An experimental assessment of analytical blockage corrections for turbines

Abstract

In laboratory experiments involving wind or water turbines, it is often desirable to correct measured performance for the effects of model blockage. However, there has been limited experimental validation of the analytical blockage corrections presented in the literature. Therefore, the objective of this study is to evaluate corrections against experimental data and recommend one or more for future use. For this investigation, we tested a cross-flow turbine and an axial-flow turbine under conditions of varying blockage with other non-dimensional parameters, such as the free-stream Reynolds and Froude numbers, held approximately constant. We used the resulting experimental data to assess the effectiveness of multiple analytical blockage corrections for both turbine types. Of the corrections evaluated, two are recommended. However, as these methods are based on axial momentum theory, we observe that corrections are more effective for thrust than power. We also find that increasing blockage changes the local Reynolds number, which can affect turbine performance but is not reflected in axial momentum theory.