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Diffuser Augmented Wind Turbines (DAWTs) have been a highlight of research in small size wind turbines due to their potential capability of exceeding Betz Limit. Bringing a wall in close proximity of blade tip may have strong influences on physics of tip leakage flow. In current study, the effect of the diffuser wall on tip leakage flow is examined. Different tip gap to diffuser radius ratios are numerically studied in a two dimensional domain. As tip leakage flow in DAWTs has not been studied before, the methodology for the current work is adopted from similar research in gas turbines. Obtained results indicate that as the tip gap to diffuser radius ratio is reduced from 0.067 to 0.02, tip leakage mass flow rate reduces to 6% and the total pressure loss increases by 56%. This behavior of tip leakage flow is further elaborated by discussing the flow physics in the gap region.
CFD, DAWT, flow separation, tip leakage
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