Berkeley Fluids Seminar

University of California, Berkeley

Bring your lunch and enjoy learning about fluids!

Wednesday, May 4, 2016

240, Bechtel Hall, 13:00-14:00

Dr. Joel Tchoufag (Mechanical Engineering, UC Berkeley)

Endogeneity analysis of path instabilities

Abstract: The dynamical path of buoyancy-driven bodies in a viscous fluid is investigated in a linear stability framework. The departure of falling/rising objects from a straight vertical path can be understood by examining the unstable linear global modes of the fully coupled fluid-solid system linearized around the falling/rising steady state. Although this approach offers a quantitative prediction of the various possible trajectories, it raises new questions about the physical interpretation of fully coupled fluid/solid modes. Are the observed trajectories driven by the fluid dynamics, the solid dynamics, or by their coupling? In which flow regions are those dynamics most active? To answer these questions, we present a straightforward adjoint-based-method that can be used to measure the coupling in any problem where reciprocal interactions between two sub-parts of a system take place. This method is exemplified on the case of a two-dimensional falling ellipse, in the limits of infinitely large and infinitely small body-to-fluid density ratios.

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