FLOW-INDUCED VIBRATION OF CURVED PIPE STRUCTURES

YI-CHEN LIU, Purdue University

Abstract

Mathematical models and a general numerical approach based on the structural impedance are developed for the dynamic study of curved flow-conveying pipe structures. The primary advantage of the numerical approach is that the dynamic interactions between the flowing fluid and the pipe structures, as well as the coupling effects between the in-plane and the out-of-place pipe motions can be fully accounted for. The algorithm also has the capability of considering the dynamic stability phenomenon. A procedure including the stability criterion is suggested. For the verification of the algorithm and the computer code, several dynamic stability problems which have been previously studied experimentally and analytically were considered. This includes straight pipes and simple curved pipe models. Special attention is focused on the assessment of the effect of torsional inertia. After validating the computer code, more complicated structural models and flowing conditions were considered. This includes pipes with intermediate rigid or elastic supports, pipes connected with an elbow, the transient fluid flows, and the pipe-whipping problems due to sudden change of boundary constraints. In addition, parametric studies are conducted for the model shapes of pipe vibration and the stability conditions. Parameters considered are the change of support location, pipe geometry and the flow velocity. A more general helical pipe model was presented. The difficulty of the analysis is that the motions of a helical pipe contain strong interactions between the in-plane motion and the out-of-plane motion. For a simple plane curved pipe, these two components are independent and thus can be treated separately. For each component of the motion, formulations were derived and computer codes were developed. Dynamic responses, stability conditions and parametric analyses were obtained for the similar cases discussed previously for the plane curved pipes. Finally, a helical circular pipeline with constant pitch angle was analyzed by combining the formulation for each component of motions. The special feature of a helical pipeline is that strong couplings exist among the components. A general purpose computer code was developed for the numerical solutions.

Degree

Ph.D.

Subject Area

Civil engineering

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