' 𝑘
Jurnal
Kapal: Jurnal Ilmu Pengetahuan dan Teknologi Kelautan
(Kapal:
Journal
of Marine Science andTechnology)P
journalhomepage:http://ejournal.undip.ac.id/index.php/kapal
2301-9069 (e) 1829-8370 (p)
Experimental Investigation of Bow Slamming on a Ship: The Effect of Weight and
Impact Angle H)
Checkfor
Suandar Basoir), Andi NadiaHimaya2),Faizal Arya Samman3),AndiDianEkaAnggriani11,
Rosmani11
11Department of NavalArchitecture,Facultyof Engineering, Hasanuddin University, Gowa92171,Indonesia
2)Department of Transportation and Environmental System, Hiroshima University, Hiroshima 739-8527, Japan
3)Department ofElectrical Engineering, Faculty of Engineering, Hasanuddin University, Gowa92171,Indonesia
*'
CorrespondingAuthor:[email protected]Article Info Abstract
Keywords:
Bow Slamming;
Dropping Test;
ImpactPressure:
PeakPressure Coefficient
The impact pressure induced by slammingcan imply physical damage ona ship. The high probability of the slamming impact ison the bowpartin the actual sea state. In thispresentstudy,the slamming induced pressure on the bow flareof a shiphave beeninvestigated through the experiment. The experimentwasschemed by the dropping test basedonfree-falling bodyinthewavetank, wherein the bowof the ship modelwasinclinedinseveral impact angles0°to30°tothefree-watersurface.To measure slamming impact pressure actingon the bowflare,the piezoelectricsensorsSI, S2, S3,S4 were attached to the bow section and installedon acomputer.Asthe obtained results, the impact pressureonbow flare occurredinashort time duration caused by slamming. The discrepancyof the peak impactpressure between ship model weight of 2.42kg and7.29kgfor theimpact angle0°is 70.36%SI,69.52%S2,68.97%S3,and 68.34% S4. For the relative impact angle of 30°, the discrepancy is 67.02%SI,65.73%S2,58.51%S3,and 48.21% S4.Thetendencyof thepeak pressure coefficient at the sequenced impact points SI, S2, S3, S4 is similarfor all impact angles 0°, 10°, 20°, and30°.The peak pressure coefficient due to the full load condition is highestinthe nearest bottom part, and the peak pressurecoefficients due tothe lightship condition highest in thenearestbottompartcausedby the Article history:
Received:11/01/21
Lastrevised:06/01/21
Accepted:07/02/21 Available online:07/02/21 Published:28/02/21
DOI:
https://doi.org/10.14710/kapal. small impact angle.
vl8il.35663
Copyright©2021 Kapal:JurnalIlmu Pengetahuan dan Teknologi Kelautan. This is an open access article under the CC BY-SA license (https://creativecommons.Org/Iicenses/by-sa/4.0/).
1. Introduction
Whenaship sailing in waves is sometimes experiencing slammingevents.Slamming isa phenomenonthat indicates nonlinearinteractionbetweenshiphulland wavewithinthewater entry process and resultsshort durationof highforce and pressure and dynamic response. Theeffect of this phenomenoncan imply damage, capsizing, or sinking. Therefore, the characteristicsofshipslamming should beinvestigated,andthen theinvestigationresults are theconsiderationsin obtaining proper ship hullform and construction designs.
Subjected to thestudyof slammingimpact, vonKarman [1] and Wagner[2]had firstly conducted,hereinafter the enormousnumberofstudiessubjected tothe slamming impactsand itseffects on a ship has beencarried out by using numerical and experimental methods.The following,some related studies in the last decade have been presented.The investigationsof slamming induced pressure and load in two-dimensional (2D) ship model section have been developed by usingthe finite elementsoftwareABAQJJS[3], explicit FEMcode LS-DYNA[4], finite element code ABAQUS[5],combined strip theory, and smoothed particle hydrodynamics (SPH) approach[6],the boundaryelement method (BEM) code and FLUENT code[7],2D generalized Wagner model[8],the moving particle semi-implicit (MPS)method involving Prandtl s mixinglength method and the -epsilon method [9], Although the2Dapproach has sufficient results, however,it isstillnot relevant in the reality of the slamming problem. Also, this becomes less appropriateiftheresultsare validated using the experimental results.
The slamming investigations using thethree-dimensional section have also been carried out by usingsome methods suchasthe Wagner approach and the boundary elementmethod(BEM)[10], the coupled model of3DRankine panelmodel, 3D FEM,and 2DGWM[8], the3Dtime-domain nonlinear hydroelastic method [H], seakeeping codeandsimplified method [121.momentumimpactmethod and dam-breaking method[13].Those studieshaveshownhigh accurate results by the developed numerical method, and then these results have been validated with the experimentalresults.
' Thewater entryof a floating bodyis interestedin beingstudied regardingthe slamming loadsactingona floating body.
The droppingtest of ashipmodel witha free-fallapproachisthemost appropriate way todescribe thewater entryof a floating body and slammingevent.However,this method needsaspecialized technique and proper measurement device to obtainaccurateresults. Therefore, the consideration of the experimentequipmentandexperimentaldesignisanappropriate way. Nevertheless,anexperimental investigation remains to be needed to interpret and enrich physical understandingfrom theresultant nonlinearinteractionbetween shipand wave-inducedslammingimpact.
In this present study, the impact pressure resulted through dropping test by free fall way ofa ship model has been investigatedto characterize theeffect of the relative impact angle and the model weighton bow slamming. The ship s bow anglestothewater-free surface have been considered from 0°to 30°, andfour sensordeviceshave been attachedtothebow flaresurface of the ship model.By characterizingbow slamming through the experimental investigation, the bow slamming of ashipin waves could beinterpreted.
2. Methods
The ship slammingisdescribedbyan impact resulting fromcontact betweenaship'sbodyandfree surface after lifting upwardonawave.By this description, the dropping testofashipmodel has been conducted to obtainanimpact pressure caused byslamming.Also,the influenceofthe weight andbowimpactangleof the ship wereinvestigatedin thisexperiment.
The weightsof the ship modelwere considered 2.42 kg and 7.29 kg, and they were respectively defined as the lightship and full loading conditions.
The experiment was performed at wave tank, Ship Hydrodynamics Laboratory, Naval Architecture Department, Hasanuddin University,Indonesia. Thesizeof thewavetank lengthis 20m, the width is 1.5m,and the depthis1.3m. The ship type thatwas used in the experiment isacontainer. The lines plan of the ship is shown in Figure1.The shipmodel scale is 1:75, and itwasmadeof fiberglass, as shown inFigure1.Thescaleof the ship modelconsideredthesizeof the wave tank.
The main dimensions of the actual ship and modelare provided in Table 1. In the bow part, the pressure sensors were attachedto capturethe slamming induced pressure.The experimental details arediscussed accordinglyof theship model, experimentscheme,experiment equipment,and device.
Table 1. theMainParticularsoftheActualShipandModel Actual (m) Model (m) Dimension
Lengthoverall, LoA Length waterline,LwL
Lengthbetween perpendiculars, LbP Breadth,B
Depth,H
Draft,T_
74.49 72.40 67.70 11.50
0.993 0.965 0.929 0.153 0.096 0.080 7.20
6.00
jmrz
'ÿ
i: K
’
i i i * i
ji
“-
___ MmmmmmmmBk
*1-— T— *| " '7
,
-v
ci w! Mi Cli .)-*f-« - 4§
\
/
Figure 1. the Ship Lines Plan and Ship Model
K
Jurnal
m
7S~
1,5m 1,5m
Figure 2. the Experimental Scheme of The Dropping Test
V:!
GND TTLAO VCC
(a) (b)
Wk % PC
mm £5
(c) (d)
Figure3. the Installation of thePressure Sensor Device;(a) Piezoelectric KnockSensor,(b)Arduino Mega,(c)Breadboard, (d) Block Diagram
's"
«
/“
•
\<EFigure 4. the Illustration of Piezoelectric Knock Sensors Attached Vertically in Bow Flare of The Model
The experimental method is the dropping test withfree fall way. For droppinga ship model, the droppingtoweras experiment equipmentwasconstructedabove the wavetank construction. The ship model was hungusingaropeinthe droppingtower.The distance between the shipmodel in the dropping tower and the water-free surface in the wave tank wasconsidered1.5 m forreachinga relativeimpactangle onthebowpartafterdroppinga ship model. Thebowangleofthe ship model was fixedfrom0°to30°tothewater-free surface.
In thedropping tower,thebowangleof the ship modelis adjusted andkept byusingtwo ropesthat aretiedonthe rear and middlepartofthe shipmodelconnectedtothe dropping tower. Then, the bow angleis maintaineduntil reachingthe water-free surface.Also, two ropesare needed for tying the starboard and portsideof the ship modelconnected to the droppingtower to avoidaheeling conditionof the ship model, and theyare freely released during the dropping process. The ship model with theproper condition regarding theexpected bow angelis dropped tothewater-free surface bycutting simultaneously two ropeson the droppingtower.The experiment scheme, dropping test byfree fall entry, is illustrated in Figure 2. The time during the dropping process, from the beginning of the dropping the ship model until hitting the water- freesurface, isrecordedusingacamera.
ts = 0 sec ts = 0.42 sec ts = 0.45 sec ts = 0.50 sec
ts = 0 sec ts = 0.40 sec ts = 0.44 sec ts = 0.50 sec
force measurement device. By pressing the piezoelectric knock sensor,force N working on the sensor is shown in the measurement device.Then,the impact pressure (Pa)isdefined by multiplying the digital numberwith force per digital number which is divided by the section area of the piezoelectric knocksensor.
3. Results and Discussion
In this present study, the dropping test of the ship model was carried out successfully, and the experimental data were obtained.Then,the obtained results have been discussed accordingly.Figure5shows examples of the snapshots of the ship modelduring the droppingtest. Thebow of the ship in bothimpactangle hitthewaterfree surface. In the case ofthe weight ofshipmodel 2.42 kg, the vertical velocityof the ship after dropping the ship model until reaching the water-free surface in both impact angles 0° and 10° is about 0.40
m/sec.
Based on Figure 5, the water splashing occurred, and then the characteristicsofthewatersplashingfor both casesseemedsimilar. In othercases, theshipbowwith theimpactanglesof 20°and30°was suddenly lifted upward after the entry process, and then the ship capsized. This occurrence happened ina relatively short duration. Furthermore, the ship model with bow angles 30° experiencedan occurrenceof the wet deck during entering thewaterfreesurface.Regardless, the slamming induced impact pressureon the occurrence was still measured.The time historiesof the impact pressure in each model weight for the weight model of 2.42 kg and 7.29 kg are shown inFigure6. In the hydrostaticconditions,for the weight model of 2.42 kg, thepressure is actingonlyat impact points SI and S2,and each impact pressure isless than 20Pa.
f A 11
T”350
'4
a).BowAngle0°
A EBFi
b). Bow Angle10°
Figure5.theSnapshotsoftheModel Withinthe Dropping Test;a).BowAngle0°,b).BowAngle10°
In thedropping test,the peakpressure at impact points SJ, S2, S3, S4,for theimpactangle0°, is253.298Pa,235.673Pa, 212.048Pa,189.611Pa,respectively.Astheinfluence inincreasing the impactangle, the peakpressuredecreases.Also,the vertical positionof the impact point in the bow flare affects impact pressure. When the impact point is reached by water impact increasingfrom baselinetotheimpact point again,the impact pressurealso decreases. Thisimpactbehavioris the sameas in othercases.Furthermore,the other cases are shown inFigure 6a andTable 2.
Meanwhile,the peak pressureat impact points (SI,S2, S3,S4)for the impact angle0°and themodel weight 7.29 kg as shown in Table2are 853.298Pa,773.298Pa,683.298Pa,599.611Pa,respectively. Figure 6b shows the time historiesof the impact pressure at each impact point in increasing the impactangle.The impact pressure decreases steeply in a short durationfor allimpactanglesafterreachingthe peakpressure. Thevertical velocityisabout 0.28
m/sec.
Asthe comparison results,the discrepancyof the peak impact pressure between ship model weight of 2.42 kg and 7.29 kg for the impact angle 0° is 70.36%S/,69.52%S2, 68.97% S3, and 68.34%S4. For the relative impact angle of 30°, the discrepancy is 67.02% SI, 65.73% S2, 58.51% S3, and 48.21%S4.Plowever,thedroppingtestfor the relativeimpactangles20°
and 30°experiencedabow diving phenomenon,and then theship modeldidnot returnto itshydrostatic condition.
The tendencyof peak pressure in increasing the impact angle is similar for all impact points, as shown in Figure7.For theship model weight 2.42 kg, the peakpressure decreasesrelatively smallmagnitudefromthe impactangle0°to 10°, and then it tends to decreasesteeplywith thesignificant valuefrom10°to30°.Forthe peakpressurefrom theimpact pointto another impact point,the discrepancyof the peak pressure is relative in the same value from SI to S2 along increasing impact angle;however,it is different from S2 to S3 and S4as shown in Figure7a.Onthe otherhand,the peak pressurefor the ship model weight 7.29 kg decreases relatively with the same value in each increasing impact angle as shown in Figure 7b.
ρ ρ
-10 40 90 140 190 240 290
0.420 0.440 0.460 0.480 0.500 0.520 0.540 0.560
Pressure (Pa)
Sensor 1 Sensor 2 Sensor 3 Sensor 4
-50 150 350 550 750 950
0.270 0.295 0.320 0.345 0.370 0.395 0.420 Sensor 1 Sensor 2 Sensor 3 Sensor 4
-10 40 90 140 190 240 290
0.420 0.470 0.520
Pressure (Pa)
-50 150 350 550 750 950
0.270 0.295 0.320 0.345 0.370 0.395 0.420
-10 40 90 140 190 240
0.420 0.470 0.520
Pressure (Pa)
-50 50 150 250 350 450 550 650
0.270 0.295 0.320 0.345 0.370 0.395 0.420
-10 10 30 50 70 90 110 130 150 170
0.420 0.470 0.520
Pressure (Pa)
Time (sec)
-50 50 150 250 350 450 550
0.270 0.295 0.320 0.345 0.370 0.395 0.420 Time (sec)
Jurnal
0° 0°
10° 10°
20° 20°
30° 30°
(a) (b)
Figure6. theTimeHistoriesofthe ImpactPressurefor Model Weightat Sensor Pointand RelativeImpactAngles;
(a). Model Weight 2.42 Kg, (b). Model Weight 7.29 Kg Table 2. the Peak Pressure atImpactPoint
Model
weight (kg) angle (°)
Relative impact Peakpressure(Pa)
SI S2 S3 S4
2.42 0 253.298 235.673 212.048 189.611
240.673 218.611 199.245 179.312 187.925 165.676 154.239 144.167 160.051 137.802 129.177 121.928 853.298 773.298 683.298 599.611 760.333 669.611 580.245 499.303 585.877 502.412 401.111 297.881 485.288 411.143 311.312 235.411 10
20 30
7.29 0
10 20 30
The impact pressureinassociationwith theimpactvelocity and impact point positionon thebow flare,theimpact pressurecan be characterized by using the coefficient of the peak pressure. The peak pressure coefficientCpisdefined by
Pmax/0.5
Vi2,wherePmax is the peak pressure, is thewater density, and Vi is the impact velocity reaching the impact point after hitting the free-water surface. The vertical velocity ofthe shipmodel to thefree-water surfacegeneratesthe impact velocity reaching the impact point within bow entry. The impact velocity is obtained ina short time. The impact110 130 150 170 190 210 230 250 270
0 10 20 30
Peak pressure (Pa)
Relative impact angle (°)
Sensor 1 Sensor 2 Sensor 3 Sensor 4
110 210 310 410 510 610 710 810 910
0 10 20 30
Peak pressure (Pa)
Relative impact angle (°)
Sensor 1 Sensor 2 Sensor 3 Sensor 4
0 0.2 0.4 0.6 0.8 1 1.2
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
Cp(Pmax/0.5ρVi2)
Vertical distance impact point (m)
0 degree 10 degrees 20 degrees 30 degrees
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
Cp(Pmax/0.5ρVi2)
Vertical distance impact point (m)
0 degree 10 degrees 20 degrees 30 degrees
pressurecoefficientforthe impactangle0°andship model weight 7.29 kgishighest inincreasingbow immersed.
(a) Model weight 2.42 kg (b) Model weight 7.29 kg
Figure7.the Tendencyof Peak Pressure due to Model Weight in Increasing the Relative Impact Angle
Theoverall resultof the peak pressure coefficient for the model weight 7.29 kg, as shown in Figure 8b is higher than theship model weightof 2.42 kg, as shown inFigure8a.Basedon Figure 8,the peak pressurecoefficientsduetothe ship modelweightof 7.29 kg inthe impact point SI (nearestbottompart) are higher than 1.0 for allimpactangles,andthere are two peak pressurecoefficients due to the weightof 2.42 kg in the impact point SI (nearest bottom part) are higher than 1.00 givenby the impact angle 0° and10°.The peakpressurecoefficient higher than 1.0indicatesthata ship suffers high impact pressure, andthisconditioncanbeaship that leads possibleto damage.
(a);
(b)Figure 8. the Peak Pressure Coefficient in Vertical Distance Impact Point Influenced by the Model Weight;
(a) 2.42Kg,(b) 7.29Kg
Based on thediscussion above, this present resultemphasizes a notable finding that a ship in slammingconditions experiencesthedynamicresponsesof the highimpactpressurein the bottomand bowpartwith a smallimpactangle. The ship withfull loading condition anda small impact angle in the slamming event is also induced by the high peak impact pressure and leads to the most vulnerable damage. Therefore, the ship with full load conditions in slamming conditions has to beanattentionto the ship navigation.Inaddition, theshipexperienceswaterondeck, and thebowdiving phenomenon possibleoccurs when the impact angle becomes larger. Regardless, the bottom and bow parts ofashipshould be designed properlyto reduce impact pressure due toslamming conditions.
4. Conclusion
Theinfluenceof the impact angle in the slammingevent,the peak pressure decreases in increasing the impact angle.
Also,the vertical positionofthe impact point in thebow flareaffects impactpressure induced byslamming.The impact pressure decreasessteeply in a shortdurationafter reaching the peakpressure.Thetendencyof peakpressureinincreasing the impact angle issimilar to actingon the bowflare.
Regarding theeffect ofshipweight, the peakpressuredecreases relatively small valueduetothe smallimpactangle. It tendsto decrease steeply withthe significant value by the high impact angle. The discrepancyof the peak pressure is relative in the same value acting on the nearest bottom part along increasing impact angle, and it is different on the high bow part.
'
" "
“ ”
"
"
"
" –
"
"
" "
"
"
"
"
"
" –
"
"
" "
"
"
"
"
" "
"
"
"
"
Jurnal
Inincreasingthe ship sweight,the peakpressuredecreases relatively with the same value in eachincreasingimpact angle of the bow flare to free-watersurface.
The tendencyof the peakpressurecoefficient in theimmersed bowflareissimilarforany impactangleof the bow flare.
The peak pressurecoefficient tends to decrease actingon bow flare in increasing the immersed bowflare.However,the peak pressure coefficientdecreases steeply and gradually in a small discrepancyfrom the immersed bow flare in the nearest bottom part.
The peakpressurecoefficientduetothe full loadcondition is highestin thenearest bottompart. However,the peak pressure coefficients due to the lightship condition highest in the nearest bottom part caused by the small impact angle. The highest peak pressurecoefficient in thenearest bottom part indicatesthe ship bowsuffers highimpactpressure, and this conditioncan beaship bowthat leads possible to damage.
Thispresentresultemphasizesanotable findingthataship in slamming conditions experiences thedynamicresponses of the high impact pressure in the bottom and bow part withasmall impact angle.Moreover,the ship experienceswateron deck, andthebow divingphenomenon possible occurswhentheimpactangle becomes larger. Regardless,thebottomand bowpartsof ashipshould bedesignedproperlyto reduce impact pressure due toslamming conditions.
References
[1] T. von Karman, The Impacton SeaplaneFloatsDuring Landing, Technicalnote,NationalAdvisory Committeefor Aeronautics,No.321,pp. 309-313,1929.
[2] H. Wagner, Uber Stossund Gleitvergange an der Oberflache von Flussigkeiten, Zeitschrift fuer Angewandte Mathematik undMechanik,vol.12,pp.193-215,1932.
[3] A.Tassin, N.Jacques, A. Alaoui, A. Neme andB.Leble, Assessment and Comparison of Several Analytical Models of Water Impact, International
Journal
of Multiphysics, vol.4,No.2,pp. 125-140,2010.doi:10.1260/1750-9548.4.2.125
[4] H.Luo,S. Wang and C. G.Soares,Numerical Predictionof Slamming LoadsonaRigid Wedge Subjectedto Water Entry Usingan ExplicitFiniteElement Method.Advancesin Marine Structures, Guedes Soares &Fricke (eds), pp. 41-48, 2011.
[5] A. Constantinescu, A. Alaoui, A. Neme, N.Jacques and P. Rigo, Numerical and Experimental Studies of Simple Geometriesin Slamming, International
Journal
of OffshoreandPolarEngineering,vol.21,no.3,pp. 216 224,2011.[6] D.
J.
Veen andT. P.Gourlay, A Combined Strip Theory and Smoothed Particle Hydrodynamics Approach for Estimating Slamming Loads on a Ship in Head Seas, Ocean Engineering, vol. 43, pp. 64-71, 2012. doi:10.1016/j.oceaneng.2012.01.026
[7] S.H. Kwon,Y.
J.
Yang and H.S. Lee, Experimental and Numerical Study on Slamming Impact,Journal
of OceanEngineering andTechnology, vol.27,no.1,pp. 1-8,2013.doi:
10.5574/KSOE.2013.27.
1.001[8]
J.
H. Kimand Y.Kim, Parametric Studyof NumericalPredictionof Slammingand Whippingand an Experimental Validationfora10,000-TEUContainership,Journal
of Advanced Research in Ocean Engineering,vol.1,no.2,pp. 115- 133,2015.doi:10.5574/JAROE.2015.1.2.115
[9] F.Han,
J.
Yao,C. Wangand H.Zhu, BowFlareWater Entry Impact Prediction andSimulationBasedonMovingParticle Semi-ImplicitTurbulenceMethod, ShockandVibration,vol.2018,pp. 1-16. 2018. doi:10.1155/2018/7890892
[10] A.Tassin, N.Jacques,A. Nemeand B. Leble, An Efficient Numerical Method for the Three-Dimensional Wagner Problem, Proceedingof the 25th International Workshopon Water Waves and Floating Bodies IWWWFB,Harbin, China,2010.
[11]
J.
Jiao, H.Ren andC. A.Adenya, ExperimentalandNumerical Analysisof HullGirderVibrationsandBow Impactof a Large Ship Sailing inWaves, ShockandVibration,vol.2015,pp.1-10,2015.doi:10.1155/2015/706163
[12] S. Wang, S. Rajendran and C. G.Soares, Investigationof Bottom Slamming on Ships in IrregularWaves, Proceeding of the 37th International ConferenceonOcean,Offshore and Arctic EngineeringOMAE,Madrid,Spain, 2018.
[13]
J.
Jiao,Y.Zhao,Y.Ai,C. Chen andT.Fan, Theoretical and Experimental Studyon Nonlinear Hydroelastic Responses and Slamming Loads of Ship Advancing in RegularWaves, Shockand Vibration, vol.2018, pp.1-26, 2018.doi:10.1155/2018/2613832
[14] T.Truong,N.Repalle,F.Pistani andK.Thiagarajan, An Experimental Study of Slamming Impact During Forced Water Entry, Proceedingof the 17th Australian Fluid MechanicsConference, Auckland, New Zealand, pp. 1-4,2010.
[15] F.
J.
H. Huarte and D.J.
M.G.Gharib, Experimental Investigation of Water Slamming Loads on Panels, Ocean Engineering,vol.38,Issue 11-12, pp. 1347-1355,2011.doi:10.1016/j.oceaneng.2011.06.004[16] M. Nikfarjam, O. B.Yaakob,M. S. Seifandj. Koto, InvestigationofWedgeWater-EntryLinder SymmetricImpact Loads byExperimentalTests, Latin American
Journal
of Solids andStructures,14, pp.861-873,2017.doi:10.1590/1679-
78253315
[17] H.Shin,B.Seo and S.R. Cho, Experimental Investigation of Slamming Impact Acted on Flat Bottom Bodies and Cumulative Damage, International
