Experimental Investigation of Invar Edge Effect in Membrane LNG Tanks

[+] Author and Article Information
Mateusz Graczyk

e-mail: Kjetil.Berget@marintek.sintef.no MARINTEK Otto Nielsens v 10, 7052 Trondheim, NorwayMateusz.Graczyk@marintek.sintef.no MARINTEK (USA), Inc., 2603 Augusta #200, Houston, TX 77057 e-mail: Joachim.Allers@4Subsea.comMateusz.Graczyk@marintek.sintef.no

Kjetil Berget, Joachim Allers

e-mail: Kjetil.Berget@marintek.sintef.no MARINTEK Otto Nielsens v 10, 7052 Trondheim, Norway MARINTEK (USA), Inc., 2603 Augusta #200, Houston, TX 77057 e-mail: Joachim.Allers@4Subsea.com

J. Offshore Mech. Arct. Eng 134(3), 031801 (Feb 01, 2012) (7 pages) doi:10.1115/1.4005183 History: Received August 09, 2010; Revised January 20, 2011; Published February 01, 2012; Online February 01, 2012

Sloshing, a violent fluid motion in tanks is of current interest for many branches of the industry, among them gas shipping. Although different methods are commonly combined for analyzing sloshing in liquid natural gas (LNG) carriers, time histories of the pressure in the tanks are most reliably obtained by experiments. Very localized pressures may be important for the structural response of the tank containment system. Moreover, the typical pressure time history duration is similar to the structural natural frequency. Therefore, pressure measurements need to be performed with due account for temporal and spatial distribution. This requires a high sampling resolution both in time and space. Fine spatial resolution becomes especially important when local pressure effects are of interest, such as pressure profile passing a membrane corrugation of Mark III containment or Invar edge of No. 96 containment. In this paper experimental approach applied by MARINTEK for analyzing sloshing phenomenon is presented. The focus is put on investigating effects of Invar edges. A transverse 2D model of a typical LNG carrier is used. Local pressure effects are investigated based on low filling level tests with different wall surfaces: smooth and with horizontal protrusions representing the surface similar to the No. 96 containment system.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Tank used in two-dimensional sloshing experiments: (a) tank cross section, (b) shorter wall with two different setup of pressure panel, and (c) sensor panel with protrusions

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Figure 2

Internal surface of the pressure panel with horizontal protrusions; setup for 25% filling level tests

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Figure 3

Mean of ten maximum pressures full scale measured on the panel with horizontal protrusions: (a) 15% filling level and (b) 25% filling level

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Figure 4

Example of a large impact on the smooth wall for h = 15%H, ω/ω1  = 0.965; full scale pressures for n sensors in each row (row numbers increasing with height); n is a number of active sensors, commonly three, but for example in rows 1, 5, 11, 13, 14, and 21 one or two sensors are inactive

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Figure 5

Mean of ten maximum pressures full scale on the smooth panel (—×—) and panel with horizontal protrusions (—o—), row numbers increase with height; dotted vertical lines show the location of protrusions: (a) h = 15%H, ω/ω1  = 0.97 and (b) h = 25%H, ω/ω1  = 0.98

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Figure 6

Fluid impact on the wall with horizontal protrusions for h = 15%H, ω/ω1  = 0.97: (a)–(d) frames stepped with dt = 23.7 ms full scale

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Figure 7

Fluid impact on the wall with horizontal protrusions for h = 25%H, ω/ω1  = 0.98: (a)–(d) frames stepped with dt = 47.3 ms full scale

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Figure 8

A typical pattern of the pressure time history on the wall with horizontal protrusions: (a) registered by a sensor in row 9 [compare Fig. 5a] for h = 15%H, ω/ω1  = 0.97 and (b) registered by a sensor in row 15 [compare Fig. 5b] for h = 25%H, ω/ω1  = 0.98



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