CAPSIZING OF VESSELS IN FOLLOWING SEAS

Transcription

1 CAPSIZING OF VESSELS IN FOLLOWING SEAS By: M Reniton For Preentation at AQUAMARINE '95 OCTOBER 1995 REPORT AMECRC C 95/17 AUSTRALIAN MARITIME ENGINEERING CRC LIMITED ACN

2 Capizing of Veel in Following Sea * Martin Renilon Autralian Maritime Engineering CRC Ltd 28 Augut 1995 *Martin Renilon i on part econdment from the Autralian Maritime Autralia. College, Launceton, Tamania, Abtract Capizing in following ea i a highly non linear phenomenon, with the force and moment dependent on the longitudinal poition of the veel in the wave. A four degree of freedom mathematical model which can be ued to decribe the behaviour of veel in following ea ha been developed. Although thi model include heel/yaw and yaw/heel coupling, required to determine the veel' behaviour, it doe not include the full non linear heel retoring moment requiredto tudy veel capizing. The object of reearch into veel capizing i to determine guideline for both deigner and operator to ait them to avoid capizing occurring. Guideline which can be ued by mater to avoid dangerou ituation in following and quartering ea are being developed by 1MO. A propoal which i eay to ue ha been developed by the Japanee delegation, however it doe not include the effect of wave height, or any reference to the tability of the veel. Making ue of a wide range of model experiment, and prediction from a mathematical model developed by Hamamoto et al (1992) it i poible to conclude that veel that meet the 1MO tability criteria are not likely to capize in following ea if they have a metacentric height ignificantly greater than 0.2 time the wave height. It i propoed that the operator of veel with a metacentric height of le than 0.2 time wave height hould take great care in following and quartering ea. They hould adopt the propoed 11MO guideline. Introduction Capizing of mall veel in evere eaway ha been the ubject of reearch for many year. It i one of the few area of hip hydrodynamic that i very unlikely to be able to claim validation from full cale reult - at leat in the foreeeable future! The principal aim of reearch into veel capize i to try and develop guideline to prevent it which can alo be preented in an eay to apply form. A capizing i a very extreme event, involving ubtantial non-linearitie, it i difficult to model the proce mathematically. A a conequence, model are often implified to enable particular phenomena to be invetigated, with the reulting focu on one mode of capize only. Phyical model teting ha alo been carried out, although again often only one mode of capize i invetigated at a time. Recently, a range of free running model experiment have been conducted by a range of author, uch a Kan et al 1990 and 1994, and thee have enabled a range of capize mode to be invetigated, albeit for a limited number of hull hape. Mode of capize in following ea It i well etablihed that there are three principal mode of capize in following ea: pure lo of tability; low cycle reonance; and broaching.

3 Pure lo of tability and low cycle reonance can occur in direct following ea and in thi cae can be invetigated uing a one or two degree of freedom mathematical model. The critical iue in invetigating thee mode of capize i in determining the change in tability in the wave and it i generally accepted thi can be calculated uing fairly traight forward hydrotatic calculation. To invetigate the third of thee capize mode, broaching, a four degree of freedom model in urge, way, yaw and roll i required. Pitch and heave can be neglected if the quai teady aumption i invoked and all the coefficient in the equation of motion are taken to be function of longitudinal poition of the veel in the wave. Mathematical model of behaviour in following ea In order to invetigate the behaviour of veel in following ea, a four degree of freedom mathematical model wa developed a follow (Renilon and Tuite, 1995): Surge m(1_ x ) = Xhl + X prop + X,d + Sway rn(1_y")i = ui1 +Y +Yd +Y Yaw - N")f = Nhf + Nprop + Nd + N Roll L2 (Ix - = + + Kwe + Kprop (4) In equation i - 4 it i aumed that the force and moment on the right hand ide are function of the veel' longitudinal poition in the wave. It i alo aumed that the encounter frequency i low enough uch that the veel i in a quai teady poition in the wave and the force and moment are independent of frequency. The incluion of the roll equation, and the coupling from roll into yaw and way which i preent in the hull term i important a the large heel angle can caue ignificant yawing moment, and hence can influence the lateral behaviour. Typical reult from thi imulation for a 25m Autralian trawler are given in figure 1 and 2 where the reult for three different metacentric height in two wave condition are given. In both figure roll can be een to have a trong influence on the yaw behaviour of the veel. The coupling between yaw-roll and way-roll influence the relative motion (yaw and way) which in turn effect the veel' poition in the wave, dictating it behaviour. A imilar mathematical model ha been developed by Hamamoto et al (1992) and ued to invetigate the capizing of a 115m containerhip in regular following and quartering wave. A ample of the reult i given in figure 3 where the effect of the metacentric height on the wave height to wave length ratio cauing a capize for two wave length and three heading angle i hown. It can be een from thee reult that, in general, a wave length to hip length ratio of 1.5 at an initial heading angle of 30 give the mot critical condition.

4 GU0. Orn CU 2. Ciii o I z z linie (econd) IO Orne (ec onu,) Figure 1. Condition i Figure 2. Condition 2 Wave length = 30m Wave length = 30m Wave teepne (H!2c) = Wave teepne (HJX) = Wave encounter angle = 150 Wave encounter angle = 30 Nominal peed = 12 knot Nominal peed = 12 knot

5 GM(m) L6 L4 12 LO I() L.1.'l.I j U/e 'I_7 o lot apized j Capri zed r(kz) i/li U/rL7 5ot CPizeíj Capized 4ige4G t1 2m GM() L6 L4 L2 LO H/A O ot Capied X apize j U/c I.7.ÀU -A- H4-t.1R H/A Critical rnetaceotric beight leading up to capze VerSl.LS H/A _Ija) 1L/L.5 U/c'. O}at Capized Cacizedj H/A H/A H/A 2m 4 Figure 3 (Taken From Hamamoto et al 1992) Guideline for veel in following ea In order to give guidance to hip operator in following ea, 1MO ha developed a implified procedure for alerting hip operator to the fact that they may be operating in a dangerou condition, and to give them guidance for avoiding thi condition. One of the recent propoal, ubmitted by the Japanee group i decribed by Takaihi (1994). Thi i bet ummaried in figure 4 taken from reference 4. The procedure i to follow the diagram from the top down. A can be een, thi i determined to be valid for wavelength greater than half hip length, and for heading between 0 and ± 45. The mariner etimate the wave length, period and heading angle. V/L i then calculated and the veel' poition on the peedfheading diagram obtained.. Speed and/or heading angle are to be altered if the veel i in the o called 'Surf-riding zone'. Next, V/T i plotted with heading angle. Now, if the veel i in the 'dangerou zone', peed andlor heading have to be altered. Finally, if the encounter period i nearly equal to either the natural roll period for the veel, or to half the natural roll period for the veel, the peed ha to be reduced to avoid thi.

6 Thi procedure i imple to apply and eay to undertand, however it doe not take the wave height, or the veel' tability into account. For example, a veel with a GM of 3m would have to adopt thee guideline when travelling in a following ea with a wave height of only 0.lm. Thi i too trict, and i not what i really intended. What i required i a method for relating the tability of the veel to the wave ize where problem may occur. In order to do thi, a urvey of all known free running model experiment in regular wave wa carried out. Model experiment data from a wide range of different ource covering about 250 capize event on 10 different hull hape in regular wave were obtained. (Reference 1, 2, 5, 6, 7, 8, 9, 10, 11, 13.) The model teted ranged from fihing veel to containerhip covering a range of 'normal' hull form. All the tet were carried out in regular following or quartering ea at a variety of different wavelength, wave teepnee, Froude number and heading. Both wave height and metacentric height were non dimenionalized by dividing by hip length. The reulting plot i given in figure 5. Here, all capize.in following and quartering ea are indicated, regardle of their caue and of the value of wavelength, veel heading and veel peed. In addition, the prediction from Hamamoto et al (1992) given in figure 4 i included in thi figure.

7 Opertjcrt flro for the Mter Jh5p: Stiflction cf i?0 St3biJ.ity Criter13 or uivjent vc : wave 1orth>G.5XShip length, Entinte 1, 1, and i, where Shjp Coure: 4.. 'vo direcioxo i 045 dcree froa ti20 -t- 'I. z,- z,- Encounter Wave Period, Ir J, if hip' peed e. (1) in 5urf-rjdio zor.c Rcduce to peod zone (2),.- (2) in rin1 zone < Reduce to pd zone (3), whc felt large nurzirig. - (3) out cf the norte K Net Step il- o. Li LI 1_I LI 1_4 T : 1/t t t f t t If VIT (i) i jo the dnerour ;ce, redzzc.e t'e pcd t cone cut te zone. if T j.orl, eco! to ta or 11)2, redue the pcd rtber -J, I. Y/TCz ) i oat of the dnrrou none, keep peed and cocrac. Jud1e T Lo corojderntiori te inioun opoed for eajflt.jnin coure 000t2O1 Of Figure 4 (Taken From Reference 4)

8 r rv) N o Capize in Following and Quartering Sea Regular Wave - Augut 1995 /. r /.... / / Waveheight/Ship Length I /. t. model capize prediction (Hamarnoto ) 0.4 Figure 5 Capize in Following and Quartering Sea A can be een, capize do not occur at a metacentric height greater than about 0.2 time the wave height. Of coure, there are alo many condition where the metacentric height i le than 0.2h and a capize doe not reult. Thee occur when the combination of wavelength, veel heading, and veel peed give a ituation which doe not caue a capize, regardle of the fact that the metacentric height i le than 0.2h. The prediction by Hamamoto et ai (1992) of the capize boundary for a 115m containerhip i alo included on thi figure. A can be een, thi alo how that capize do not occur when the metacentric height i above about 0.2h. A capize do not occur when the metacentric height i greater than about 0.2h, it hould not be neceary to apply the propoed new guideline for veel in following and quartering ea when the metacentric height ignificantly exceed thi value.

9 It i therefore uggeted that the propoed procedure for a veel travelling in following and quartering ea hould be a follow: determine whether the veel meet 1MO tability criteria - if not, thi hould be rectified immediately; determine whether the metacentric height i ignificantly greater than O.2h - if not, great cae hould be taken and the propoed new guideline for veel in following ea applied. If the veel meet the 1MO tability criteria and the metacentric height ignificantly exceed O.2h the veel hould be afe and it hould only be neceary to adopt normal good eamanhip procedure. Concluding remark A imple guideline ha been developed by the Japanee delegation at 1MO to ait mariner to avoid a capize in following and quartering ea. Although thi i eay to ue it doe not contain any parameter relating to wave height or veel tability. The reult of a wide range of free running model experiment, together with prediction from a mathematical model for a 115m containerhip, indicate that all capize occur when the GM i le than O.2h. It i therefore propoed that when GM i ignificantly greater than O.2h it i not neceary to apply thi guideline - provided the veel meet the uual 1MO tability criteria. Further work It i recommended that the reult of additional free running model capize, together with thoe from mathematical model, be obtained and plotted on figure 5 to verify that capize do not occur when GM i ignificantly greater than O.2h. Reference Allievi, A G, Caual, S M, and Rohling, G F (1986) "Motion and Stability of a Fihing Veel in Tranvere and Longitudinal Seaway" Society of Naval Architect and Marine Engineer, Spring Meeting Grochawalkj, S (1993) "Comment on the PropOed Safety Criteria for the Operational Guidance of Mater" November Hamarnoto, M., Kim, Y.S., Matuda, A., and Kotani, H., (1992) "An Analyi of Ship Capizing in Quartering Sea" Journal of the Society of Naval Architect of Japan, Vol 171 and 172, "1MO Guidance to the Mater for Avoiding Dangerou Situation in Following and Quartering Sea." SLF 39/3/3. Japanee ubmiion to the Sub-Committee on Stability and Load Line and on Fihing Veel Safety - 39th Seion, December Kan, M, Sanita, T, Taguchi, H, Yaumo, M, and Takaihi, Y, (1990) "Model Tet on Capizing of a Ship in Quartering Wave" 4th International Conference on the Stability of Ship and Ocean Vehicle, 1990, Naple.

10 Kan, M, Saruta, T, Taguchi, H, (1994) "Comparative Model Tet on Capizing of Ship in Quartering Sea" 5th International Conference on the Stability of Ship and Ocean Vehicle, November 1994, Florida Tech. Kawahima, R, Takaihi, Y, Morimura, S, Yohino, T and Saaki, H, (1978) "Model Experiment on Capize and it Prevention for a mall Fihing Boat in Wave" Journal of the Society of Naval Architect of Japan, Vol 143, June Miller, E R, (1975) "A Scale Model Invetigation of the Intact Stability of Towing and Fihing Veel" it International Conference on the Stability of Ship and Ocean Vehicle, March 1975, Univerity of Strathclyde, Glagow. Renilon, M.R. and Tuite, A.J., (1995) "Broaching Simulation of Small Veel in Severe Following Sea" International Sympoium on Ship Safety in a Seaway: Stability, Manoeuvrability, Nonlinear Approach, Kalingrad, May Roden, S, (1962) "Welche Ergebnie Liefern Kenterveruhe mit Modellen" Schifftechnik B. 9, H. 48, Sharp, D H, "A Study of Capizing Motion in Regular Sea at the Towing Tank of the Univerity of California" Northern California Section, Society of Naval Architect and Marine Engineer, March Takaihi, Y., (1994) "Dangerou Wave Condition for Ship Navigating in Following and Quartering Sea" 5th International Conference on the Stability of Ship and Ocean Vehicle, November 1994, Florida Tech. Tuchiya, T, Kawahima, R, Takaihi, Y, Yamakohi, Y "Capizing Experiment of Fihing Veel in Heavy Sea" PRADS '77, Tokyo. Acknowledgment The initial part of the work wa carried out when the author wa on tudy leave at the Univerity of Strathclyde, and wa partly funded by the Autralian Reearch CounciL The author would like to thank the Univerity of Strathclyde and the Autralian Maritime College for making thi poible.