Session: 06-12-01 Ship Hydromechanics I

Paper Number: 78474

78474 - Estimation of Vertical, Horizontal and Torsional Rigid Body Loads of an Ultra-Large Container Ship (ULCS) in Regular Waves 

Accurate prediction of hull responses and structural loads is an essential aspect during the design of ships, particularly for ultra-large containerships (ULCS). These kinds of containerships are subjected to non-linear wave loads due to the low block coefficient and pronounced bow flare and are also highly susceptible to torsional loads because of the large open cross-section. This work aims to develop a numerical tool based on strip theory for estimating the coupled rigid body motions and wave-induced loads that include torsion acting on ships for both zero and forward speed conditions.

In this numerical code, a  2D -Panel method is used to calculate the added mass and damping coefficients. The forward speed correction is introduced based on STF  theory (Salvensen et al. 1970). A semi-empirical procedure is followed to calculate the surge motion since strip theory cannot estimate it. A body nonlinear approach is followed to capture the major source of nonlinearity in the structural load estimation due to Froude-Krylov and restoring forces. The equation of motion is solved in the time domain. Two kinds of reference frames are followed, i.e., inertial frame and body frame. The coordinate transformation is carried out by means of Euler angles. Case studies are conducted for an Ultra-large container ship in small and large amplitude regular waves for a particular Froude number. Motions and structural loads (vertical, horizontal, and torsional load) RAOs are being investigated for various heading in waves, and the results are compared with the published experimental results. This study’s primary objective is to develop a computationally efficient method to capture linear and non-linear loads, including torsion in small and large amplitude waves.

Keywords: ULCS, Response, hydroelastic,  wave Loads, Strip theory, panel method, STF theory, Nonlinear, Froude-Krylov, Froude number, RAO’s

 

Presenting Author: Vijith P P Indian Institute of Technology Madras

Authors:

Suresh Rajendran Indian Institute of Technology Madras
Vijith P P Indian Institute of Technology Madras