Author(s): Vesselina Roussinova; Haonan Kong; Vesselin Stoilov

Linked Author(s): Vesselina Roussinova, Vesselin Stoilov

Keywords: VIV; Elastic cylinder; Shallow flow; FSI

Abstract: In this paper, two degree-of-freedom vortex induced vibration (VIV) of a circular cylinder with diameter D = 0.09 m is studied using a three-dimensional computational fluid dynamics approach. The main objective of this study is to investigate the fluid structure interactions (FSI) on the cross-flow VIV responses and the corresponding characteristics of the flow field in the wake. Besides that, the VIV response at different flow conditions (bulk velocity) is utilized to optimize the hydrokinetic energy extraction. Therefore, the amplitude and frequency of the unsteady oscillation of the cylinder are the two main parameters that need to be optimized. The current fluid-structure interaction problem was solved using the two-way coupled simulations in commercial software ANSYS Fluent V.16. Transient structural and flow simulations are coupled in two-way data transfer controlled by the system coupling. To accommodate the motion of cylinder, the dynamic smoothing and remeshing have been applied. The new mesh configuration is automatically constructed based on the displacement of the cylinder. The detached eddy simulation (DES) turbulence model was selected for flow simulations at high Reynolds number while for low Reynolds number flow conditions, the laminar model was employed. In the transient structural model, the cylinder has displacement constrains in the streamwise (x) and transverse (z) directions, while the cross-flow (y) direction is free to oscillate. Elastic support is applied on the surface of the cylinder and the model also account for the buoyancy and gravitational force. The grid independence of the fluid solution is verified for the case of the stationary rigid cylinder for each flow condition. The fine grid was selected for the FSI simulation of the elastic cylinder. The FSI simulation has duration of 8 s and time step dt = 0.025 s.The inline and cross-flow response amplitude ratios (Ax/D, Ay/D) are obtained and analyzed as a function of time. The fluctuating lift and drag coefficients are also calculated. A significant increase of the vibration amplitudes is observed with the increase of the bulk velocity, leading to the overall increase of the projected power output. The inline and cross-flow VIV response frequencies are also found to increase. Detailed validation and analysis of the simulation result will be presented in the full paper.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022564

Year: 2022