An Analytical Model of Wake Deflection Due to Shear Flow

An Analytical Model of Wake Deflection Due to Shear Flow

Micallef, D.
Simao Ferreira, C.J.
Sant, T.
Van Bussel, G.J.W.

Aerospace Engineering

Aerodynamics, Wind Energy & Propulsion

2010-06-28

The main motivation behind this work is to create a purely analytical engineering model for wind turbine wake upward deflection due to shear flow, by developing a closed form solution of the velocity field due to an oblique vortex ring. The effectiveness of the model is evaluated by comparing the results with those of a free-wake model. The solution of the velocity field due to an oblique vortex ring is obtained by using the result of an upright ring along with an equivalent point method. The wake model is derived using oblique ring elements with a number of suitable assumptions. Results of wake vertical deflection are compared with a free-wake solution. A linear trend between wake deflection and shear flow exponent is found with both models. The oblique ring model shows some discrepancies from the free-wake result in terms of the dependence of the deflection on the reference tip speed ratio. The oblique ring model needs further refinements and validation with experimental work and is only currently suited for the determination of general wake kinematics. It however provides immediate results for a given input and can be useful in generating databases with wake geometry information.

horizontal axis wind turbines
atmospheric shear flow
vortex rings

http://resolver.tudelft.nl/uuid:7b821f51-8fd7-43ee-aedf-1bbd3a3e6b54

European Wind Energy Association

3rd EWEA Conference - Torque 2010: The Science of making Torque from Wind, Heraklion, Crete, Greece, 28-30 June 2010

Institutional Repository

conference paper

(c) 2010 The Author(s)