We are thankful to be welcome on these lands in friendship. The lands we are situated on are covered by the Williams Treaties and are the traditional territory of the Mississaugas, a branch of the greater Anishinaabeg Nation, including Algonquin, Ojibway, Odawa and Pottawatomi. These lands remain home to many Indigenous nations and peoples.

We acknowledge this land out of respect for the Indigenous nations who have cared for Turtle Island, also called North America, from before the arrival of settler peoples until this day. Most importantly, we acknowledge that the history of these lands has been tainted by poor treatment and a lack of friendship with the First Nations who call them home.

This history is something we are all affected by because we are all treaty people in Canada. We all have a shared history to reflect on, and each of us is affected by this history in different ways. Our past defines our present, but if we move forward as friends and allies, then it does not have to define our future.

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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.