Analysis of vortex induced vibration on an offshore structure using a coupled FSI solver

Abstract

Fluid structure Interaction (FSI) is one of the emerging fields in numerical simulation and calculation of multi-physics problems. FSI becomes crucial in capturing large deformations in offshore structures and these deformations are caused by the vortex induced loads. FSI imposes various challenges due to its complexity in nature of interaction between a fluid and solid geometries and requirements of computational resources. In this paper, FSI analysis is conducted on a cylindrical member which may be considered as a leg of an offshore platform. The FSI analysis is performed using the commercial package ANSYS 14.0. The simulation of vortex induced loads with FSI is highly mesh dependent, so many cases were simulated for obtaining an optimum grid size. Computational Fluid Dynamics (CFD) analysis of a two dimensional model have been performed and the obtained results were validated with the literature studies. CFD analysis is performed on the extruded version of the two dimensional mesh and the results were compared with the previously obtained two dimensional results. Preliminary FSI analysis is done by coupling the structural and fluid solvers together at smaller time steps and the dynamic response of the structural member to the periodically varying Vortex induced vibrations (VIV) loads were observed and studied.