Experimental investigation of flow induced motion and energy conversion for triangular prism

Abstract

Previous studies proved that the triangular prism would go into galloping branch with high amplitude and low frequency. In order to evaluate the energy conversion capacity, a series experiments of flow induced motion (FIM) for triangular prism with physical springs are conducted in the Reynolds number range of 29,559 ≤ Re ≤ 119,376 by varying load resistance, stiffness, mass ratio and aspect ratio. Selective aspect ratios are applied to enhance the hydrokinetic energy captured by the generator. A physical model is used to control the change of load resistance and spring stiffness for a fast and precise oscillator modeling. The analysis of oscillation responses and energy conversion are carried out based on the statistical evaluation of displacement time-history and voltage signals. The effects of system stiffness, mass ratio, aspect ratio and load resistance on the active power (Pharn) of the triangular prism are presented and discussed. The main conclusions can be summarized as follows: (1) The best branch of the triangular prism energy conversion is galloping branch. (2) In the tests, the maximum active power Pharn = 23.37 W and the corresponding efficiency ηharn = 5.21%. The maximum energy conversion efficiency ηharn = 6.17% with the corresponding active power Pharn = 2.94 W. (3) With the increase of the stiffness (K) and the reduce of the mass ratio (m*), the Pharn rises up. (4) The higher aspect ratio (α) can be easier self-excited to galloping from the vortex induced vibration (VIV) but has a negative influence on the Pharn of the galloping branch.