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Research Papers

A Physical and Numerical Modeling for Launching of Jackets (Case Study on Balal PLQ Platform)

[+] Author and Article Information
M. R. Honarvar, Moharam D. Pirooz, Mohammad R. Bahaari

Civil Engineering Department, University of Tehran, Tehran, Iran

J. Offshore Mech. Arct. Eng 130(3), 031004 (Jul 15, 2008) (8 pages) doi:10.1115/1.2904714 History: Received April 03, 2007; Revised November 11, 2007; Published July 15, 2008

Abstract

Platform structures are commonly utilized for various purposes including offshore drilling, processing, and support of offshore operations. A jacket is a supporting structure for deck facilities, stabilized by piles driven through it to the seabed. In a jacket design, operational and environmental loads are very important and must be intensively investigated to secure the stability of structures during their service life, as well as installation phase. The main purpose of this research is to evaluate the results of physical modeling for the launch operation of jackets from barge into the sea, as the most hazardous stage in the installation of a platform, and compare them to those of numerical modeling. Both physical and numerical modeling parameters are described and they are examined on a prototype platform, i.e., Balal oil field production and living quarter platform that is a 1700 tone, eight-legged jacket located in the center of Persian Gulf, some $100km$ distance from Iranian Lavan Island. It is found that both numerical and physical methods can describe the motion of the barge similarly well, but some differences are traced in the motion of jacket. The inequalities are, then, appeared to be due to the Froude-type parameters applied for modeling purpose. One notable fact investigated in this research is the necessity for choosing Reynolds–Froude type in the physical modeling of the launch, instead of Froude type. This is because, in addition to the importance of gravitational and inertial forces, the viscosity affects the drag hydrodynamic force, as well. It should be noted that viscosity and consequently drag coefficient in Froude type modeling cannot be quite applicable and this causes the difference observed between the results of physical and numerical modeling. Although there have been so many jacket launching designed and probably their physical models have been tested, but to the best of our knowledge from the literature, there was found no study on Reynolds–Froude physical modeling of jacket launch phenomenon. If one is interested in practicing a Reynolds-Froude physical modeling, it could be done either in a centrifuge test or by using a fluid with lower viscosity dependent on the scale of model, or even by finding a fluid (with new viscosity and new density) and a new gravity to have simultaneously the Froude and the Reynolds similarity laws satisfied.

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Figures

Figure 1

Balal platforms view after installation

Figure 2

Balal PLQ jacket view

Figure 3

Numerically calculated time trajectory

Figure 4

Numerically calculated time trajectory at specified times

Figure 5

Physical model (scale=1:200)

Figure 6

Physically calculated time trajectory

Figure 7

Horizontal displacement diagram

Figure 8

Vertical displacement diagram

Figure 9

Numerically calculated horizontal velocity diagram

Figure 10

Numerically calculated vertical velocity diagram

Figure 11

Numerically calculated rotational velocity diagram

Figure 12

Jacket horizontal displacement diagram

Figure 13

Jacket vertical displacement diagram

Figure 14

Variation of drag coefficient with Reynolds number (generated based on Ref. 8, Figs. 7–85)

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