Date of Award

Summer 1978

Document Type

Dissertation

Degree Name

Doctor of Engineering Science in Mechanical Engineering

Department

Mechanical Engineering

First Advisor

Amir N. Nahavandi

Second Advisor

Roman I. Andrushkiw

Third Advisor

James L. Martin

Fourth Advisor

Benedict C. Sun

Abstract

A finite element model for the study of solid-fluid interaction, with applications in flow-induced vibration analysis of reactor vessel and heat exchanger internals, is presented. The model is based on the discretization of the solid equation of motion and the fluid continuity and momentum equations and employs the solid displacements together with the fluid pressure and velocity components as the nodal degrees of freedom. This permits a realistic and accurate implementation of boundary conditions, in contrast with methods using solid displacements and fluid pressure as the only field variables. The numerical solution of the resulting matrix equation, involving non-symetric matrices, is achieved by a combination of matrix decomposition, iterative scheme and analytic integration which allows the application of the elemental matrices, rather than the system global matrices, at considerable economy in computer storage and running time. Plane triangular finite elements for fluid, solid and solid-fluid continua and equivalent mass, damping and stiffness matrices and interaction load array have been developed for the study of wave propagation phenomena in a two-dimensional flow field. This is verified by solving a wave propagation flow problem consisting of water, between two elastic parallel plates, initially at rest and accelerated suddenly by applying a step pressure at one end. The results obtained are in good agreement with a previous study based on the finite element discretization of the two-dimensional wave equation. Futhermore, the results are also compared with those obtained for flow between two rigid parallel plates. These results indicate the development of water hammer phenomenon and pressure surge in the transverse direction, for the elastic wall case, which may have important implications in the design of fluid systems.

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