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Ocean Engineering

A Discrete Vortex Method for Simulating a Stand-Alone Tidal-Current Turbine: Modeling and Validation

[+] Author and Article Information
Ye Li1

Department of Mechanical Engineering, University of British Columbia, 6250 Applied Sciences Ln, Vancouver, BC, V6T1Z4, Canadaye.li@nrel.gov

Sander M. Çalışal

Department of Mechanical Engineering, University of British Columbia, 6250 Applied Sciences Ln, Vancouver, BC, V6T1Z4, Canada

This method is a discrete-vortex method. We call it as DVM-UBC because it was developed by the researchers in the University of British Columbia (UBC).

The Reynolds number in the numerical simulation is calculated with respect to incoming flow velocity and blade chord length.

Design TSR refers to the TSR range for which the turbine is designed and under which the power coefficient of the turbine is around its maximum value.

In the conformal mapping method, the Reynolds number is infinite.

One might also notice that the turbine simulated using FLUENT has a shaft for the purpose of approximating the turbine in experimental test.

The turbine tested in UBC towing tank has two arms and a shaft and the turbine simulated in FLUENT has a shaft.

The measured torque of one-blade turbine fluctuates significantly. One cannot easily make a judgment about the shift. Comparing the troughs and the peaks between the experimental results and the numerical results, the shifts are slightly different.

The dynamic result is proportional to the velocity square while the kinematics result is proportional to the velocity.

1

Present address: National Wind Technology Center, National Renewable Energy Laboratory, 1617 Cole Blvd., MS 3811, Golden, CO 80401.

J. Offshore Mech. Arct. Eng 132(3), 031102 (Apr 07, 2010) (9 pages) doi:10.1115/1.4000499 History: Received December 01, 2008; Revised September 15, 2009; Published April 07, 2010; Online April 07, 2010

This paper advanced our recent effort (Li and Çalışal, 2007, “Preliminary Result of a Discrete Vortex Method for Individual Marine Current Turbine,” The 26th ASME International Conference on Offshore Mechanics and Arctic Engineering, Jun. 10–15, San Diego, CA) to study the behavior of tidal-current turbines. We propose a discrete-vortex method with free-wake structure (DVM-UBC) to describe the behavior of a stand-alone tidal-current turbine and its surrounding unsteady flow and develop a numerical model to predict the performance and wake structure of the turbine based on DVM-UBC. To validate this method, we conducted a series of towing tank tests. DVM-UBC is then validated with several kinematic and dynamic results. When we compared the results obtained with DVM-UBC with our towing tank test results, published results, and the results obtained with other numerical methods, we achieved good agreements. Our comparisons also suggested that DVM-UBC can predict the performance of a turbine 50% more accurately than the traditional discrete-vortex method (traditional DVM) with comparable computational effort and will produce results comparable to the Reynolds averaged Navier–Stokes equation with much less computational effort.

FIGURES IN THIS ARTICLE
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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

An illustration of turbine working principle. (This illustration does not represent the configuration and the scale of a real turbine. Also, induced velocity is not depicted due to the uncertainty of its direction.)

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Figure 2

An illustration of a three-dimensional time-dependent vortex wake structure

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Figure 3

An illustration of one of the turbines designed at UBC with the mounting frame

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Figure 4

Testing facility of UBC towing tank

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Figure 5

Wake trajectory generated by using DVM-UBC is superimposed on the wake trajectory in Ref. 22

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Figure 6

Comparison of the two-dimensional wake trajectory by using conformal mapping method (24) (gray) and DVM-UBC (black)

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Figure 7

(a) Turbine wake velocity generated by using DVM-UBC; and (b) turbine wake velocity generated by using FLUENT

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Figure 8

A comparison of the power coefficient of a stand-alone tidal-current turbine

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Figure 9

A snapshot of a turbine being tested in UBC towing tank

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Figure 10

A comparison of power coefficient of a stand-alone tidal-current turbine by using different methods (DVM-UBC, traditional DVM, FLUENT , and experiment)

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Figure 11

The relationship between torque and azimuth angle obtained by using different methods under scenario 1 (a) and scenario 2 (b)

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Figure 12

Blade arm connection

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