In a large wind farm,the wakes of upstream and downstream wind turbines can interfere with each other,affecting the overall power output of the wind farm.To further improve the numerical accuracy of the turbine wake d...In a large wind farm,the wakes of upstream and downstream wind turbines can interfere with each other,affecting the overall power output of the wind farm.To further improve the numerical accuracy of the turbine wake dynamics under atmosphere turbulence,this work proposes some improvements to the actuator line-large-eddy simulation(AL-LES)method.Based on the dynamic k-equation large-eddy simulation(LES),this method uses a precursor method to generate atmospheric inflow turbulence,models the tower and nacelle wakes,and improves the body force projection method based on an anisotropic Gaussian distribution function.For these three improvements,three wind tunnel experiments are used to validate the numerical accuracy of this method.The results show that the numerical results calculated in the far-wake region can reflect the characteristics of typical onshore and offshore wind conditions compared with the experimental results.After modeling the tower and nacelle wakes,the wake velocity distribution is consistent with the experimental result.The radial migration velocity of the tip vortex calculated by the improved blade body force distribution model is 0.32 m/s,which is about 6%different from the experimental value and improves the prediction accuracy of the tip vortex radial movement.The method proposed in this paper is very helpful for wind turbine wake dynamic analysis and wind farm power prediction.展开更多
The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swim...The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swimming,revealing insights into fish biomechanics in complex flows and assessing the environ-mental implications of marine energy solutions.We conducted numerical simulations with the URANS approach and k−ω−SST turbulence closuremodeltopredictthree-dimensionalturbulent flowinthe OpenFOAM software.The hydrokinetic rotor wake was simulated employing the actuator line method,providing a computationally efficient alternative to full geometry simulations.For accurate replication of the motion of a fish-like tuna(Thunnus atlanticus),dynamic adaptive mesh discretization was employed.The results offer a comparative analysis of fish swimming performance within the wake rotor,particularly when immersed in the tip blade vortex,contrasted with scenarios where fish swim in undisturbed flow conditions.The analysis encompasses three-dimensional wake structures,force generation,efficiency,and equilibrium states(balancing drag and thrust)across varying Swimming numbers(Sw).Key findings in-clude the enhanced attachment of the leading-edge vortex due to the caudal fin’s interaction with the tip blade vortex,resulting in improved auto-propulsive force production;a reduced tail stride frequency observed in fish swimming downstream of the rotor to achieve longitudinal force balance compared to unperturbed flow;and transverse hydrodynamic forces pushing fish radially away from the wake’s influ-ence zone,potentially mitigating the risk of collision with turbine blades.展开更多
基金Project supported by the National Key Research and Development Program of China(Nos.2019YFE0192600,2017YFE0132000,and 2019YFB1503700)the National Natural Science Foundation of China(Nos.51761135012 and 11872248)。
文摘In a large wind farm,the wakes of upstream and downstream wind turbines can interfere with each other,affecting the overall power output of the wind farm.To further improve the numerical accuracy of the turbine wake dynamics under atmosphere turbulence,this work proposes some improvements to the actuator line-large-eddy simulation(AL-LES)method.Based on the dynamic k-equation large-eddy simulation(LES),this method uses a precursor method to generate atmospheric inflow turbulence,models the tower and nacelle wakes,and improves the body force projection method based on an anisotropic Gaussian distribution function.For these three improvements,three wind tunnel experiments are used to validate the numerical accuracy of this method.The results show that the numerical results calculated in the far-wake region can reflect the characteristics of typical onshore and offshore wind conditions compared with the experimental results.After modeling the tower and nacelle wakes,the wake velocity distribution is consistent with the experimental result.The radial migration velocity of the tip vortex calculated by the improved blade body force distribution model is 0.32 m/s,which is about 6%different from the experimental value and improves the prediction accuracy of the tip vortex radial movement.The method proposed in this paper is very helpful for wind turbine wake dynamic analysis and wind farm power prediction.
文摘The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swimming,revealing insights into fish biomechanics in complex flows and assessing the environ-mental implications of marine energy solutions.We conducted numerical simulations with the URANS approach and k−ω−SST turbulence closuremodeltopredictthree-dimensionalturbulent flowinthe OpenFOAM software.The hydrokinetic rotor wake was simulated employing the actuator line method,providing a computationally efficient alternative to full geometry simulations.For accurate replication of the motion of a fish-like tuna(Thunnus atlanticus),dynamic adaptive mesh discretization was employed.The results offer a comparative analysis of fish swimming performance within the wake rotor,particularly when immersed in the tip blade vortex,contrasted with scenarios where fish swim in undisturbed flow conditions.The analysis encompasses three-dimensional wake structures,force generation,efficiency,and equilibrium states(balancing drag and thrust)across varying Swimming numbers(Sw).Key findings in-clude the enhanced attachment of the leading-edge vortex due to the caudal fin’s interaction with the tip blade vortex,resulting in improved auto-propulsive force production;a reduced tail stride frequency observed in fish swimming downstream of the rotor to achieve longitudinal force balance compared to unperturbed flow;and transverse hydrodynamic forces pushing fish radially away from the wake’s influ-ence zone,potentially mitigating the risk of collision with turbine blades.
