Study of the effects of confinement on the performance of the HAO turbine

Olivier Gauvin-Tremblay

Master degree student
olivier.gauvin.2@ulaval.ca

In the development of the oscillating-foils turbine (HAO : hydrolienne à ailes oscillantes), optimal parameters have been found in attempts to reach better efficiencies using CFD models. These CFD simulations took into account the effects of turbulence and have been validated by experimental results. However, they only considered uniform upstream flow without boundary in the neighboring of the turbine. In other words, the oscillating hydrofoil took place in a large area without boundary over and under it. For the past analysis, it was the better way to do it because it allowed focusing on kinematic and geometric parameters, strongly linked with fluid dynamic around the hydrofoil. Now, we now that this representation doesn’t correspond to the real environment in which a hydrokinetic turbine will take place. In fact, a HAO turbine will see its performances modified by the seabed (or riverbed), the free-surface or even by other turbines in its vicinity.

Thus, studies are realised to understand confined flows, especially those of the same type we found around a HAO. Many of their effects are unknown. For instance, since free-surface is capable of transmitting pressure waves and deforming, what is its impact on turbine performances and what is the proportion of energy from the oncoming flow that is loss due to wave generation? In order to answer these questions, it’s necessary to consider the main aspects of the flow, namely turbulence, boundary proximity, gravity and 3D effects.

Following this research, tools that will have been developed can be used to predict optimal operation depth, to know the influence of a particular river topography or to improve the positions of turbines within a tidal farm.