Abstract
A novel analytical model is proposed and validated in this paper to predict the velocity deficit in the wake downwind of a wind turbine. The model is derived by employing mass and momentum conservation and assuming a cosine-shaped distribution for the velocity deficit. In this model, a modified wake growth rate rather than a constant one is chosen to take into account the effects of the ambient turbulence and the mechanical turbulence generated. The model was tested against field observations, wind-tunnel measurements in different thrust operations and high-resolution large-eddy simulations (LES) for two aerodynamic roughness lengths. It was found that the normalized velocity deficit predicted by the proposed model shows good agreement with experimental and numerical data in terms of shape and magnitude in the far wake region ( x / d 0 > 3 ). Based on the proposed model, predictions from multiple views and at different locations are demonstrated to show the spatial distribution of streamwise velocity downwind of a wind turbine. The result shows that the model is suitable for predicting streamwise velocity fields and thus could provide some references for the selection of wind turbine spacing.
Highlights
Wind energy is one of the most profitable renewable resources and is expected to develop substantially all over the world [1]
Wind turbines in wind farms have to operate in the downwind wake flow which is characterized by lower mean velocity and higher turbulence intensity than those under unaffected conditions
Wind-turbine wakes lead to overall power losses in large wind farms and increased fatigue loading on turbines [2,3,4]
Summary
Wind energy is one of the most profitable renewable resources and is expected to develop substantially all over the world [1]. Due to the need for large wind farm installation, wind-turbine wake has become a significant topic in wind energy [5] and many researchers have conducted extensive research on turbine wakes via approaches such as field observations, wind-tunnel tests and numerical simulations. Experimental and numerical approaches are powerful tools in the research of wind-turbine wakes, physically-based analytical models are still extensively used to estimate wake deficit and power production because of their simplicity, good. The analytical wake model is an efficient and useful tool with which to evaluate wake-turbine flows and wake effects on power generation. It has played a significant role in the wind energy community
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