Full dynamic similarity experiments and predictive modeling of wind turbine aerodynamics across control strategies

Abstract: Wind turbines operate in turbulent atmospheric flow that constantly changes. In field tests, the full impacts of turbine design and operation are difficult to measure because confounding effects from atmospheric flow cannot be controlled. We address the gap in controlled experiments of wind turbines across control settings at dynamic similarity using a unique experimental framework that enables representative study of full-scale wind turbines in a laboratory-sized wind tunnel by pressurizing up to 220 atmospheres. This pressurization enables high-throughput experiments of a scaled wind turbine, at high Reynolds numbers and across yaw-misalignments and tip speed ratios relevant to commercial wind turbines. 

The results confirm that control strategies currently in use that were designed for turbines operating in ideal conditions without yaw misalignment should be modified, as the tip speed ratio that maximizes power depends on the yaw angle. Critically, the changes in forces and power with misalignment angle strongly depend on the tip speed ratio. We present a Unified Wind Turbine (UWT) model, which accurately predicts the behavior observed in these controlled experiments. The reliability of the UWT model to predict the synergistic effects of yaw misalignment and tip speed ratio enables its use in wind turbine design and wind farm flow control optimization to maximize the energy production and value of wind power systems. 

The cost-efficient experimental testbed in a pressurized wind tunnel presented herein offers a unique opportunity to study aerodynamics at dynamic similarity with large-scale, commercial turbines without many confounding effects and challenges faced in performing field tests.