Contents lists available at ScienceDirect Applied Ocean Research journal homepage: www.elsevier.com/locate/apor Prediction of nonlinear vertical bending moment using measured pressure distribution on ship hull Kurniawan T. Waskito a , Masashi Kashiwagi a, ⁎ , Hidetsugu Iwashita b, ⁎ , Munehiko Hinatsu a a Department of Naval Architecture & Ocean Engineering, Osaka University, Japan b Department of Transportation & Environmental Systems, Hiroshima University, Japan ARTICLE INFO Keywords: Wave loads Vertical bending moment Nonlinearity Pressure distribution Fiber Bragg grating Rankine panel method CFD ABSTRACT Accurate prediction of wave loads on ships and floating structures is paramount in the structural design stage. Use of a segmented ship model is a common method to quantify the wave loads. Nevertheless, the value could be measured only at segmented sections. To obtain the wave loads at any longitudinal position and to account for nonlinear features in the wave loads more precisely, local quantities of the pressure on the whole ship-hull surface need to be measured along with ship motions in waves. In this paper, an unprecedented experiment using a bulk carrier model has been carried out to measure the spatial distribution of wave-induced unsteady pressure by means of a large number of Fiber Bragg Gratings (FBG) pressure sensors affixed on the whole ship-hull surface, and at the same time the wave-induced ship motions and ship-side wave profile have been measured. In order to see hydrodynamic characteristics in nonlinear and forward-speed effects on measured and analyzed results, some computations with the linear frequency-domain Rankine Panel Method (RPM) and the nonlinear Computational Fluid Dynamics (CFD) method solving the Reynolds-Averaged Navier-Stokes (RANS) equations are made. Favorable agreement is found for the pressure distribution and resulting vertical bending moment between the results of the experiment and corresponding numerical computations. Validation of the measured pressure distribution has also been made through a comparison of the wave-exciting force and moment between the two independent results obtained by integration of the measured pressure over the entire wetted surface of a ship and by direct measurement using a dynamometer. Very good agreement is confirmed in this case, too. As another validation for the wave loads, a comparative study is made with the benchmark test data of a 6750-TEU container ship used for the ITTC-ISSC joint workshop in 2014; which also demonstrates remarkable agreement. The present study may provide a new research technique, especially in the experiment, for predicting the wave- load distribution and for studying local hydrodynamic features in wave-related unsteady phenomena. 1. Introduction Prediction of wave-induced shearing force and bending moment as the wave loads on a ship is of vital importance for evaluating the ship’s structural strength in waves, and hence accurate prediction of wave loads on ships is required. In the analysis of fluid-structure interactions especially for large ships, the so-called two-way coupling in the analysis is prerequisite to account for the influence of flexible deformation of a ship. In fact, much work has been made on ship hydroelasticity pro- blems so far, thereby various methods have been developed for both frequency- and time-domain problems [1–4]. However, the quasi-static response analysis is still deemed as the practical method particularly in the early stage of structural design rather than the direct calculation method involving the dynamic response analysis which is more time- consuming. For that reason, evaluation of the bending moment taking account of primarily rigid-body motions is a dominant part in the study on the wave loads. Comprehensive reviews on the progress in the assessment of wave loads for ships and offshore structures have been presented by the Loads Committee in the ISSC [5,6] and also by the Seakeeping Committee in the ITTC [7]. For instance, Hirdaris et al. [5] summarized related pa- pers published basically in the past three years up to 2011, and Temarel et al. [6] reviewed the progress made in the next three years up to 2014 in the area of wave-induced loads; in which the advantages and dis- advantages of various computation methods including relatively sim- pler potential-flow approaches and time-consuming CFD methods are discussed with reference to accuracy, modeling nonlinear effects, ease of modeling and coupling with structural assessment procedures, and so https://doi.org/10.1016/j.apor.2020.102261 Received 26 March 2020; Received in revised form 21 May 2020; Accepted 15 June 2020 ⁎ Corresponding authors. E-mail addresses: kashi@naoe.eng.osaka-u.ac.jp (M. Kashiwagi), iwashita@naoe.hiroshima-u.ac.jp (H. Iwashita). Applied Ocean Research 101 (2020) 102261 0141-1187/ © 2020 Elsevier Ltd. All rights reserved. T