Author ORCID Identifier

https://orcid.org/0000-0002-0919-6156 : David S.K. Ting

https://orcid.org/0000-0002-3842-0719 : Ran Wang

https://orcid.org/0000-0002-1533-931X : Shaohong Chen

Document Type

Article

Publication Date

10-1-2023

Publication Title

Physics of Fluids

Volume

35

Issue

10

Keywords

Numerical methods, Fluid mechanics, Computational fluid dynamics, Aerodynamics, Flow visualization, Vortex dynamics

Abstract

Unstable motions of bridge stay cables have been observed on site and in wind tunnel tests when a cable is yawed at certain orientations to wind. To uncover the underlying mechanisms, flow around a circular cylinder at a yaw angle of 30° has been numerically analyzed in the current study using delayed detached eddy simulation (DDES) at R e = 10 4 . A comparison with the reference normal flow case indicates the presence of a more coherent span-wise flow structure when the cylinder is yawed at 30°. The application of proper orthogonal decomposition further reveals that at this orientation, a synchronized flow structure exists, which is characterized by continuous anti-symmetric pressure blocks. In addition, a low-frequency flow fluctuation has been identified, the Strouhal number of which is roughly a quarter of that of the conventional Kármán vortex shedding. The pivotal role of axial flow in the intermittent amplification of cylinder sectional lift and the subsequent span-wise propagation of this enhanced local lift event has been revealed. The former is evident from the low-frequency sectional lift peaks occurred during vortex shedding, whereas the propagation speed associated with the latter is in good agreement with the span-wise component of the incoming flow speed. The temporal and spatial impact of axial flow on the surrounding flow structure of the cylinder may serve as a periodic excitation source, which could trigger an unstable response of a cylinder. This, in the context of bridge stay cables, could possibly contribute to the onset mechanism of dry cable galloping.

DOI

10.1063/5.0172648

ISSN

10706631

E-ISSN

10897666

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