Wind-tunnel blockage corrections for wind-turbine measurements
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Wind-tunnel measurements are an important step during the wind-turbine design process. The goal of wind-tunnel tests is to estimate the operational performance of the wind turbine, for example by measuring the power and thrust coefficients. Depending on the sizes of both the wind turbine and the test section, the effect of blockage can be substantial. Correction schemes for the power and thrust coefficients have been proposed in the literature, but for high blockage and highly loaded rotors these correction schemes become less accurate.
A new method is proposed here to calculate the effect a cylindrical wind-tunnel test section has on the performance of the wind turbine. The wind turbine is modeled with a simplified vortex model. Using vortices of constant circulation to model the wake vortices, the performance characteristics are estimated. The test section is modeled with a panel method, adapted for this specific situation. It uses irrotational axisymmetric source panels to enforce the solid-wall boundary condition. Combining both models in an iterative scheme allows for the simulation of the effect of the presence of the test-section walls on wind turbines performance.
Based on the proposed wind-tunnel model, a more general empirical correlation scheme is proposed to estimate the performance characteristics of a wind turbine operating under unconfined conditions by correcting the performance measured in the confined wind-tunnel configuration. The proposed correction scheme performs better than the existing correction schemes, including cases with high blockage and highly loaded rotors.
Place, publisher, year, edition, pages
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-138602OAI: oai:DiVA.org:kth-138602DiVA: diva2:681524
2013-06-19, 10:27 (English)
Segalini, Antonio, Dr.
Alfredsson, Henrik, Professor