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PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping and M. Papadrakakis
Nonlinear Stability of Shells Conveying Fluid Flow
M. Amabili1, K. Karagiozis2 and M.P. Païdoussis3
1Department of Industrial Engineering, University of Parma, Italy
M. Amabili, K. Karagiozis, M.P. Païdoussis, "Nonlinear Stability of Shells Conveying Fluid Flow", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 133, 2008. doi:10.4203/ccp.88.133
Keywords: nonlinear, cylindrical shells, experiments, comparison to theory, stability, flow, subcritical bifurcation, fluid viscosity.
Thin circular cylindrical shells supported at both ends and subjected to internal or external axial fluid flow may be found in many engineering and biomechanical systems. There are many applications of great interest in which shells are subjected to incompressible subsonic flows. For example, thin cylindrical shells are used as thermal shields in nuclear reactors and heat shields in aircraft engines; they may also be found in jet pumps and heat exchangers; they are used as storage tanks and thin-walled piping for aerospace vehicles. Furthermore, in biomechanics, veins, pulmonary passages and urinary systems may be modelled as shells conveying fluid.
In particular this paper presents experimental results for clamped aluminium shells and a recent nonlinear theoretical formulation that accounts for the effect of fluid viscosity. The shell system loses stability by divergence (which is a static pitchfork bifurcation of the equilibrium, exactly the same as buckling) when the flow speed reaches a critical value. According to the few available studies the divergence is strongly subcritical, becoming supercritical at larger amplitudes . It is very interesting to observe that the shell system has two or more stable solutions concurrently, related to divergence in the first mode or a combination of the first and second longitudinal modes, much before the onset of the pitchfork bifurcation. This means that the shell, if perturbed from the initial configuration, may be subjected to severe deformations causing failure at flows much smaller than the critical velocity predicted by linear theory.
The novel features of the present study are:
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