Three Dimensional Nonlinear Dynamics Of Cantilevered Cylinders In Axial Flow

Author : Ahmed Abdelbaki
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (119 download)

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Download or read book Nonlinear Dynamics of Hanging Tubular Cantilevers Subjected to Internal and External Axial Flows written by Ahmed Abdelbaki and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "A pipe conveying fluid is a typical example of a fluid-structure-interaction problem, in which the pipe becomes unstable at sufficiently high flow velocities via static divergence or oscillatory motion, namely flutter, depending on the boundary conditions. That particular system has been under study for almost a century and it has become a paradigm in dynamics, especially the cantilevered pipe, not only because of the rich dynamics that this system exhibits, but also for its industrial importance. In addition, the stability of a cantilevered cylindrical structure subjected to axial flow has been investigated over decades; a relatively recent challenge is to consider the inverted problem, in which the upstream end of the cylinder is free and the downstream one is clamped. This inverted system was found to lose stability via flutter at low flow velocities, with potential applications in energy harvesting.Examining the dynamics of a cantilevered pipe simultaneously subjected to internal and inverted external axial flows is the main objective of this thesis. This system has several industrial applications, such as heat exchangers, drill-strings, and brine-strings that are used in solution mining; moreover, in this latter application, the salt-mined caverns are subsequently used for hydrocarbon storage and retrieval.Linear and nonlinear theoretical models are developed in this thesis to investigate the stability and to examine the nonlinear dynamics of three systems. Specifically, the systems under study are: (i) a cantilevered cylinder subjected to inverted external axial flow, (ii) a cantilevered pipe discharging fluid with inverted external flow confined over the whole length of the pipe, and (iii) a cantilevered pipe simultaneously subjected to internal flow and inverted external axial flow confined only over its upper portion. The equations of motion are derived using the extended Hamilton's principle and via a Newtonian approach, in some cases with separate derivation of the fluid-related forces. Each equation is discretized using the Galerkin method to a set of ordinary differential equations which are then solved using the pseudo-arclength continuation method and a direct time integration technique for nonlinear analysis. The results obtained with all three models are compared to experimental observations reported in the literature and to theoretical predictions of earlier linear models. Furthermore, the influence of various system parameters on the dynamical behaviour of these systems is investigated theoretically.New sets of experiments have been conducted for the third system, and the results are presented in this thesis, supported by a linear theoretical analysis. These experiments are aimed at investigating the effect of the external annular flow on the stability of the system by increasing the ratio of annular to internal flow velocities. It was found that increasing this ratio destabilizes the system drastically. Furthermore, improvements to the initial form of the theory are implemented, which enable achieving good to excellent agreement between theory and experiments, both qualitatively and quantitatively"--