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a b s t r a c tThis study proposes an innovative turbine that consists of a vertical flat plate, which is allowed to rotate freely about a vertical axis of symmetry and exploits the autorotation phenomenon to harvest the energy from the current. This system is called here Vertical Axis Autorotation Current Turbine (VAACT). The VAACT utilizes the extra mass moment of inertia to improve the rotational quality which is state of the art in this turbine. This paper covers the principle behind the VAACT and outlines procedures and results for experiments proving the basic feasibility. Also, the operation of the turbine will be discussed by experimental results of the torque coefficient, performance and kinematic parameters. Tests were conducted in LOC (Laboratory of Wave and Current) at COPPE/Federal University of Rio de Janeiro (COPPE/ UFRJ).Utilizing the extra mass moment of inertia on the VAACT causes to extract the energy as an efficient turbine in very low head current. The maximum VAACT efficiency has been obtained experimentally in optimum non-dimensional moment of inertia in range of 0.5 and 0.6.

This study examines the efficiency of a vertical axis current turbine (VACT) according to various non-dimensional mass moments of inertia. The vertical axis current turbine of drag force type with flat plate-shaped blade is tested. From experiments in a circulating water channel the angular velocity, the power coefficient and tip speed ratio of the vertical axis current turbine are obtained. The property changes for various conditions give the relationships between efficiency-related parameters. The maximum power coefficients of experiments occur at the tip speed ratio of approximately 0.35∼0.40. From the experiments, turbine is found to give a 7% power coefficient which related to I* = 0.52.

In this paper, effects of flight distance from ground surface and the thickness of the airfoils moving at ground proximity on the inception point of the transition phenomenon, the start of flow separation, and the boundary layer thickness have been analyzed. The amounts of drag force as well as the lift of the airfoil in viscous flows are influenced by these parameters. Included in this study are the effects of change in Reynolds number and angle of attack on the symmetric airfoils which are carefully investigated. Results of this aerodynamic analysis indicate that the motion at ground proximity is the cause of some changes in boundary layer properties. By close scrutiny of these changes; justifications are found for the behavior of the lift and drag forces at ground proximity.

This paper outlines the results for a set of experiments carried out on Vertical Axis Autorotation Current Turbine (VAACT) which is an innovative concept among the other lowhead hydrokinetic energy converters. The VAACT is a one degree of freedom hinged plate which utilizes the autorotation phenomenon to rotate about its vertical axis in uniform water current. The state of the art on this turbine is application of the extra moment of inertia and also flapped shape of the rotor blade to improve the autorotation characteristics as the principle of operation of the turbine. Investigation of the effect of the extra moment of inertia and the flap on the operational characteristics such as maximum attainable angular velocity and tip speed ratio, obtainable torque of the turbine and its performance is the main objective of this paper. The VAACT harvests energy efficiently from very low head current. The performance of the flapped configuration of this turbine reaches up to 33 percent in the very low current velocity. The highest efficiencies occur in the range of 0.65 to 0.85 of tip speed ratio and also in the range of 0.6 to 0.7 of the non-dimensional moment of inertia. Furthermore, this study has shown that the flap increases the power coefficient significantly by a factor of up to 5 compared to flat plate type.