Seiffert, Betsy

This research focused on maximizing the power generated by an array of ocean
current turbines. To achieve this objective, the produced shaft power of an ocean current
turbine (OCT) has been quantified using CFD without adding a duct, as well as over a
range of duct geometries. For an upstream duct, having a diameter 1.6 times the rotor
diameter, the power increased by 8.35% for a duct that extends 1 diameter upstream.
This research also focused on turbine array optimization, providing a
mathematical basis for calculating the water velocity within an array of OCTs. After
developing this wake model, it was validated using experimental data. As the
downstream distance behind the turbine increases, the analytic results become closer to
the experimental results, with a difference of 3% for TI = 3% and difference of 4% for TI
= 15%, both at a downstream distance of 4 rotor diameters.

The influence of monochromatic waves interacting with a submerged bar structure
is investigated through laboratory experiments in a wave flume. Wave profiles for a range
of non-breaking, spilling, and plunging waves were analyzed for three offshore water
depths through the interpretation of wave gauge and video imagery data. Evolution of
propagating waves was reflected in data which showed increased amplitudes due to
shoaling with subsequent breaking, transfer of single frequency spectrum from lower to
higher frequency harmonics, and dissipation of energy after breaking onset. Comparisons
of collected experimental data with previous theory developed by Yao et al (2013), Smith
& Kraus (1991), Galvin (1968) for wave classification showed to be relatively accurate for
both relative submergence and surf similarity methods. Wave breaking onset identified by
instability in the wave crests allowed for measurements of breaking wave height and depth
at breaking. Theory by Johnson (2006) and Goda (1974) compared to experimental data
showed little agreement for predicting breaking wave heights.