# Experimental and Numerical investigation of Vortex induced vibration for a circular cylinder

## Involved Scientist

Hassan el Sheshtawy M. Sc.

Simon Tödter M. Sc.

Prof. Dr.-Ing. Bettar Ould el Moctar

## Project description

Vortex induced vibration (VIV), the flow around bluff bodies, which may induce substantial structure vibration, comes under a more general category of the fluid structure interaction (FSI) problems. In marine engineering, VIV has many applications such as offshore risers, offshore wind turbine, etc. Resonant conditions may occur if the frequency of the shed vortices matches a natural frequency of the structure. At resonance, oscillation in the transverse direction to the flow may affect the structural integrity and its fatigue life, or damage it. Consequently, VIV is a well-known and extensively investigated phenomenon. However, it is still not understood completely. In this research project the VIV for different circular cylinders are investigated experimentally and numerically.

An experimental investigations of VIV of a partially and a fully submerged monopile structure in model scale is made in the circulation water channel of the university of Duisburg-Essen. The structure and the fluid flow characteristics are measured simultaneously in the experiments. A Digital Image Correlation (DIC) method was used to measure structure response, results obtained by the DIC method are compared with the measurements of a triaxial . A Laser Doppler anemometer (LDV) system was used to measure the vortex shedding frequencies and the velocities of the inlet flow. An accelerometer and a load cell were used to measure the structure vibration and the load due to fluid flow. A Particle image Velocimetry (PIV) system was used to measure the fluid flow characteristics and visualize the wakes and eddies behind the different cylinder oscillations. All the experimental setups are shown in figure 1. Figure 2 shows some results from our experiment at U = 1.8 m/s, corresponding to reduced velocity, U_{r} = 5.832, corresponding to Re = 56520).

Two function objects were implemented into OpenFoam, an opensource C++ library for CFD, able to compute fluid structure interaction for 2D-circular cylinder oscillate in one and two degrees of freedom. The function object was coupled with an incompressible flow solver, which is able to compute laminar flows as well as turbulent flows. Applying this function object, we investigated the fluid structure interaction of a low mass ration cylinder (the ratio between the mass and the displaced fluid). In addition, the OpenFOAM-FSI solver was used to solve 3D-circular cylinder oscillate in two degrees of freedom. The solver is based completely on the finite volume method, and both the fluid and solid were solved in the same solver based on the arbitrary Lagrangian-Eulerian (ALE) mapping equations approach. The results are compared to the experimental results and with another commercial software ‘Star-CCM+’

## Sample results

Video 1: Spatially resolved deflection of a partially submerged cylinder measured with DIC at a speed of U = 1.62 m / s. Here the Z-axis is the horizontal axis normal to the direction of flow [2].

## Publications

- Tödter, S., el Sheshtawy, H., Neugebauer, J., el Moctar, O., & Schellin, T. E. (2021).

**Deformation measurement of a monopile subject to vortex-induced vibration using digital image correlation.**

Ocean Engineering, 221, 108548. - El Shehstawy, H., Changqing, J., el Moctar, O., Schellin, T.E., 2021.

**Numerical investigation of a tidal stream turbine,**

Journal of ships and offshore structure, under review. - El Shehstawy, H., el Moctar, 2021.

**Fluid Structure Interaction Investigation of a Circular Cylinder in a Low Reynolds Number,**

Journal of ships and offshore structure, under review. - El Sheshtawy, H., Tödter, S., Neugebauer, J., el Moctar, O., & Schellin, T.E.

**Experimental benchmark test cases for Vortex induced vibration of a circular cylinder oscillate in two degrees of freedom, under review**. - El Sheshtawy, H., Youssef, M., Tödter, S., Neugebauer, J., el Moctar, O., & Schellin, T.E.

**Experimental and Numerical Investigation of Vortex-Induced Vibration for a Fully Submerged Oscillating Circular Cylinder in a Circulating Water Channel., ISOPE Accepted.** - Youssef, M., el Moctar, O., El Sheshtawy, H., Tödter, S., Neugebauer, J., el Moctar, O., & Schellin, T.E.

**Experimental Investigation to Suppress Vortex-Induced Vibration of a Flexible Circular Cylinder., under review.** - El Sheshtawy, H., Tödter, S., Neugebauer, J., el Moctar, O., & Schellin, T.E.

**PIV measurement of vortex induced vibration of a circular cylinder oscillating in two degrees of freedom., under review.** - Tödter, S., El Shehstawy, H., Neugebauer, J., el Moctar, O., 2019.

**Experimental Investigation of Vortex-Induced Vibrations Using 3D-Accelerometry and Digital Image Correlation,**

International Workshop on Ship and Marine Hydrodynamic. - El Shehstawy, H., Changqing, J., el Moctar, O., 2019.

**Fluid Structure Interaction Investigation of a Circular Cylinder in a Low Reynolds Number.**

14th OpenFOAM Workshop 2019. - Tödter, S., El Shehstawy, H., Neugebauer, J., el Moctar, O., 2019.

**Deformation Measurement of a Pipe Subjected to Vortex Induced Vibration Using Digital Image Correlation.**

Conference Paper, The Sixth International Conference on Advanced Model Measurement Technology for The Maritime Industry.

## Project duration: 2018 - Funding

Institute for Ship Technology,

Marine Technology and Transport Systems

at the University of Duisburg-Essen