a b s t r a c tThe present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied.

An array of horizontal axis Savonius-type three-part rotors, each consisting of three blades, is designed and built in-house to conduct performance analysis experiments for a parallel tandem arrangement in a wave flume at different wave physical and positioning conditions. The experiments are performed at different wave heights, wave periods, and longitudinal spacings between the rotors, and their submergence positions are for a previously adjusted constant water depth. The power output and wave-to-mechanical energy conversion efficiency of the "first rotor," only in a singleand three-rotor array arrangement, is comparatively studied both qualitatively and quantitatively to determine the optimum centre-to-centre spacing between the rotors as well as the wave physical characteristics at intermediate-to-shallow water depths. It is found that a higher rotational speed can be attained at a higher wave height, centreto-centre rotor spacing and/or wave period until the water wave overtops or breaks down at larger wave periods. A submergence level that is very close to the water's surface is also found to have a positive influence on the rotor performance, while a positive submergence level has a negative effect. The present study suggests that experimental solutions within the wave-current flume can provide a proper guideline for the performance analysis of such device(s) for further studies of the optimization of the design of Savonius type multi-rotor arrays under different operating conditions, if suitable geometry dimensioning, i.e., scaling issues, submergence positioning, rotor spacing, and physical flow conditions, are provided in accordance with the existing water depth. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4938146] 063125-2 M. Tutar and I. Veci J. Renewable Sustainable Energy 7, 063125 (2015) 063125-5 M. Tutar and I. Veci J. Renewable Sustainable Energy 7, 063125 (2015) 063125-6 M. Tutar and I. Veci J. Renewable Sustainable Energy 7, 063125 (2015) 063125-12 M. Tutar and I. Veci J. Renewable Sustainable Energy 7, 063125 (2015)

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