Session: 08-06-01 Internal Flows & FIV

Paper Number: 103416

103416 - Numerical Investigation of Internal Flow Effect on the Cross-Flow Vortex-Induced Vibration 

As ocean recourse exploration expands into deep waters, the flexibility of a marine riser is significantly enhanced due to the increased aspect ratio, IFE (Internal Flow Effect) becomes remarkable inevitably, especially when the internal flow has a large density in the exploitation of marine metal resources. This study is motivated to examine the IFE on the CF (Cross-Flow) VIV (Vortex-Induced Vibration) of flexible marine risers. The dynamic equations of a flexible riser subjected to a uniform current are established based on Hamilton Principle employing a semi-empirical hydrodynamic force model. The governing equations can be discretized by finite element method and solved by Newmark-Beta method. A MATLAB code is developed, and the convergence is confirmed by increasing node number and decreasing the time step-size. The code has been validated for IFE and VIV respectively. The critical internal flow velocities are calculated at different internal flow densities at first. Then, the VIV responses of a flexible riser at different subcritical internal flow velocities, internal flow densities and current velocities are studied. The results have demonstrated that with the increase of internal flow velocity and density, the dominant mode can transfer to a higher order, accompanied by a jump increase of the  dominant frequency. The increase or decrease of RMS(root mean square) displacement at different internal flow depends on whether the VIV dominant frequency approaches or departs from the vortex shedding frequency. This study can be provided as a workbench for further investigations.

Presenting Author: Guixin Zhao Shanghai Jiao Tong University

Presenting Author Biography: Guixin Zhao(1996-), Female, Ph.D. Candidate
School of Naval Architecture, Ocean and Civil Engineering
Shanghai Jiao Tong University
Shanghai, P. R. China
tel: +86 17862703365
email:zhaoguixin@sjtu.edu.cn

Authors:

Guixin Zhao Shanghai Jiao Tong University
Shuai Meng Shanghai Jiao Tong University