Path curvature enhances the flow-induced vibrations of a cylinder without structural restoring force

Abstract

A cylinder immersed in a current and free to translate along a circular arc is considered to investigate the impact of path curvature on the flow-induced vibrations (FIV) occurring without structural restoring force. Path curvature magnitude ( $\kappa$ , inverse of path radius non-dimensionalized by the body diameter $D$ ) is varied from $0$ (transverse rectilinear path) to $20$ , over a wide range of values of the structure to displaced fluid mass ratio, $m^\star \in [0.05,10]$ . The exploration is carried out numerically at subcritical and postcritical values of the Reynolds number ( $Re$ , based on $D$ and the inflow velocity), i.e. below and above the critical value $47$ for the onset of flow unsteadiness when the body is fixed, up to $100$ . Path curvature triggers a desynchronized regime of the flow–body system in addition to the synchronized regime typical of vortex-induced vibrations, and alters the composition of fluid forcing. The most prominent effect uncovered here is, however, a global enhancement of FIV, with three principal results: (i) vibrations and flow unsteadiness are found to arise at lower subcritical $Re$ along a curved path, down to $19.5$ versus $31$ for $\kappa =0$ ; (ii) the $m^\star$ range where substantial responses develop is considerably extended and encompasses the entire interval under study, which contrasts with the narrow band of low $m^\star$ identified for $\kappa =0$ ; (iii) the vibrations are amplified, $+45\,\%$ relative to the peak amplitude measured along a rectilinear path at $Re =100$ .