FLOW-INDUCED VIBRATIONS OF A SQUARE CYLINDER WITH RIGID UPSTREAM SPLITTER PLATE

Flow across geometries of non-circular cross-section is encountered in many applications such as buildings and offshore semi-submersible columns. In particular, columns of semi-submersibles with square cross-section are subjected to complex ocean currents which could lead to flow-induced vibrations. The possibilities of resonance-type response (vortex-induced vibrations) along with motion-induced instability-type response (galloping) has been observed for such cases, which could be detrimental to the structural integrity. Therefore, it is imperative to control these unwanted oscillations. One possibility is the introduction of a rigid splitter plate on the upstream side of the structure, which has been found to suppress vibrations in case of a circular cross-section. The current study aims to explore this effect by considering a splitter plate of length equal to the side of a square cylinder. A two-dimensional stabilized Petrov-Galerkin variational formulation is utilized to solve the Navier-Stokes equations on an arbitrary Lagrangian-Eulerian moving mesh framework. The rigid cylinder is elastically mounted on a spring and is free to oscillate in the cross-flow direction. The gap between the cylinder and the trailing edge of the splitter plate is varied in the range of 0 to 3D, with D being the side of the cylinder. The study is conducted at Reynolds number of 200 and a mass ratio of 10 in which the galloping-type of instabilities are expected. The results may pave the way for possible passive suppression of flow-induced vibrations for marine structures with square cross-section.