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research-article

Dynamics of slightly curved pipe conveying hot pressurized fluid resting on Linear and Nonlinear Viscoelastic Foundations

[+] Author and Article Information
Olumuyiwa David Owoseni

Department of Mechanical Engineering, University of Lagos, Nigeria
owosenid@yahoo.com

Kehinde/Oluwole Orolu

Department of Systems Engineering, University of Lagos, Nigeria
korolu@unilag.edu.ng

Ayo Oyediran

Department of Mechanical Engineering, University of Lagos, Nigeria
ayooyediran@hotmail.com

1Corresponding author.

ASME doi:10.1115/1.4037703 History: Received April 14, 2017; Revised August 09, 2017

Abstract

One of the most important facilities in the oil and gas industry is the pipeline. These pipelines convey HPHT fluids and transit several kilometres travelling through different seafloor soils. The topography of seabed which act as viscoelastic foundation to the pipeline is rough and irregular thereby making the pipelines to be slightly curved. This erratic behaviour of these soils present several problems to the constructor and threatens the lifespan of the pipeline. The average useful lifespan of pipelines is between 25 - 30 years but improper construction and mal-operation have dropped this span drastically, accounting for more than 50% of pipeline failures, hence this work. The nonlinear governing partial differential equations were derived and solved using energy and eigenfunction expansion methods respectively. The resultant ordinary differential equations were truncated after the fourth mode and solved numerically using eight-seventh order Runge-Kutta code in MATLAB. Two types of foundations were investigated. Both with viscous damping but one is with linear spring, while the other is with nonlinear spring. Bifurcation and orbit diagrams with their corresponding phase portraits showing periodic and chaotic motions of the system trajectories are generated and presented. It was discovered that foundation, curvature and tension stiffen the pipe, while pressure and temperature are of softening effect. Nonlinear stiffness makes the pipe to undergo chaotic oscillation which may result in soil trenching or upheaval which is absent in the linear case, meaning that linear foundations enhance the life span of pipelines than the nonlinear ones.

Copyright (c) 2017 by ASME
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