Experimental control from wake induced autorotation with applications to energy harvesting

This study is devoted to the investigation of optimal conditions for flow-induced autorotation of a hinged cylinder in a direction perpendicular to the flow in a water tunnel. Previous studies of hinged, immersed cylinders inflow have shown autorotation to be dependent upon the geometric aspects of the body and flow speed when the speed is beyond a critical threshold. Our experiments indicate that introducing a blockage of the appropriate width and at the right distance, upstream of the cylinder, can help induce autorotation, even at much lower flow speeds. Additionally, the percentage of the cylinder’s area blocked (i.e. the blockage ratio), is a significant control parameter, which can be used to manipulate the rotational speed of the cylinder. This phenomenon can be used to generate power which is demonstrated here by a suitable modification of our setup. Our mechanism deviates from traditional wind and hydro-power generators which use blade turbines by considering a cylinder and its modifications as a turbine. Such a design is easy to manufacture and control as is demonstrated in our experiments. Induced autorotation by the introduction of a control body upstream of the turbine is shown to increase power generation in our setup up to 400%.