Marine Structures 20 (2007) 1–24 A comparative study on 3D wave load and pressure computations for different level of modelling of nonlinearities S.P. Singh a,Ã , Debabrata Sen b a Indian Register of Shipping, 52-A, Adi Shankaracharya Marg, Powai, Mumbai, 400072, India b Department of Ocean Engineering and Naval Architecture, IIT Kharagpur, Kharagpur, 721302, India Received 11 September 2006; received in revised form 27 February 2007; accepted 26 April 2007 Abstract This paper presents a comparative study on the vertical bending moment and pressures between different levels of modelling of nonlinearities based on a 3D time-domain solution scheme. The basic solution method and its successive extensions to model the nonlinear effects are similar to the code LAMP and its various versions [Lin WM, Meinhold M, Salvesen N, Yue DKP. Large amplitude motions and wave loads for ship design. 20th ONR Sym. on Naval Hydrodynamics, Washington D.C.: National Academy Press; 1994. pp. 205–226] although their numerical implementations may differ in details. Results are presented for a large tanker hull and the S175 container hull. It is found that the predictions from the different levels of computations may differ considerably, particularly for the pressures. In general the level 2 computation, which considers modelling of only the nonlinear Froude-Krylov and hydrostatic effects, over-predicts the loads and pressures compared to the most advanced ‘body-exact’ level considered in this paper, where the nonlinearities in the diffraction effect are modelled within certain approximations. r 2007 Elsevier Ltd. All rights reserved. Keywords: Nonlinear wave loads; 3D time-domain simulation; Transient Green’s function 1. Introduction Accurate evaluation of wave-induced pressures and loads are of crucial importance in the structural design of marine vehicles. Research on development of reliable, robust and ARTICLE IN PRESS www.elsevier.com/locate/marstruc 0951-8339/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.marstruc.2007.04.004 Ã Corresponding author. Tel.: +91 22 30519498; fax: +91 22 25703611. E-mail addresses: spsingh@irclass.org (S.P. Singh), deb@naval.iitkgp.ernet.in (D. Sen).