ON THE STATIC INSTABILITY OF FLEXIBLE PIPES CONVEYING FLUID

The problem of fluid flow through flexible pipes has received a good deal of attention in the research literature. Pa.idoussis & Issid (1974) introduced the basic governing differential equations, where it was shown that the system could be subjected to both divergence and flutter instabilities. Laura et al. (1987) investigated bending motion of a simply supported pipeline conveying fluid using a power series method to solve the associated governing equations. Mishra & Upadhyay (1987) used a cylindrical shell model to account for the rotary inertia and shear deformation effects. Concerning system optimization, Borglund (1998) formulated the minimal structural-mass design problem for a fixed critical flow speed. Analysis was performed using the finite element method to solve the associated equation of motion of a cantilevered configuration. Based on the fact that an exact solution for a uniform pipe is available and well established, this study presents a mathematical model for determining the exact critical flow velocity of a pipeline composed of uniform modules. Design parameters include the wall thickness and the length of each module. As a case study, the developed model is applied to a simply supported pipeline consisting of two, three, and more modules. Clear design charts are given showing the functional behavior of the critical flow velocity with the selected design parameters.