Numerial Study of Vortex-Induced Vibration of Circular Cylinder Adjacent to Plane Boundary Using Direct-Forcing Immersed Boundary Method

Abstract

Vortex-induced vibration (VIV) is an important physical phenomenon as one design a riser or a cylindrical structure in ocean. As the riser or the cylindrical structure is adjacent to a seabed, the boundary effect on VIV is not fully understood yet. The direct-forcing immersed boundary (DFIB) method is used to investigate a two-degree-of-freedom VIV of a flexible supported circular cylinder adjacent to a plane boundary in this study. Furthermore, the effect of the VIV of cylinder on skin friction of the plane boundary is investigated. The effects of varying reduced velocity and gap ratio on VIV are discussed. Only a single vortex street is found when the cylinder is close to plane boundary. Hydrodynamic coefficients of the freely vibrating cylinder are analyzed in time and spectral domains. Furthermore, nearly round oval-shaped motion is observed as the so-called lock-in phenomenon occurs. The skin friction of the plane boundary is predicted by the DFIB model. Results show that the vibrating cylinder in the boundary layer flow can reduce the friction effectively. This proposed DFIB model can be useful for the investigation of VIV of the structures under the plane boundary effect even for a small gap between the cylinder and the boundary.

Experimental investigation on vortex-induced vibration and solid-structure impact of a near-bottom horizontal flexible pipeline in oblique shear flow

“…Chen et al (2019) reported that the cylinder partially submerged in the boundary layer exhibits a prolonged initial branch followed by a lower branch. In contrast to a typical figure-eight orbit of wall-free cylinders, a round oval-shaped motion was observed by Chern et al (2017) They subsequently reported the onset flow velocity for such a mode transition which was increased with decreasing G/D (Li et al, 2013).…”

Numerical modeling of flow past a volumeless and thin rigid body using direct forcing immersed boundary method

“…The current numerical method has been effectively applied to a range of problems involving thick rigid structures, such as circular cylinders, airfoils, and spherical solid objects, in past studies. [21][22][23][24][25][26]…”

“…The subgrid technique can also be used for solid–fluid boundary interface cells (cut cells) to refine the geometry of the solid body and calculate the fraction efficiently. This type of DFIB approach has been developed and used successfully in many studies 20‐26 . This is also referred to as the one‐stage direct‐forcing IB method.…”

“…This type of DFIB approach has been developed and used successfully in many studies. [20][21][22][23][24][25][26] This is also referred to as the one-stage direct-forcing IB method. Furthermore, the virtual force term in the one-stage DFIB projection method revises the velocity field near the solid region but not the pressure at the end of each time step.…”