Effect of oscillation amplitude on force coefficients of a cylinder oscillated in transverse or in-line directions

Baranyi, László and Daróczy, László (2009) Effect of oscillation amplitude on force coefficients of a cylinder oscillated in transverse or in-line directions. In: Conference on Modelling Fluid Flow CMFF’09. Budapest University of Technology and Economics, Budapest, pp. 323-330. ISBN Vol. I: ISBN 978-963-420-984-3 ö, Vol. II: ISBN 978-963-420-985-0

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Abstract

A finite difference solution is presented for 2D low Reynolds number flow (Re=140 and 160) past a circular cylinder placed in a uniform flow. The cylinder is oscillated mechanically either in-line or transversely under lock-in conditions. Abrupt jumps between two state curves were found for a cylinder oscillated in in-line direction in the time-mean (TM) values of lift and torque coefficients when plotted against amplitude of oscillation. Pre- and post-jump analysis carried out included the investigation of phase angle differences, limit cycles and flow patterns confirming the existence of switches in the vortex structure at certain oscillation amplitude values. The TM of drag and base pressure coefficient and the rms values of all force coefficients were continuous functions of oscillation amplitude. When the cylinder was oscillated transversely to the main stream, however, no jumps were found in the corresponding curves. Here the TM of lift and torque were found to be zero (true also for a stationary cylinder) at all amplitude values. Even though the transverse oscillation breaks the symmetry of the flow, there appears to be symmetry over a period.

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