Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Numerical study of flow around a three-dimensional elastic cylinder
based on coupled CFD-FEM method
Wenjie Zhang1, Jianhua Wang1*, Yi Liu2, Hao Guo2, Decheng Wan1
1. Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean andCivil Engineering, Shanghai Jiao Tong University, Shanghai, China
2. Marine Design and Research Institute of China, Shanghai, China* Corresponding Author

upstream of open channel cylinders (Chen, 2016, Yang, 2019). Nikolaos
has studied the physical characteristics of turbulent separation near thevertical intersection of a flat wall and a cylindrical obstacle with bothexperimental and numerical methods (Nikolaos, 2015). This
simplification is feasible for bridge pier structure, but not accurate forslope water movement around vegetation and some other problems.

ABSTRACTIn practical engineering, the long and thin blunt structures are able toproduce non-negligible deformation and periodic vibration under thestrong influence of intense incoming flow. In the present work, a strong
coupling approach is developed based on CFD-FEM method to solve theFSI problem. Fluid field is solved by RANS method with OpenFOAM.
Structural vibration is solved by Newmark-beta method, which is basedon Euler-Bernoulli beam model. Computational mesh updating strategy
is adopted to realize the dynamic mesh updating to consider the effect ofstructural vibration deformation. In this paper, a numerical study of flow
around a three-dimensional elastic cylinder under stokes second orderwave is investigated to validate the developed FSI solver. In order tostudy the wave frequencies effect on the phenomenon of flow aroundelastic cylinders, three different wave frequencies are investigated for athree-dimensional elastic cylinder. Structural response and fluid analysis,i.e., wave profiles and vorticity field are presented. The accuracy andstability of developed CFD-FEM approach are demonstrated through thenumerical studies preliminarily.

The introduction of CFD-FEM provides an effective method to study
cylinder deformation. Bending deformation of a cylinder in single phaseflow has a wide engineering background, among which the typicalapplication is wind resistance of high-rise buildings. Many scholars havecarried out research on both model experiments and numericalsimulations (Waldeck, 1992, Larsen, 1995, Ciesielski, 1996, Facchinetti,2004, Zhang, 2005, Liang, 2019, Francesca, 2021). Similar research
work in two phase flow is relatively rare.
This paper takes an elastic cantilever cylinder model as the research
object. Firstly, the stability of developed FSI solver is preliminarily
verified by grid convergence analysis. The FSI numerical simulations
between waves at different frequencies and fixed elastic cantilever
cylinder are carried out. Both structure vibration displacement responseof elastic cylinder and fluid field characteristics of wave profiles andvorticity field are studied. The research is expected to contribute to theunderstanding of FSI problems.

KEY WORDS: Fluid-structure interaction (FSI), Three-dimensionalelastic cylinder, Vibration deformation, CFD-FEM approach.

INTRODUCTION
THE MATHEMATICAL FORMULATIONS

The model studied in this paper has a wide range of applications in thestudy of sediment dynamics in open channel flow. The model iscommonly used in the research background of riparian water-levelfluctuation zone, erosion ditch, slope water movement around vegetationand so on (Zhang, 1989, Ebrahim, 2018). The structures are generallyregarded as rigid and rigid with no deformation to simplify the research
problems. Many scholars has focused on the horseshoe vortex structure
before the cylinder in open channel flow, and regard the structure
blocking the flow as rigid (Dargahi, 1989, Qi, 2005, Euler, 2012,
Tafarojnoruz, 2010). Chen and Yang have carried out flow experimentson the flow around a cylinder under shallow water in an open channel
flume, and studied the kinematic characteristics of horseshoe vortices

Governing Equations
The flow is assumed as incompressible, and energy transformation
caused by temperature change is ignored. For applications of engineering
problems, the governing equation of the flow field adopts Reynolds
average equation:
ui=0xi

2464(1)