Pivot location and mass ratio effects on flow-induced vibration of a fully passive flapping foil.

This paper reports on an extensive numerical investigation of the effects of pivot location and mass ratio ( m ∗ = solid/fluid mass) on flow-induced vibration (FIV) of a foil undergoing fully passive two-degree-of-freedom (2-DOF) plunging and pitching motion in a two-dimensional free-stream flow. Here, the normalised pivot location is defined by x = x p ∕ c , with c the foil length and x p the distance to the foil leading edge. A comprehensive set of numerical simulations were conducted employing an Immersed Boundary Method at a Reynolds number of 400. By analysing the FIV dynamics for three selected mass ratios, m ∗ = 5 , 20 and 200, at two pivot locations, x = 0. 35 and 0.50, it is found that there are two types (type-I and type-II) of FIV responses, one is primarily a driven static instability while the other is strongly associated with vortex shedding. Interestingly, for x = 0. 50 , which is close to the mass centre, increasing the mass ratio can favour suppression of the chaotic response. Importantly, it is shown that there exists a critical mass ratio, above which the foil oscillations are suddenly suppressed. The findings indicate that the combined effects of eccentricity and mass ratio on the foil dynamics can be profound. [ABSTRACT FROM AUTHOR]