CFD Simulation of Vortex Induced Motion of a Caisson during Installation Process

Abstract

This paper presents the CFD investigation of the vortex induced motion (VIM) of a caisson model during the installation process. The simulations were performed by solving the unsteady 3D Navier-Stokes equation. The Dynamic Fluid-Body Interaction (DFBI) tool is utilized to simulate the motions. Typical draft conditions of a caisson during installation process are considered. The present methodology is verified through the free decay and the VIM of a cylinder simulations in two-dimension. Free decay simulations show that the natural frequency decrease with the increasing draft of the caisson. Maximum response amplitudes occur in the range of 10<Vr <13 for the draft Dp=0.1m. The resonance occurs when the crossflow response frequency f y is very close to the natural frequency f n. The inline/crossflow response frequency increases as the draft increases at the same reduced velocity V r. The response frequency in the inline direction is double of that in the crossflow direction. Eight-shaped trajectories are observed. The maximum displacements in the crossflow direction increase as the drafts increase.