Power Output of Spring-Mounted Lifting Plates in a Cross Flow

In this paper, a twin cantilever system is spring-mounted on a bearing and investigated experimentally in a cross flow in a wind tunnel; two types of bearing are used, cylindrical with one degree of freedom and spherical with three. By comparing the two systems, it is found that the spherical bearing system is slightly more unstable and operates at a higher oscillation frequency, hence having more favourable conditions for energy harvesting. The physical manifestation of the destabilising effect of the spherical bearing is seen in the yawing figure-of-eight forward and backward motion of the cantilevers about the mount, which can be observed by looking directly down on the set-up. For the range of spring stiffnesses used in this investigation, the power producing capabilities of both systems continue to increase as system natural frequency reaches higher values.