Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillati...Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillation of the far wake.Triadic interactions,the mechanism of energy transfers between scales,manifest as triples of wavenumbers or frequencies and can be characterized through bispectral analyses.The bispectrum,which correlates the two frequencies to their sum,is calculated by two recently developed multi-dimensional modal decomposition methods:scale-specific energy transfer method and bispectral mode decomposition.Large-eddy simulation of a utility-scale wind turbine in an atmospheric boundary layer with a broad range of large length-scales is used to acquire instantaneous velocity snapshots.The bispectrum from both methods identifies prominent upwind and wake meandering interactions that create a broad range of energy scales including the wake meandering scale.The coherent kinetic energy associated with the interactions shows strong correlation between upwind scales and wake meandering.展开更多
The vorticity dynamics and its relationship to dissipation in the wake of a utility-scale wind turbine are investigated through large-eddy simulation.The vorticity dynamics is assessed through the enstrophy,which is r...The vorticity dynamics and its relationship to dissipation in the wake of a utility-scale wind turbine are investigated through large-eddy simulation.The vorticity dynamics is assessed through the enstrophy,which is related to the turbulent dissipation.The averaged enstrophy and turbulent dissipation are shown to be quantitatively similar in the wake.Using temporal phase averaging,the vorticity fluctuations are decomposed into coherent and random fluctuations with respect to the frequency of the tip vortices.The enstrophy in the tip vortices is dominated by coherent fluctuations,while the coherent fluctuations of root vortices are immediately saturated by the random vorticity fluctuations of the unstable hub vortex.The coherent strain rate has significant differences com pared to the coherent enstrophy within one diameter downwind of blade tip,but the random enstrophy and strain rate are relatively similar.Differences in coherent enstrophy and strain rate decrease further from the rotor.展开更多
基金supported by the National Science Foundation(Grant No.21-36371)supported by the National Science Foundation(Grant Nos.21-38259,21-38286,21-38307,21-37603,and 21-38296)。
文摘Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillation of the far wake.Triadic interactions,the mechanism of energy transfers between scales,manifest as triples of wavenumbers or frequencies and can be characterized through bispectral analyses.The bispectrum,which correlates the two frequencies to their sum,is calculated by two recently developed multi-dimensional modal decomposition methods:scale-specific energy transfer method and bispectral mode decomposition.Large-eddy simulation of a utility-scale wind turbine in an atmospheric boundary layer with a broad range of large length-scales is used to acquire instantaneous velocity snapshots.The bispectrum from both methods identifies prominent upwind and wake meandering interactions that create a broad range of energy scales including the wake meandering scale.The coherent kinetic energy associated with the interactions shows strong correlation between upwind scales and wake meandering.
文摘The vorticity dynamics and its relationship to dissipation in the wake of a utility-scale wind turbine are investigated through large-eddy simulation.The vorticity dynamics is assessed through the enstrophy,which is related to the turbulent dissipation.The averaged enstrophy and turbulent dissipation are shown to be quantitatively similar in the wake.Using temporal phase averaging,the vorticity fluctuations are decomposed into coherent and random fluctuations with respect to the frequency of the tip vortices.The enstrophy in the tip vortices is dominated by coherent fluctuations,while the coherent fluctuations of root vortices are immediately saturated by the random vorticity fluctuations of the unstable hub vortex.The coherent strain rate has significant differences com pared to the coherent enstrophy within one diameter downwind of blade tip,but the random enstrophy and strain rate are relatively similar.Differences in coherent enstrophy and strain rate decrease further from the rotor.
