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# Flow unsteadiness and stability characteristics of low-Re flow past an inclined triangular cylinder

[+] Author and Article Information
Wei Zhang

Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China
zhangwei@zstu.edu.cn

Hui Yang

Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China
yanghui@zstu.edu.cn

Hua-Shu Dou

Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China
huashudou@yahoo.com

Zuchao Zhu

Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China
zhuzuchao@zstu.edu.cn

1Corresponding author.

ASME doi:10.1115/1.4037277 History: Received February 16, 2017; Revised June 16, 2017

## Abstract

The present study investigates the two-dimensional flow past an inclined triangular cylinder at $Re=100$. Numerical simulation is performed to explore the effect of cylinder inclination on the aerodynamic quantities, unsteady flow patterns, time-averaged flow characteristics and flow unsteadiness. We also provide the first global linear stability analysis and sensitivity analysis on the targeted physical problem for the potential application of flow control. The objective of this work is to quantitatively identify the effect of cylinder inclination on the characteristic quantities and unsteady flow patterns, with emphasis on the flow unsteadiness and instability. Numerical results reveal that the flow unsteadiness is generally more pronounced for the base-facing-like cylinders ($\alpha\to60^\circ$) where separation occurs at the front corners. The inclined cylinder reduces the velocity deficiency in the near-wake, and the reduction in far-wake is the most notable for the $\alpha=30^\circ$ cylinder. The transverse distributions of several quantities are shifted towards the negative \textit{y}-direction, such as the maximum velocity deficiency and maximum/minimum velocity fluctuation. Finally, the global stability and sensitivity analysis show that the spatial structures of perturbed velocities are quite similar for $\alpha\le30^\circ$ and the temporal growth rate of perturbation is sensitive to the near-wake flow, while for $\alpha\ge40^\circ$ there are remarkable transverse expansion and streamwise elongation of the perturbed velocities and the growth rate is sensitive to the far-wake flow.

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