LES and Actuator Line Model, with critical model parameters determined through parametric studies. Wake interactions and blade performance were considered in simulations of turbulent flow behind wind turbines.
COMPUTERS & FLUIDS
(2021)
Review
Energy & Fuels
Zhaobin Li, Xiaohao Liu, Xiaolei Yang
Summary: This paper provides a review of existing wind turbine parameterization models, including the actuator disk, actuator line, and actuator surface models, and discusses their fundamental concepts, advanced issues, and applications in wind farms. It emphasizes the predictive capability of different models for different wake characteristics and highlights the importance of considering the effects of nacelle and tower in wind turbine wake predictions.
Article
Energy & Fuels
Luoqin Liu, Lucas Franceschini, Daniel F. Oliveira, Flavio C. C. Galeazzo, Bruno S. Carmo, Richard J. A. M. Stevens
Summary: We evaluated the accuracy of the actuator line model (ALM) approach for the NREL 5-MW wind turbine. The results showed that the power and thrust coefficients obtained using three large eddy simulation codes agree within 1% for a grid spacing of Delta grid <= 5.25 m. The ALM results converge towards blade element momentum (BEM) theory when the numerical resolution is increased.
Article
Mathematics, Applied
Zhiteng Gao, Ye Li, Tongguang Wang, Shitang Ke, Deshun Li
Summary: This study proposed improvements to the actuator line-large-eddy simulation method for more accurate modeling of wind turbine wake dynamics; utilized a precursor method to generate atmospheric inflow turbulence, modeled tower and nacelle wakes, and enhanced the body force projection method; wind tunnel experiments validated the numerical accuracy, showing good agreement with experimental results and improving prediction accuracy for wind turbine wake dynamics analysis and power prediction.
APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION
(2021)
Article
Green & Sustainable Science & Technology
Sam T. Fredriksson, Goran Brostrom, Bjorn Bergqvist, Johan Lennblad, Hakan Nilsson
Summary: The Deep Green technique for tidal power generation is suitable for moderate flows and operates typically at mid-depth, moving in a figure-eight path. A unique wake is created by Deep Green with increased bottom shear locally, and the flow disturbance can be scaled with its horizontal path width.
Article
Environmental Sciences
Inanc Senocak, Rey DeLeon
Summary: The concept of buoyancy perturbations with colored noise is investigated to trigger turbulence in upstream flows approaching complex terrain regions for accurate turbulent inflow generation. The application of this technique in predicting winds around Askervein and Bolund Hills shows that a common value for the bulk Richardson number works well for various flow problems. Additionally, it is found that the height of the perturbation box plays an important role in the accuracy of predictions around complex terrain, with good results obtained when the perturbation box height is a fraction of the Obukhov length scale.
Article
Engineering, Marine
Tengyuan Wang, Shuni Zhou, Chang Cai, Xinbao Wang, Zekun Wang, Yuning Zhang, Kezhong Shi, Xiaohui Zhong, Qingan Li
Summary: In this paper, the actuator line method combined with URANS is used to study the wake characteristics of a yawed wind turbine. The results show that a yawed wind turbine's wake exhibits deflection and deformation compared to an un-yawed wind turbine.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2023)
Article
Green & Sustainable Science & Technology
Brooke J. Stanislawski, Regis Thedin, Ashesh Sharma, Emmanuel Branlard, Ganesh Vijayakumar, Michael A. Sprague
Summary: As wind turbines become larger, the fluctuations in inflow have a significant impact on structural loading. The integral length scale, which represents the average size of the largest turbulent eddies, characterizes these fluctuations. Current design standards do not account for the varying integral length scales in turbine inflows. Using large-eddy simulations, we investigate the effects of turbulence with varying integral length scales on the loads of a 15-MW wind turbine. The results show that turbulence has a much greater impact on rotor and tower loads compared to mean shear profiles. Increasing the integral length scale can reduce blade root flapwise moments and rotor and tower loads. However, increasing the integral length scale beyond a certain point increases other loads and decreases some moments. Additionally, turbulence intensity has a larger influence on turbine loads than integral length scales. This study suggests that design standards should consider the varying integral length scales for accurate characterization of wind turbine loading in turbulent inflow conditions.
Article
Green & Sustainable Science & Technology
Zhiteng Gao, Ye Li, Tongguang Wang, Wenzhong Shen, Xiaobo Zheng, Stefan Probsting, Deshun Li, Rennian Li
Summary: The study introduces a new anisotropic body-force projection model in the actuator line model for wind-turbine wakes, showing that it can predict wakes more accurately and investigate wake characteristics under various yaw conditions. The research demonstrates the significant impact of nacelle effects on wind-turbine wakes, especially during yaw conditions.
Article
Engineering, Marine
Chengyong Zhu, Yingning Qiu, Yanhui Feng, Wei Zhong, Tongguang Wang
Summary: This paper investigates the rotational flow characteristics of the NREL Phase VI blade under axial and yawed inflow conditions using the DDES method. The rotational effects change the flow regime and suppress flow separation, leading to increased aerodynamic loads. The study shows that the rotational effects greatly influence the flow and aerodynamic performance of wind turbine blades, which can contribute to improved aerodynamic modeling.
Article
Thermodynamics
Li Li, Bing Wang, Mingwei Ge, Zhi Huang, Xintao Li, Yongqian Liu
Summary: The prediction of streamwise turbulence intensity distribution in wind farms is crucial for the micrositing of wind turbines. However, existing studies mostly focus on the superposition methods of velocity deficit in turbine wakes, while neglecting high-precision superposition models for turbulence intensity. This research uses large-eddy simulation to study the wakes of aligned wind turbines with different ground roughness heights and proposes a normalized superposition formula for turbulence intensity. Both simulations and experiments confirm that this method provides superior prediction accuracy compared to existing models, accurately predicting the distribution of streamwise turbulence intensity for aligned turbines.
Article
Energy & Fuels
Feifei Xue, Heping Duan, Chang Xu, Xingxing Han, Yanqing Shangguan, Tongtong Li, Zhefei Fen
Summary: The study investigated the impact of wakes on wind turbine performance and validated a modified actuator line model through experimental results. The findings indicated that staggered spacing affects the output power and thrust of wind turbines.
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
Ji Hao Zhang, Fue-Sang Lien, Eugene Yee
Summary: This study investigates the synergy effects in vertical-axis wind turbines (VAWTs) using an open-source code library. By modeling the turbines as momentum source terms in the Navier-Stokes equations, the computational cost is greatly reduced. The analysis and visualization of the power ratio provide a better understanding of VAWT synergy, and a novel approximation method for three-turbine synergy is proposed.
Article
Engineering, Civil
Zahra Mansouri, Rathinam Panneer Selvam, Arindam Gan Chowdhury
Summary: Defining the correct inlet boundary conditions is crucial in computational wind engineering, and synthetic inflow turbulence is a preferable approach due to its cost-effectiveness. This study investigates different synthetic turbulence generator methods and evaluates their performance in wind engineering applications. The results show that most methods produce spurious pressure, except for the Synthetic Eddy Method with the Gaussian shape function (SEM-G), which is found to be suitable for peak pressure prediction with a maximum error of 30%.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Meteorology & Atmospheric Sciences
Luca Lanzilao, Johan Meyers
Summary: Large eddy simulations (LESs) of the atmospheric boundary layer often use pseudo-spectral methods and a fringe-region approach for introducing inflow boundary conditions. However, this study shows that the standard fringe-region technique leads to spurious gravity waves and reflection of energy from the top of the domain, affecting the downstream velocity and pressure fields. To tackle this issue, a new fringe-region method that locally dampens the convective term in the vertical momentum equation is developed. The new method outperforms the standard approach and minimizes the impact on the surrounding flow.
BOUNDARY-LAYER METEOROLOGY
(2023)
Article
Computer Science, Interdisciplinary Applications
Nestor Ramos-Garcia, Aliza Abraham, Thomas Leweke, Jens Norkaer Sorensen
Summary: In this study, two flow models of the DTU vortex solver MIRAS were used to simulate the wake generated by a model wind turbine with varying levels of asymmetry. The predictions were validated against experimental measurements and visualizations. Good agreement was observed, especially with the higher-fidelity particle-mesh model, which closely predicted the flow features observed in the experiments. The analysis also revealed that rotor asymmetry triggers a vortex instability, known as leapfrogging, which accelerates the breakdown of tip vortices and promotes faster wake recovery.
COMPUTERS & FLUIDS
(2023)
Article
Automation & Control Systems
Jakob Harzer, Jochem De Schutter, Moritz Diehl, Johan Meyers
Summary: Dynamic soaring is a flight technique that enables periodic flight patterns using wind gradients. This paper investigates the use of wind turbine wakes for dynamic soaring and explores their potential for wake revitalization. Optimal control based on a simplified model is used to compute optimal trajectories for different wing spans and mass-scaling assumptions. The results show promising wake revitalization capabilities using dynamic soaring in wind turbine wakes.
EUROPEAN JOURNAL OF CONTROL
(2023)
Article
Computer Science, Interdisciplinary Applications
Liang Fang, Stefan Vandewalle, Johan Meyers
Summary: Multiple shooting methods have been rapidly developed as a promising approach to optimize the solution to optimal control problems. In this study, we propose a new multiple shooting algorithm based on a sequential quadratic programming method, which is suitable for large-scale time-dependent PDEs. We analyze the KKT matrix structure and solve the large-scale KKT system using a preconditioned conjugate gradient algorithm. The algorithm is validated on two control problems and achieves considerable accelerations compared to single shooting approaches.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
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
Energy & Fuels
Frederik Aerts, Luca Lanzilao, Johan Meyers
Summary: This study proposes a Bayesian uncertainty quantification framework for improving wind farm models. The framework successfully distinguishes the three sources of uncertainty in the parameters and allows for model calibration and validation.
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
T. Bon, D. Broos, R. B. Cal, J. Meyers
Summary: The structure and impact of thermally induced secondary motions in stably stratified channel flows with two-dimensional surface temperature inhomogeneities were studied using direct numerical simulation (DNS). The length of the temperature strips affects the streamwise development of the secondary flows, and they reach a fully developed state after approximately 25 strip widths. The strength of the secondary motions and their impact on momentum and heat transfer decrease as the length of the temperature strips decreases, becoming negligible when the strip width approaches 1.
JOURNAL OF FLUID MECHANICS
(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
Green & Sustainable Science & Technology
Jens N. Sorensen
Summary: A new generalized analytical model for representing body forces in numerical actuator disc models of wind turbines is proposed and compared to results from a blade element momentum (BEM) model. The model is validated for different wind turbines operating under a wide range of operating conditions, showing generally excellent agreement with the BEM model even at very small thrust coefficients and tip-speed ratios.
WIND ENERGY SCIENCE
(2023)
Proceedings Paper
Energy & Fuels
Jens N. Sorensen, Gunner C. Larsen
Summary: A study was conducted to evaluate the potential of offshore wind power in the North Sea, including the prediction of wind resources and associated costs. The study considered factors such as turbine size, distance between turbines, wind resources, and water depths. The findings indicate that exploiting 180,000 km(2) of the North Sea with 60,000 20 MW wind turbines could generate electricity equivalent to Europe's consumption at a cost of 6.2 cents/kWh. Additionally, increasing the number of turbines in the same area can capture more energy but at a higher cost.
WAKE CONFERENCE 2023
(2023)
Proceedings Paper
Energy & Fuels
Aliza Abraham, Nestor Ramos-Garcia, Jens Norkaer Sorensen, Thomas Leweke
Summary: The study investigates the use of rotor asymmetry as a passive method for mitigating the detrimental effects of tip vortices in wind turbine wakes. It is found that the asymmetric rotor successfully triggers the instability, increasing the wake average velocity by a maximum of 3.5% and the power available to a downstream turbine by up to 11%. The findings suggest that rotor asymmetry has strong potential as a wake control method and should be further investigated for its effects on inflow turbulence and rotor loading.
WAKE CONFERENCE 2023
(2023)
Article
Green & Sustainable Science & Technology
Gonzalo Pablo Navarro Diaz, Alejandro Daniel Otero, Henrik Asmuth, Jens Norkaer Sorensen, Stefan Ivanell
Summary: Two new variants of the actuator line technique are proposed to simulate transient wind turbine wake interaction problems using generic load data. The models only require thrust and power coefficients, and the tip speed ratio as input parameters. The proposed models are compared to the actuator disk model and the classical actuator line model based on blade element theory, showing their effectiveness.
WIND ENERGY SCIENCE
(2023)
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)