0
Ocean Engineering

Stern Slamming of a LNG Carrier

[+] Author and Article Information
Jan Oberhagemann

 Germanischer Lloyd AG, Vorsetzen 35, Hamburg 20459, Germanyjan.oberhagemann@gl-group.com

Michael Holtmann

 Germanischer Lloyd AG, Vorsetzen 35, Hamburg 20459, Germanymichael.holtmann@gl-group.com

Ould el Moctar

 Germanischer Lloyd AG, Vorsetzen 35, Hamburg 20459, Germanyould.el-moctar@gl-group.com

Thomas E. Schellin

 Germanischer Lloyd AG, Vorsetzen 35, Hamburg 20459, Germanythomas.schellin@gl-group.com

Daewoong Kim

 Daewoo Shipbuilding & Marine Engineering Co. Ltd., 541 Daewoo Center Building Namdaemunro 5-Ga, Jung-Gu 656-714, South Koreadaewoong@dsme.co.kr

J. Offshore Mech. Arct. Eng 131(3), 031103 (Jun 02, 2009) (10 pages) doi:10.1115/1.3124131 History: Received July 03, 2008; Revised October 05, 2008; Published June 02, 2009

Rational assessment of stern slamming of a large twin screw liquefied natural gas (LNG) carrier comprised prediction of hydrodynamic impact loads and their effects on the dynamic global structural behavior of the hull girder. Linear theory obtained regular equivalent waves that caused maximum relative normal velocities at critical locations underneath the ship’s stern. Reynolds-averaged Navier–Stokes computations based on the volume of fluid method yielded transient (nonlinear) hydrodynamic impact (slamming) loads that were coupled to a nonlinear motion analysis of the ship in waves. At every time step of the transient computation, the finite volume grid was translated and rotated, simulating the actual position of the ship. Hydrodynamic loads acting on the hull were converted to nodal forces for a finite element model of the ship structure. Slamming-induced pressure peaks, typically lasting for about 0.5 s, were characterized by a steep increase and decrease before and after the peak values. Shape and duration agreed favorably with full-scale measurements and model tests carried out on other ships, indicating the plausibility of our numerical predictions. Hull girder whipping was analyzed to investigate dynamic amplification of structural stresses. Short-duration impact-related slamming loads excited the ship structure to vibrations in a wide range of frequencies. Excitation of the lowest fundamental eigenmode contributed most to additional stresses caused by hull girder whipping. Although, for the cases investigated, longitudinal stresses and shear stresses caused by quasisteady wave bending were uncritical, we obtained a significant amplification (up to 25%) due to the dynamic structural response.

Copyright © 2009 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Stern region of the LNG carrier, seen from below

Grahic Jump Location
Figure 2

Locations of investigated slamming loads

Grahic Jump Location
Figure 3

Maximum normal relative velocities obtained from long-term statistics and restricted by wave amplitude

Grahic Jump Location
Figure 4

Volume grid for wave 2

Grahic Jump Location
Figure 5

Time histories of heave and pitch motions (upper graph) and accelerations (lower graph)

Grahic Jump Location
Figure 6

Time history of normal relative velocity

Grahic Jump Location
Figure 7

Time histories of computed slamming pressure in [kPa] for wave 1 (highest values), wave 2 (somewhat lower values), and wave 3 (lowest values)

Grahic Jump Location
Figure 8

Impact peaks of hydrodynamic force

Grahic Jump Location
Figure 9

Time histories of computed and measured pressures in the stern region of a large containership

Grahic Jump Location
Figure 10

Computed pressure distribution for wave 2 occurring at time of peak slamming pressure

Grahic Jump Location
Figure 11

Time histories of vertical acceleration (highly oscillating curve) in [m/s2] and vertical force (other cuve) in [kN] at stern (upper graph) and at bow (lower graph) for wave 1

Grahic Jump Location
Figure 12

Frequency spectra of vertical acceleration at stern (left) and at bow (right) for wave 1

Grahic Jump Location
Figure 13

Hull girder modes at eigenfrequencies of 0.79 Hz (upper graph) and 3.59 Hz (lower graph) for wave 1

Grahic Jump Location
Figure 14

Time histories of elastic (highly oscillating curve), rigid body (thicker curve), and superimposed (total) vertical acceleration (curve oscillating about the thicker curve) in [m/s2] at stern (left) and at bow (right) for wave 1

Grahic Jump Location
Figure 15

Time histories of longitudinal midship quasi-static wave bending stress (unidentified curve), slamming stress (curve identified by 22593 kN/m2), and superimposed (total) stress (curve identified by −105939kN/m2) in [kN/m2] for wave 1

Grahic Jump Location
Figure 16

Longitudinal stress distribution in kn/m2 at time of maximum midship dynamic stress amplification (upper graph) for wave 1

Grahic Jump Location
Figure 17

Elastic (highly oscillating curve), rigid body (thicker curve), and superposed (total) vertical acceleration (curve oscillating about the thicker curve) in [m/s2] at stern (left) and at bow (right) for wave 2

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In