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CONTENTS
Volume 1, Number 3, September 2011
 

Abstract
A method for calibrating a laser profiling system for seafloor micro-topography measurements is described. The system consists of a digital camera and an arrangement of six red lasers that are mounted as a unit on a remotely operated vehicle (ROV). The lasers project as parallel planes onto the seafloor, creating profiles of the local topography that are interpreted from the digital camera image. The goal of the calibration was to determine the plane equations for the six lasers relative to the camera. This was accomplished in two stages. First, distortions in the digital image were corrected using an interpolation method based on a virtual pinhole camera model. Then, the laser planes were determined according to their intersections with a calibration target. The position and orientation of the target were obtained by a registration process. The selection of the target shape and size was found to be critical to a successful calibration at sea, due to the limitations in the manoeuvrability of the ROV.

Key Words
calibration; laser profiling; image correction; registration; sediment roughness; microtopography.

Address
Kathryn R. Loeffler and Nicholas P. Chotiros :Applied Research Laboratories, The University of Texas at Austin, P.O. Box 8029, Austin,
TX 78713-8029, USA

Abstract
A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.

Key Words
incompressible SPH; rigid body; free surface flow; pressure Poisson equation.

Address
Abdelraheem M. Aly, Mitsuteru Asai and Yoshimi Sonoda : Civil Engineering Department, Faculty of Engineering, Kyushu University, Japan

Abstract
In combat operations, naval ships may be subjected to considerable air blast and underwater shock loads capable of causing severe structural damage. As the experimental study imposes great monetary and time cost, the numerical solution may provide a valuable alternative. This study emphasises on numerical analysis for optimization of stiffened and unstiffened plate

Key Words
stiffened/unstiffened plate; blast loading; ship hull; dynamic response; Explicit/Implicit schemes.

Address
Muhsin Hamdoon and Nader Zamani : Dept. of Mechanical, Automotive, and Materials Engineering, University of Windsor, Windsor, Canada
Sreekanta Das : Dept. of Civil and Environmental Engineering, University of Windsor, Windsor, Canada

Abstract
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Key Words
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Address
Y.H. Bae :Texas A&M University, College Station, TX, USA
M.H. Kim :Civil Engineering, Texas A&M University, College Station, TX, USA

Abstract
The stochastic nonlinear dynamic behavior and probability density function of ship rolling are studied using the nonlinear dynamical systems approach and probability theory. The probability density function of the rolling response is evaluated through solving the Fokker Planck Equation using the path integral method based on a Gauss-Legendre interpolation scheme. The time-dependent probability of ship rolling restricted to within the safe domain is provided and capsizing is investigated from the probability point of view. The random differential equation of ships

Key Words
nonlinear ship rolling; noise excitation; path integration method; Fokker Planck Equation.

Address
Arada Jamnongpipatkul, Zhiyong Su and Jeffrey M Falzarano : Department of Civil Engineering, Texas A&M University, College Station, Texas, USA


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