The Applicability of Third Vortex Identification Methods on Atmospheric Boundary Layer and Wind Turbine Wakes

Abstract

To better understand the interaction between complex atmospheric boundary layer (ABL) inflow and wind turbine, the third vortex identification methods including the Liutex and OmegaR methods are implemented to identity and visualize the vortex structures, and the results are compared with those of Q criterion method. Two stages of numerical simulation are employed, including precursor stage for generation of ABL inflow and successor stage for wind turbine subjected to it. The wind turbine blades are modeled by actuator line model, and large eddy simulations are performed for the two stages. Compared with Q criterion method, the Liutex method can better identify vortices in ABL inflow and wind turbine wakes. However, the vortices in wind turbine wakes are not clearly visualized by OmegaR method due to its ability of capturing weak vortices. But the small-scale vortices in wind turbine wakes and large-scale vortices in ambient atmosphere are evident based on OmegaR method. Generation and fragmentation of blade tip vortices, interaction between vortices induced by wind turbine and ambient atmospheric vortices and wake expansion effect at middle wake region are clearly visualized by Q criterion and Liutex methods. The unphysical effect that sheet-like vortex structures upstream the wind turbine is wrongly captured by Q criterion method, whereas this error is eliminated by Liutex method.