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November 12, 2010

Speaker: Dr. Nicholas Kevlahan, Department of Mathematics & Statistics, McMaster University

Title: The role of vortex wake dynamics in the flow-induced vibration of tube arrays

Abstract: Potential flow and two-dimensional Navier-Stokes calculations are used to investigate the role of vortex shedding in the non-resonant flow-induced vibration of periodic tube arrays. The negative damping theory is shown to be inconsistent with the Navier-Stokes simulations, and allowing only a single degree of freedom in the Navier-Stokes simulations significantly overestimates the critical velocity. In contrast, Navier-Stokes simulations which allow all tubes to move in both the transverse and streamwise directions gives results in good agreement with experiment. Somewhat surprisingly, potential flow calculations including an artificial phase lag between fluid force and tube motion give reasonably accurate results for a wide range of phase lags. This may be due to the fact that the most unstable mode at onset appears to be streamwise anti-phase (not whirling), as observed in the potential flow case.

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