Date

2016

Document Type

Thesis

Degree

Master of Science

Department

Computational and Engineering Mechanics

First Adviser

Banerjee, Arindam

Abstract

Tidal turbines when subjected to a yawed inflow experience a deficit in its performance. In addition, the yawed inflow affects the downstream wake propagation and subsequent recovery. A detailed three-dimensional computational fluid dynamics study was performed using a SST turbulence model with curvature correction for a three bladed, constant chord, untwisted tidal turbine operating at uniform inflow of 0.73m/s. The yaw angle to the turbine is varied from 0° to 15°; an increase in yaw over this range caused a power coefficient deficit of 26% and a thrust coefficient deficit of ~ 6% at a TSR value of 5 which corresponds to the maximum power coefficient for the turbine. Wake propagation was studied up to a downstream distance of 10R for all cases; a skewness in the wake, proportional to the yaw angle was observed. Flow accelerating around the turbine rotor plane interacts with the skewed wake, helping in faster recovery of velocity inside the wake at higher yaw. Second order moments in the wake were also investigated. The propagating wake was noticed to twine around the turbine centerline with increasing downstream distance and deviate ~5° towards the free surface above the turbine centerline for the case of 15º yaw. The center of the wake was also tracked to better understand downstream wake propagation; with an increase in yaw, the wake recovery distance is noticed to decrease and the flow behind and around the turbine rotor is observed to be increasingly turbulent and experiencing high Reynolds stress values.

Available for download on Sunday, October 28, 2018

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