Abstract
This Round Robin Test program aims to establish the influence of the combined wave and current effect on the power capture and performance of a generic tidal turbine prototype. Three facilities offering similar range of experimental conditions have been selected on the basis that their dimensions along with the rotor diameter of the turbine translate into low blockage ratio conditions. The performance of the turbine shows differences between the facilities up to 25% in terms of average power coefficient, depending on the wave and current cases. To prevent the flow velocity increasing these differences, the turbine performance coefficients have been systematically normalized using a time-average disc-integrated velocity, accounting for vertical gradients over the turbine swept area. Differences linked to blockage effects and turbulence characteristics between facilities are both responsible for 5 to 10% of the power coefficient gaps. The intrinsic differences between the tanks play a significant role as well. A first attempt is given to show how the wave-current interaction effects can be responsible for differences in the turbine performance. In these tanks, the simultaneous generation of wave and current is a key part often producing disruptions in both of these flow characteristics.
Highlights
Prototype testing is an integral part of the development process for many technologies
In the case of the performance evaluation of marine energy converters, the test environment may refer to facilities involving flume or tow tanks and the appliance usually refers to the converter and the instrumentation equipment to measure the variables of interest; for example, power, loads, and so forth
Results obtained at IFREMER are different from those measured at FLOWAVE or CNR-INM—average and standard-deviation of the amplitude of the Hilbert transform are larger compared to the other tanks
Summary
Prototype testing is an integral part of the development process for many technologies. One of the main disadvantages associated with experimental research is related to the existence of side effects which could potentially lead to an inadequate interpretation of results These uncertainties may be related to random or systematic errors which involve the test environment or the appliance. A Round Robin Test (RRT) can be designed to enable a first stage quantification of a facility’s impact on the technology being tested and on the quality of the tests results. These results are obtained with the same testing program being repeatedly undertaken on the same device model and at a number of test laboratories, as performed by Aubrun et al [1] on porous disc models representing wind turbines. Such tests can be used to evaluate and improve (if necessary) the specifications given in the international standards—IEC TS 62600-200 to 202 [2,3,4], in the ITTC procedures and guidelines [5,6] or in the EquiMar protocols [7] for instance, as explained by Germain et al [8,9]
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