Investigation of the Vortex-Induced Transverse Vibration of Cylinders Near a Plane Wall with the Local Domain-Free Discretization Method

Abstract

The vortex-induced vibration of a circular cylinder and two inline circular cylinders near a plane wall at a Reynolds number of 150 is numerically investigated by using a self-developed immersed boundary method called the local domain-free discretization (DFD) method. The cylinders are elastically mounted with a mass ratio of 8/π and a 0 damping ratio and can only vibrate in the transverse direction. The reduced velocity varies from 2 to 9, with an interval of 1. Three gaps, e=0.1D, 1D, and 2D (D is the cylinder diameter), are investigated for the case of an isolated cylinder and two inline cylinders while the center-to-center spacing (L) is 1.5D for the two-inline-cylinders case. A model for the collision of the cylinders with the wall is adopted in which the bouncing back is forced when the gap between the cylinder and the plane wall is smaller than 0.02D. It is observed that the existence of the plane wall significantly affects the cylinder response both in the one-isolated-cylinder and two-inline-cylinders cases. The features, including vibration amplitudes, frequencies, fluid forces, the maximal or minimal gap between the cylinder bottom and the plane wall, and the vortex shedding patterns, are explored in detail. Interactions between the front and rear cylinders and differences between the one-isolated-cylinder and two-inline-cylinders cases are discussed. The research has immense significance for the design of near-wall cylindrical structures, such as the deep-water pipeline system on the seafloor.

Keywords

• vortex-induced vibration
• circular cylinder
• tandem arrangement
• wall proximity
• domain-free discretization