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Numerical study of cross flow water turbines arrangements

Date: November 01, 2013 at 11:24 GMT

The HARVEST (Hydrolienne à Axe de Rotation Vertical Stabilisé) project aims to develop a cross flow water turbine concept for marine current energy conversion. When the axis of rotation is vertical, these turbines have the obvious advantage of working whatever the flow direction. The drawback is that there are less efficient than their horizontal counterpart when considered alone for free stream conditions.
Thus, the present study investigates the efficiency of several vertical axis turbines configurations, specific to the technology, which could represent future hydropower installations. First, a single turbine in an unbounded domain is considered. Simulations are carried out with a code which couples a Navier-Stokes computation of the flow with a macroscopic description of the turbine. The effect of the blades on the flow are modeled by time averaged source terms in the momentum equations. The method is validated with experimental results of a Darrieus wind turbine and is then applied for the description of hydraulic turbines.
Then, the effect of piling up several turbines on the same axis of rotation to make a tower is investigated. We demonstrate that not only is this profitable because only one alternator is needed but the average efficiency of the configuration is also increased because of the tower shape. The tower is then inserted into a cluster of several
lined up towers which makes a barge. Simulations show that the average barge efficiency rises as the distance between towers is decreased and as the number of towers in increased within the row. Thereby, the efficiency of a single isolated turbine is greatly increased when set both into a tower and into a cluster of several towers. 

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