Numerical Simulation of an Ocean Current Turbine Operating in a Wake Field

An Ocean Current Turbine (OCT) numerical simulation for creating, testing and
tuning flight and power takeoff controllers, as well as for farm layout optimization is
presented. This simulation utilizes a novel approach for analytically describing oceanic
turbulence. This approach has been integrated into a previously developed turbine
simulation that uses unsteady Blade Element Momentum theory. Using this, the
dynamical response and power production of a single OCT operating in ambient
turbulence is quantified.
An approach for integrating wake effects into this single device numerical
simulation is presented for predicting OCT performance within a farm. To accomplish
this, far wake characteristics behind a turbine are numerically described using analytic
expressions derived from wind turbine wake models. These expressions are tuned to
match OCT wake characteristics calculated from CFD analyses and experimental data. Turbine wake is characterized in terms of increased turbulence intensities and decreased
mean wake velocities. These parameters are calculated based on the performance of the
upstream OCT and integrated into the environmental models used by downstream OCT.
Simulation results are presented that quantify the effects of wakes on downstream turbine
performance over a wide range of relative downstream and cross stream locations for
both moored and bottom mounted turbine systems. This is done to enable the
development and testing of flight and power takeoff controllers designed for maximizing
energy production and reduce turbine loadings.