A study of two-dimensional flow past an oscillating cylinder

Abstract

In this paper we describe a detailed study of the wake structures and flow dynamics associated with simulated two-dimensional flows past a circular cylinder that is either stationary or in simple harmonic cross-flow oscillation. Results are examined for Re = 500 and a fixed motion amplitude of y max /D = 0.25. The study concentrates on a domain of oscillation frequencies near the natural shedding frequency of the fixed cylinder. In addition to the change in phase of vortex shedding with respect to cylinder motion observed in previous experimental studies, we note a central band of frequencies for which the wake exhibits long-time-scale relaxation oscillator behaviour. Time-periodic states with asymmetric wake structures and non-zero mean lift were also observed for oscillation frequencies near the lower edge of the relaxation oscillator band. In this regime we compute a number of bifurcations between different wake configurations and show that the flow state is not a unique function of the oscillation frequency. Results are interpreted using an analysis of vorticity generation and transport in the base region of the cylinder. We suggest that the dynamics of the change in phase of shedding arise from a competition between two different mechanisms of vorticity production.

High Reynolds number oscillations of a circular cylinder

“…Dalton and Chantranuvatana (1980) thus explaining some features of the near field flow. Blackburn and Henderson (1999) in their numerical simulations concentrated their attention to the flow at Re = 500 and the amplitude ratio 0.25 in order to study the effect of variations in frequency ratio on the entrainment phenomena produced by forced cross-flow oscillation within the primary synchronization regime. The work of deals with the numerical simulations of the flow past over an oscillating cylinder; they used a hybrid vortex method in their simulations and kept the Reynolds number with a low value.…”

Streamwise forced oscillations of circular and square cylinders

“…Streamwise forcing is just one method of active open-loop flow control that can be employed on the cylinder wake. Others include, but are not limited to, transverse (cross-stream) oscillation, [1][2][3][4] rotational oscillation of the cylinder, [5][6][7][8] constant rotation of the cylinder, 9,10 and actuation by synthetic jets from the surface of the cylinder and base bleed. [11][12][13] Previous studies of streamwise forced oscillation [14][15][16][17] have investigated the synchronization between the forcing and the vortex shedding.…”

On the use of matrix-free shift-invert strategies for global flow instability analysis

“…Finally time integration employs a backwardstime differencing scheme described by Karniadakis et al [10]. This code has been validated and used in a number of works, see [4,5]. A representative selection of these problems is employed as validation cases in Section 4.…”