In recent years, although the research on wind turbine wake has received widespread attention from the industry, the flow field characteristics of wind turbines are still difficult to fully understand because of the multi-scale flow field and the complexity of the flow. In the wake region of the wind turbine, the rotation effect of the blade is significant. There is a strong interference between the development of the wake vortex and the aerodynamic performance of the wind turbine, which makes it difficult to study the wind turbine. At the same time, the wake effect causes the wake field velocity to decrease and the turbulence degree to increase, so that the output power of the wind turbine decreases, the fatigue load of the blade increases, and the life span decreases. Therefore, the research on the near wake flow field of the wind turbine is indispensable.
At present, the most used model for numerical analysis is the Computational Fluid Dynamics (CFD) model. However, when the CFD model is used to simulate the wake characteristics of a wind turbine, it takes a large amount of computing resources and takes a long time.
Recently, the National Energy Wind Blade Research and Development Center of the Institute of Engineering Thermophysics of the Chinese Academy of Sciences has adopted a new model of engineering application (improved actuation surface model) independently developed to analyze the wake field of multiple wind turbines under different arrangements and to study interference. Effect effects, flow field dissipation, and blending.
This method uses volumetric force distribution in the computation domain to replace the effect of the blade on the fluid in the flow field. It does not need to solve the flow of the viscous boundary layer on the blade surface, reduces the number of grids near the blade, and greatly saves the modeling and numerical value. Solving the required time maximizes the analysis ability of the three-dimensional flow field.
Fig. 1 shows the calculation flow chart of the improved actuation surface model. The three-dimensional CFD calculation extracts the local attack angle and relative inflow velocity at different positions of the blade. According to the flow field information, the aeroelastic calculation is performed on the blade to obtain the current gas. Elasto-response; calculation of the local airfoil pressure coefficient distribution and conversion into the normal force of the airfoil plane is added to the flow field in the form of a volumetric force source term for iterative calculation.
Figure 2 shows the vortex cloud contour map and vorticity contour map of the multi-wind turbine under different arrangement patterns. The results show that the results of simulation of the wake field by the modified actuation surface model agree well with the existing model conclusions, and have high three-dimensional calculation accuracy. It is suitable for multi-fan wake research and can effectively simulate wake mixing and energy. Dissipation and other phenomena; At the same time, the analysis shows that the improvement of the wide application of the actuation surface model provides a reference for the aerodynamic characteristics of the near-tail flow field of the wind turbine and the development of the aerodynamic model.
The research was strongly supported by the National Natural Science Foundation of China (No. 51376180). The relevant research results have been published in the Journal of Engineering Thermophysics.
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