Friday, December 10, 2004
1:00pm – 2:00pm
Professor Michael P.
Paidoussis
Department of
Mechanical Engineering
McGill University
ÒSome
Unresolved Issues in Fluid-Structure InteractionsÓ
Abstract:
Three of the many
unresolved or partly resolved issues in fluid-structure interactions are discussed in this
paper: (i) the existence of post-divergence flutter of shells with supported
ends (an inherently conservative system in the absence of dissipation)
subjected to axial flow; (ii) the possible instability of shells with mismatched
end-supports containing flow, at infinitesimal flow velocities; (iii) the stability
of aspirating cantilevered pipes.Ó
The question of existence
of post-divergence flutter of shells containing or immersed in axial flow
appears to be resolved at last; although predicted by linear theory, it does
not arise in nonlinear theory and it has not been observed in experiments. The
question is discussed here in a wider context, also including pipes conveying
fluid, pulmonary passages with flow, and cylinders in axial flow, and some new
insights are gained.
The definitive answer as
to whether fluid-conveying shells with the upstream end clamped and the
downstream one simply supported actually lose stability at infinitesimal flow
velocities has proved to be elusive.
The saga is retold of the see-saw progress towards unravelling this
conundrum, and some further thoughts are presented.
Finally, the question of
stability of aspirating cantilevers was thought to have been totally resolved,
till it was discovered that the theoretical proof was, at best, incomplete.
This question, which is related to Feynman's quandary on aspirating rotary
sprinklers, is re-examined and it is shown that it is only deceptively simple.