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An analysis of some aerodynamic effects in Horizontal Axis Wind Turbines

Kooiman, A. (2014) An analysis of some aerodynamic effects in Horizontal Axis Wind Turbines.

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Abstract:The goal of this project was to gain insight in ow phenomena for horizontal axis wind turbines (HAWT). In order to predict the performances of a wind turbine, it was important to know the forces that act on the blades. A way of predicting the forces on a wind turbine is to use a blad element momentum (BEM) model as implemented in FAST. In this project the results of the MEXICO wind tunnel experiments have been validated in order to gain insight in important flow phenomena. The characteristics of a ow depends on whether the flow is attached to the blade. A distinction between attached flow, partly separated flow and fully separated flow was made. Whether a flow is attached is dependant on the angle of attack. Rotational augmentation is important at high tip speed ratio and close to the hub. Rotational augmentation causes attached flow for higher angles of attack than it would have according to the lift properties of an airfoil in 2D steady flow. This causes higher lift coefficients for these angles of attack, since the lift keeps increasing with the angle of attack. Yawed in flow induces the effect of dynamic stall, since dynamic stall is caused by a rapidly changing angle of attack. Dynamic stall causes the forces to deviate from the static lift and drag curves. Characteristic for this phenomena is that sudden drops in lift can appear, du to a vortex that gets downstream of the trailing edge.
Item Type:Internship Report (Master)
Instituto Superior Técnico, Portugal
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:MEXICO experiment, FAST, HAWT, Rotational augmentation, yaw, dynamic stall
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