Modeling the induction, thrust, and power of a yaw misaligned actuator disk

TL;DR

This paper develops an analytical model for yaw misaligned wind turbines based on extended momentum theory, improving predictions of thrust, power, and wake behavior, and demonstrating benefits of combined wake steering and induction control.

Contribution

It introduces a novel analytical model for yawed turbines that accounts for induction effects, enabling better prediction and optimization of wind farm performance.

Findings

The model accurately predicts thrust, wake velocity, and power for yawed turbines.

Power output exceeds traditional $ ext{cos}^3( ext{yaw})$ estimates due to induction effects.

Combining wake steering and induction control enhances overall wind farm energy production.

Abstract

Collective wind farm flow control, where wind turbines are operated in an individually suboptimal strategy to benefit the aggregate farm, has demonstrated potential to reduce wake interactions and increase farm energy production. However, existing wake models used for flow control often estimate the thrust and power of yaw misaligned turbines using simplified empirical expressions which require expensive calibration data and do not accurately extrapolate between turbine models. The thrust, wake velocity deficit, wake deflection, and power of a yawed wind turbine depend on its induced velocity. Here, we extend classical one-dimensional momentum theory to model the induction of a yaw misaligned actuator disk. Analytical expressions for the induction, thrust, initial wake velocities, and power are developed as a function of the yaw angle and thrust coefficient. The analytical model is validated against large eddy simulations of a yawed actuator disk. Because the induction depends on the yaw and thrust coefficient, the power generated by a yawed actuator disk will always be greater than a $\cos^3(\gamma)$ model suggests, where $\gamma$ is yaw. The power lost by yaw depends on the thrust coefficient. An analytical expression for the thrust coefficient that maximizes power, depending on the yaw, is developed and validated. Finally, using the developed induction model as an initial condition for a turbulent far-wake model, we demonstrate how combining wake steering and thrust (induction) control can increase array power, compared to either independent steering or induction control, due to the joint dependence of the induction on the thrust coefficient and yaw angle.