Title: Vortex dislocation characteristics of a dual-step cylinder in low-Re flow

Authors: Chunning Ji; Xiaoxiao Yang; Yuting Cui; Weilin Chen

Addresses: State Key Laboratory of Hydraulic Engineering Simulation and Safety, Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience of China Earthquake Administration, Tianjin University, Tianjin 300350, China ' School of Civil Engineering, Tianjin University, Tianjin 300350, China ' School of Civil Engineering, Tianjin University, Tianjin 300350, China ' School of Civil Engineering, Tianjin University, Tianjin 300350, China

Abstract: Flow around a dual step cylinder for D/d = 2 and L/D = 5 at a low Reynolds number of Re_D = 200 is numerically investigated utilising the immersed boundary method. The vortex dislocation caused by two steps is investigated. It was found that a pair of streamwise vortex - the centre vortex exists at the downstream of the large cylinder. Meanwhile, due to the barrier effect of the centre vortices, a very weak L-cell exists behind the centre of the large cylinder. In a complete dislocation cycle, three positive and negative half-loop connections appear alternately. This cycle is related not only to the phase realignment of the different vortex cells, but also to the connection realignment. Moreover, the lateral velocity is always dominated by the vortex shedding frequency. While in the streamwise velocity spectra, the vortex shedding frequency gradually dissipates in the downstream, leaving lower frequencies of dislocation.

Keywords: vortex dislocation; dual-step cylinder; wake; low-Re flow.

DOI: 10.1504/IJCAT.2020.107428

International Journal of Computer Applications in Technology, 2020 Vol.62 No.4, pp.307 - 317

Received: 19 Sep 2019
Accepted: 19 Nov 2019
Published online: 28 May 2020 *

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