An investigation into wake and solid blockage effects of Vertical-Axis Wind Turbines (VAWTs) in closed test-section wind tunnel testing is described. Static wall pressures have been used to derive velocity increments along a wind tunnel test-section which in-turn are applied to provide evidence of wake interference characteristics of rotating bodies interacting within this spatially restricted domain. Vertical-axis wind turbines present a unique aerodynamic obstruction in wind tunnel testing whose blockage effects have not been extensively investigated.
The flow-field surrounding these wind turbines is asymmetric, periodic, unsteady, separated and highly turbulent. Static pressure measurements are taken along a test-section sidewall to provide a pressure signature of the test models under varying rotor tip-speed ratios (freestream conditions and model RPM’s). To provide some guidance on the scaling of the combined effects of wake and solid blockage, wake characteristics and VAWT performance produced by the same vertical-axis wind turbine concept have been tested at different physical scales in two different wind tunnels. This investigation provides evidence of the effects of large wall interactions and wake propagation caused by these models at well below generally accepted standard blockage figures.