Flow-Induced Vibrations of Single and Tandem Square Columns

Abstract

This work reports a set of numerical experiments to understand flow-induced vibrations of the square columns kept in a tandem arrangement. Results on the coupled force and response dynamics are presented for an isolated column and for a pair of square columns in the tandem configuration where downstream column is elastically mounted and free to oscillate in in-line and transverse directions. We assess the combined wake-induced and sharp-corner based galloping effects on the downstream column by comparing with the isolated square column counterpart. It is known that the circular cylinders undergo vortex-induced motion alone whereas motion of a square column is vortex-induced at low Re and galloping at high Re. The simulations are performed by means of a Petrov-Galerkin based finite-element solver using Arbitrary Lagrangian-Eulerian technique to account for the fluid mesh motion. The predicted results of the isolated column agree well with the available numerical results in the literature. The dimensions of the square columns and the domain are set in order to a have total blockage area of 5 %. The effects of reduced velocity on the fluid forces, wake contours, and the phase angles are analyzed. This work is also an attempt to enhance our understanding on the origin of wake-induced vibrations in a tandem arrangement of bluff bodies. In the case of tandem arrangement, upstream vortex shifts the stagnation point on the downstream column to the lower suction region. Thus a larger lift force is observed for the downstream column as compared to a vibrating isolated column. Phase difference between the transverse load and velocity of the downstream column determines the extent of upstream wake interaction with downstream column. When the column velocity is in-phase with the transverse pressure load component, interaction of wake vortex with the downstream column is minimum. For higher reduced velocities (Ur > 15), the wake downstream is very wide and irregular and the phase angle is consistently close to 180°.

Flow-induced vibration of two tandem square cylinders at low Reynolds number: transitions among vortex-induced vibration, biased oscillation and galloping

“…The existing studies on FIVs of two tandem square cylinders are summarized in table 1. So far, most of the existing studies on FIVs of two tandem cylinders have been concerned with the scenario where the upstream cylinder is fixed (Zhao et al 2015;Jaiman, Pillalamarri & Zhao 2016;Bhatt & Alam 2018;Han et al 2018;Yao & Jaiman 2019;Tamimi et al 2020). It was found that the wake of the upstream cylinder has a significant effect on the response of the downstream cylinder.…”

“…It was found that the wake of the upstream cylinder has a significant effect on the response of the downstream cylinder. For example, Zhao et al (2015) found that the shift of the stagnation point on the downstream cylinder, induced by the vortex shedding from the upstream cylinder, is responsible for the large-amplitude vibration of the downstream cylinder. Bhatt & Alam (2018) affirmed the significant role that the gap flow played in the vibration response of the downstream cylinder.…”