This thesis examines methods for designing and analyzing kinetic turbines based on blade element
momentum (BEM) theory and computational
fluid dynamics (CFD). The underlying goal of the
work was to assess the potential augmentation of power production associated with enclosing the
turbine in an expanding duct. Thus, a comparison of the potential performance of ducted and
non-ducted turbines was carried out. This required de ning optimal turbine performance for both
concepts. BEM is the typical tool used for turbine optimization and is very well established in
the context of wind turbine design. BEM was suitable for conventional turbines, but could not
account for the influence of ducts, and no established methodology for designing ducted turbines
could be found in the literature. Thus, methods were established to design and analyze ducted
turbines based on an extended version of BEM (with CFD-derived coe cients), and based on CFD
simulation. Additional complications arise in designing tidal turbines because traditional techniques
for kinetic turbine design have been established for wind turbines, which are similar in their principle
of operation but are driven by flows with inherently different boundary conditions than tidal currents.
The major difference is that tidal flows are bounded by the ocean floor, the water surface and channel
walls. Thus, analytical and CFD-based methods were established to account for the effects of these
boundaries (called blockage effects) on the optimal design and performance of turbines. Additionally,
tidal flows are driven by changes in the water surface height in the ocean and their velocity is limited
by viscous effects. Turbines introduced into a tidal flow increase the total drag in the system and
reduce the total flow in a region (e.g. a tidal channel). An analytical method to account for this was
taken from the eld of tidal resource assessment, and along with the methods to account for ducts
and blockage effects, was incorporated into a rotor optimization framework. It was found that the
non-ducted turbine can produce more power per installed device frontal area and can be operated
to induce a lesser reduction to the flow through a given tidal channel for a given level of power
production. It was also found that by optimizing turbines for array con gurations that occupy a
large portion of the cross sectional area of a given tidal channel (i.e. tidal fences), the per-device
power can be improved signi cantly compared to a sparse-array scenario. For turbines occupying
50% of a channel cross section, the predicted power improves is by a factor of three. Thus, it has
been recommended that future work focus on analyzing such a strategy in more detail. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3801 |
| Date | 11 January 2012 |
| Creators | Shives, Michael Robert |
| Contributors | Crawford, Curran |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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