23rd International Towing Tank Proceedings of the 23rd ITTC – Volume II 619 Conference The Specialist Committee on Prediction of Extreme Ship Motions and Capsizing Final Report and Recommendations to the 23rd ITTC 1. INTRODUCTION Dr. J.O. De Kat MARIN, The Netherlands Professor A. Francescutto 1.1. Membership, meetings and University of Trieste, Italy organisation Professor J. Matusiak Membership: The Committee appointed Helsinki University of Technology, by the 22nd ITTC consisted of the following Finland members: Meetings: Seven Committee meetings Professor D. Vassalos (Chairman) were held as follows: Universities of Glasgow and Strath- Shanghai, China, September 1999 clyde, UK Launceston, Australia, February 2000 Osaka, Japan, October 2000 Dr. M. Renilson (Secretary) Glasgow, Scotland, UK, May 2001 Australian Maritime College, Australia, Trieste, Italy, September 2001 and QinetiQ, Haslar, UK Heraklion, Greece, October 2001 Mr. A Damsgaard Glasgow, Scotland, UK, February 2002 Danish Maritime Institute, Denmark (Editorial meeting) Professor H.Q. Gao Organisation: The following working China Ship Scientific Research Centre, groups were established and chairmen ap- Mr. D. Molyneux pointed: Institute for Marine Dynamics, Canada Benchmark Testing for Intact Ship Sta- bility (Umeda) Professor A. Papanikolaou Benchmark Testing for Damaged Ship National Technical University of Ath- Stability (Papanikolaou) ens, Greece Guidelines for Experimental Testing of Professor N. Umeda Intact Ship Stability (de Kat) Osaka University, Japan Guidelines for Experimental Testing of Damage Ship Stability (Damsgaard) In addition, the following corresponding Questionnaire (Molyneux) members contributed greatly to the work of Symbols and Terminology (Frances- the committee: cutto) 23rd International 620 The Specialist Committee on Prediction of Exteme Ship Motions and Capsizing Towing Tank Conference Liaisons: The following Committees and 2. BENCHMARK TESTING FOR organisations have been contacted: Loads and INTACT SHIP STABILITY Responses; Manoeuvring; Waves; IMO (Re- vision of 1966 ICLL, Intact Stability, Harmonisation Group); WEGEMT; CRN; 2.1. Introduction SNAME Technical Panel; EU Thematic Net- work − SAFER EURORO; SRA of Japan − This chapter describes results of the ITTC Panel RR71; COREDES. benchmark testing of intact stability. For these tests, a container ship and a fishing vessel were selected and their hull forms, captive test 1.2. Tasks from the 22nd ITTC data and results of capsizing model experi- ments were provided in advance. On this ba- Coordinate a comparative study of sis, eight research organisations submitted mathematical models for the prediction numerical results. Comparisons between nu- of intact and damage stability in waves. merical and experimental results revealed that The mathematical models will be com- some numerical models are able to predict pared to the results of benchmark tests extreme motions qualitatively, including cap- for two test ships, Ships A and B, as sizing due to parametric resonance and due to specified in Section 7.2 of the report of broaching. Moreover, the importance of sev- the Stability Committee of the 22nd eral factors necessary for capsize prediction is ITTC. noted by mutual comparisons of the numerical studies. Present the guidelines for experimental testing of intact and damage stability, as List of Participating Organisations given in Appendix A of the report of the Stability Committee of the 22nd ITTC, Ship A-1: in the format defined in the ITTC Qual- ity Manual. Flensburger Schiffbau Gesellschaft1 Symbols and terminology should agree (Ms. Heike Cramer) with those used in the 1999 version of Helsinki University of Technology the ITTC S&T List; if necessary, new (Prof. Jerzy Matusiak) symbols should be proposed. Maritime Research Institute Netherlands (Dr. Jan O. de Kat) 1.3. Contents of the 23rd ITTC Report Osaka University (Prof. Naoya Umeda) The following chapters detail the tasks Technical University of Malaysia (Dr. undertaken by the Committee: Adi Maimun) Chapter 2: Benchmark Testing for Intact Universities of Glasgow and Strath- Ship Stability clyde, The Ship Stability Research Cen- Chapter 3: Benchmark Testing for Dam- tre (SSRC) (Prof. Dracos Vassalos) age Ship Stability Chapter 4: Guidelines for Model Testing University of Tokyo (Prof. Masataka Fu- of Intact and Damage Stability jino). Chapter 5: Questionnaire Chapter 6: Symbols and Terminology Chapter 7: Conclusions and Recommen- dations 1 The computer program at FSG was originally Chapter 8: References and Nomenclature developed at Universitat Hamburg. 23rd International Towing Tank Proceedings of the 23rd ITTC – Volume II 621 Conference Ship A-2: (1996). Here the ship model capsized mainly due to parametric resonance in the lower Helsinki University of Technology speed region. The second set was carried out (Prof. Jerzy Matusiak) with a 1/15 scaled model of a 135 gross ton- Memorial University of Newfoundland nes purse seiner (Ship A-2) at the seakeeping (Prof. Don Bass) and manoeuvring basin of the National Re- search Institute of Fisheries Engineering Osaka University (Prof. Naoya Umeda) (NRIFE) by Umeda et al. (1999). In these Universities of Glasgow and Strath- tests, the model capsized mainly due to clyde, The Ship Stability Research Cen- broaching in the higher speed region. The tre (Prof. Dracos Vassalos) principal particulars and body plans of these ships are shown in Table 2.1 and Figures 2.1 This order is not related to the code used and 2.2. In the experiments each ship model in this report. was self-propelled and free from any re- straints, steered on a specified course by using an auto pilot in regular following and quarter- 2.2. Background ing waves. The angular velocities and angles were measured using an optical gyroscope, The trend towards adopting performance- and were recorded on an onboard computer. based criteria in favour of rules-based criteria The reference system used in this report is aiming at safety improvement at sea continues shown in Figure 2.3. unabated at the International Maritime Or- ganisation (IMO), the rule making body of the Table 2.1 Principal particulars of the test United Nations. To facilitate this process, ships. model experiments and numerical simulations tools need to be developed and validated. Items Ship A-1 Ship A-2 However, a standard numerical prediction LPP (length) 150.0 m 34.5 m technique for capsizing has not yet been es- B (breadth) 27.2 m 7.60 m tablished. Therefore, the 22nd ITTC (ITTC, D (depth) 13.5 m 3.07 m 1999) organised a specialist committee for Tf (draught at FP) 8.5 m 2.50 m this purpose and planned benchmark testing T (mean draught) 8.5 m 2.65 m of numerical predictions with selected data T (draught at AP) 8.5 m 2.80 m from free running model experiments. This a chapter summarises the results of these Cb (block coefficient) 0.667 0.597 benchmark tests and highlights the importance kyy/LPP 0.244 0.302 of a number of factors to the numerical pre- (pitch radius of gyration) diction of ship capsizing. xCG 1.01 m 1.31 m (longitudinal position of aft aft centre of gravity from mid- 2.3. Framework of ITTC Benchmark ships) Testing GM (metacentric height) 0.15 m 1.00 m TE (natural roll period) 43.3 s 7.4 s In the intact benchmark testing pro- 2 2 AR (rudder area) 28.11 m 3.49 m gramme, two sets of free running model ex- D (propeller diameter) 5.04 m 2.60 m periments were utilised. The first set was car- P ried out with a 1/60 scaled model of a 15000 TE (time constant of steering 1.24 s 0.63 s gross tonnes container ship (Ship A-1) at the gear) seakeeping and manoeuvring basin of the KR (proportional gain) 1.2 1.0 Ship Research Institute by Hamamoto et al. KR TD (differential gain) 53.0 s 0.0 s 23rd International 622 The Specialist Committee on Prediction of Exteme Ship Motions and Capsizing Towing Tank Conference Among several hundreds of model runs, four runs were selected for each ship for the purpose of ITTC benchmark tests as described in Tables 2.2 and 2.3. Here the nominal Froude number, Fr, and the auto pilot course from the wave direction, χc, are control pa- rameters and the wave height, H, and wave length, λ, are the wave parameters. The initial values of ship motion were specified based on measured data except for the sway velocity, which was assumed to be zero because of Figure 2.2 Body plan of Ship A-2. measurements limitation. For ships A-1 and A-2, the captive model X experiments, e.g. resistance test, self- propul- sion test, propeller open test, circular motion ROLL tests (CMT), roll decay test and so on, were G carried out mainly in NRIFE’s seakeeping and Y manoeuvring basin using an X-Y towing car- PITCH riage. These data together with hull offset data RUDDER and the above mentioned initial values were YAW provided to the participating organisations prior to undertaking any numerical simula- Z tions. Figure 2.3 Reference system. The numerical predictions are firstly re- 2.4. Results quired to qualitatively agree with the corre- The ITTC benchmark test programme for sponding model experiments. Thus, the quali- intact stability commenced in March 2000 tative nature of the results obtained from ex- with numerical results submitted by March periments and numerical calculations are 2001. Numerical prediction methods used by overviewed in Tables 2.4 and 2.5. This in- the participating organisations are outlined in cludes capsize, non-capsize, harmonic roll, Umeda (2001) with numerical results shown sub-harmonic roll, surf-riding and broaching. in Figures 2.4 to 2.6 together with the experi- Here as a judging criterion of broaching the mental results. In agreement with the partici- proposal of Umeda (1999) is used. That is, pating organisations the results have been pre- broaching is a phenomenon in which both the sented anonymously throughout this bench- yaw angle and yaw angular velocity increase mark programme.