Arabian Journal for Science and Engineering

, Volume 37, Issue 7, pp 2017–2033 | Cite as

On the Design of a Suspension System for Oil and Gas Transporting Pipelines Below Ocean Surface

Research Article - Mechanical Engineering
First Online:
Received:
Accepted:
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Abstract

Expanding demand on oil transportation through submarine pipeline brings an immediate need for a proper design of underwater transporting pipeline system. A substantial amount of work has been conducted in the modeling of submarine pipelines laid on the seabed with the awareness of the downsides of such design approach. The high cost and labor intensiveness, due to installation and maintenance, are some of the disadvantages of such design. This paper discusses a new design of suspended pipelines which can be considered a favorable option as opposed to laying oil pipelines on the sea floor. An optimum design of a suspended oil transporting pipeline is considered in this study and a simple nonlinear mathematical model is developed to predict the dynamic behavior of the pipeline. The system consists of buoys as a suspension mechanism, transporting pipeline and vibration absorbers against ocean waves and vortex-shedding excitations. Nonlinearities in the model are due to vortex-shedding effects and fluid damping of the pipeline. The system design parameters considered for optimization are the absorber natural frequency, damping ratio and the buoy diameter. Other system parameters are assumed to be given to avoid design complexity. The design criterion is to minimize vibration amplitude of the pipeline and consequently the internal normal stresses with given constraints of maximum absorber displacement and buoy maximum diameter.

Keywords

Underwater suspended pipeline Flow-induced vibrations Optimum design Vortex shedding 

List of Symbols

Rd

Reduced damping factor

Lp

Pipeline segment length

Fw

Ocean wave exciting force

ωw

Ocean wave excitation frequency

Hw

Ocean wave amplitude

Fs

Vortex shedding transverse force

Dp

Pipeline external diameter

Db

Buoy diameter

t

Time in seconds

tp

Pipeline wall thickness

tb

Buoy wall thickness

U

Ocean current speed

Cl (t)

Time varying lift coefficient

ρw

Ocean fluid density

ρb

Buoy material density

ωs

Vortex-shedding frequency

St

Strouhal number selected to be 0.2

xb

Buoy response

xp

Pipeline response

xa1

Buoy absorber response

xa2

Pipeline absorber response

Mb

Buoy mass including added mass

Mp

Equivalent pipeline mass including added mass

ma1

Buoy absorber mass

ma2

Pipeline absorber mass including added mass

m

Pipeline mass per unit length

Kb

Hydrostatic restoring coefficient of buoy

Kp

Pipeline equivalent stiffness

Ka1

Buoy absorber spring constant

Ka2

Pipeline absorber spring constant

Cb

Wave damping coefficient for the buoy–water interaction

Cp

Pipeline structural damping coefficient

Ca1

Buoy absorber damping coefficient

β

Pipeline fluid damping coefficient

α

Pipeline absorber fluid damping cefficient

h

Height of the buoy above water surface

h1

Immersed depth of buoy in water

da2

Pipeline absorber diameter

ωnp

Pipeline fundamental mode frequency

W1, W2, W3

Objective function weighing factors

Y

System objective function

\({\zeta _{\rm p}}\)

Pipeline structural damping factor

fd

Pipeline absorber damping factor (dimensionless)

Ur

Reduced velocity

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Copyright information

© King Fahd University of Petroleum and Minerals 2012

Authors and Affiliations

  1. 1.National Robotics and Intelligent Systems CenterKing Abdulaziz City for Science and TechnologyRiyadhSaudi Arabia
  2. 2.Mechanical Engineering DepartmentKing Saud UniversityRiyadhSaudi Arabia
  3. 3.King Abdulaziz City for Science and Technology KACSTRiyadhSaudi Arabia

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