Numericals studies for the calculation of wave resistance for fishing vessels

Conseil national de recherches Canada

institut de

dynamique marine

SYMPOSIUM ON

SELECTED TOPICS OF

MARINE HYDRODYNAMICS

St. John's, Newfoundland

August 7, 1991

NIJMERICALS STUDIES FOR THE CALCULATION OF WAVE RESISTAJICE FOR F1SHnIG VESSELS

CatiaaI S.M.), GOrt O.(2), McGreer D E.W

(1)i'iaty of British Columb. '4echanical Engineering Deparmeez. Vancouver B.0 Canada. (2)Technical (Jnivery o( Istanbul, FxuIty of Naval Athitecne. Turkey.

canadi

-,--_-

--Zt

1+

National ResearchCouncil Canada Institute for Marine Dynamics

I

INational

Canada Research Council Institute, for Mari,e

Dynamics

Conseil flati haJ de recherches Canada

Institut de dynamique marine

SYMFOSIU ON

SELECTED

_{TOPICS OF}

MARl.

_{HYDRO DYNAMIC}

_S

St. JOhn's, Newfound1aid

August 7, 1991

NUMERICALS STJDIES FOR THE CALCVL4TION OF WAVE_{RESI TAJVCE FOR}

flSHD4G VESSELS

Calisal s.iit(1), Goreti o.(2),_{McGreer D E.(1)}

(l)iiersity of British

_{Columbia, Mechanical Engineenng}

Department, Vancouver BC Canada. 2)TechnjcaJ Univessey of Lsiaflbul, Faculty of Naval_{ArchiLecuge, Turkey.}

ABSTRACT

There are Various methods ailable _{to navaj archiiecas en} p fuel eflictent hull forms. Some of these methods_{are empirical} and some of the newer _{ate nwnericaj. In des en} oe the fuel efficiency of ('tmidJmi fishing_{vessels a sysiestnt*} ies (UBC Series) for fishing _{with large beain-to-imgth}

has been developed using empcal_{method3. This form} further improved by adding side bulbs. The numesisl iodo1ogies used for these studies, their practical _{lisnitacioes and} bsriefltsare discussed briefly. The apicasion of thin ship themyen

ugh Froude numbers and

_{engining resuit.s}

_{Obtained &} Dz,o&s method and a mathematical_{grid generation for this m$w.if}

a

lNTRODUCTON

Harvesting is the most _{intensive pert Of fishi.}

A _{80 percent of the total expc energy as coemi,ned}

iog

pf of the operation. _{These see various reasons forthis, the}

major coc being the fact that (islüng vessels operating in e g see relatively short. less chm _{meters.. and operate se hall}

sp. This gives thou an operalx

_{Weed of the order 10 knea.}

Fseihermrre modem fishing vessels haee a laigth-tobcam ratio al 3

be associated fuel bill is high about_{20(030 Percent of the}

th value. _{And while fishermen see concerned about their fuel}

trnpaon, they also desire to have a large vessel with a lar fish

told city in case they hitthe

big . This is called the

de factor in design, reflecting tha_{owner requirement. For th} ans inshore fishing vessels of Biisish_{Columbia have deveIo}

bouts of large, fuelineffic ion fia.

To respond to the request of _{some fishermen in B.C.,.}

mcthoth to reduce fishing vessel fuel _{sumpcion were studied}

as

S4echaaicaj Engineering Department_{as UJ.C. As part of this 'orka} rnege beam-to-length ratio fishing _{series, UBC Series, has bees}

velopesf and side bulb, and st (airing concepts and

sibiliry for the B.C. fishing flees_{aere tested. The UBC series isa}

le.chincd, fthe

_{.ngle vel series.}

_{Fourteen models}

with venous beam-to.lengtji ratios _{block côefficietrj Were eocd} the B.C. Ocean Engineering _{Center and the results psesiws1}

en

eavaL architects (Calissj, 1990). _{A zence algorithm for the UBC.} us is also given.. Past this phase_{a e bulb concept was ssed.}

The re _{for sides bulb is that the}

Department of Fishies Oceans in Canada_{resuicu the v}

length for licensing _a

proauding bulb is seen as unsuitable net handlin&

There are various proc to estimate ship wave rmcc One such proced is _{on thin ship theory and is not}

y jnstulable for fishing vesad _snetries.

Another phe

4w1 to estimate ship_{wave reuc}

is Dawsons method. TPã

a linear free surface con _{but satisfies exacdy the}

I

condition below the undjg _{free surface line.}

The fug

is used to design side bulbs for the UBC seriesparent baa_{so evaluag}

the reJa _{of different hull krain.} 2'ts obtained and the merits sari _{ujtjes of these methods see}

below.

In addition to numerical_{cakulacions, dsect wave resistance} calculations based on kmgizudina _{wave cuts were used to evaivate}

the change in wave

_{resinc of modified hulls. This}

method was

found to be very useful in eStablishing Which coupens_{of the hull}

resistance has actually changed_{as a result of hull mciificati} THUJ SHIP FORMULATION

This formulation is possibly the oldest _{calculaijon of} ship wave resistance. _{It is based on the}

assimpdca that the hull

waterline slopes and wave slopes_{are small. A per}

tiatioti procedure

linearizes the free siwfxe and hull boundary confltica. _{In addition,} the domain of calculasi, _{is reduced to the sncs}

Occupied by the

undisrn

waler with a cut on the hull center pane. A solution is

obtained by distributing Havelock sources of inzesmy proportional _to

the waterline slope. The_{bull resistance is gives by the well known}

Michell's integral.

This classical formulation _{was modified to a quadratic form} by Hsiung (1981) to find_{optimal bull form. He then}

developed an optimization procedme en solve the quadratic progratmining_problem.

In principle, differ _{sees of constraints could he}

added to the formulatjoe, nath in keeping the aft sections of dm ship or hull

thspIacónentcona

The way this formulation was used for _{BC series with} Wolfe's algorithm was_{reported by Goren (1988). The}

main purpose

as that time was to find the

most suitable forebodies for the IJBC

seres for given speeds and

displacements. Tie U series parent

hull is composed of_{S developable forebody and}

dciubte chine aft

body. _{This form wus found to be more efficient than the}

locally ezisting seine; models. _{The body plan and the hull}

parameters are riven in figure 1 and table I respectively.

Figure 1. Body plan for hybrid Table L Hull Parameters for_{Hybrid Hull}

C, 0.615

c.o.697

L/D. 3.062 3/T-2.48

In the numerical

b0ii the total ship resistance

is

rtpresented by the sum of Michell Integral and the ITrC 57 coerelazion tine. Using ffacat constraints for the hull definitions

and various operar anal for shp speed and displacements virjous (orebodies were The consuaints and the results

ate outlined below. Basic constraints nsed

a-All the unbiown o5 are less than or equal to the half beam.

b-The ongilial offsets Cl ship are tskcn as the lowe2 boUnd of

the unknown offsetL

c-A masimum waLesie shçe is ass gned.

d.The.wazer plafle aren is flied as the design waterline. e.The midship soction area is fixed.

(- The displaement cal the vassal ii fixed.

A modific i of Lbs IiU for multiple drafts andspecds was

done by miniinising a fr!iei.r5 coefficient the weighted

resismnce coefficients

_{citions. Tha is physically}

equivalent as the mrn - _{Cl the total wait done dining a} fishing uip (Goren. l9)..

his computer ogra de'Clcped fcx this purpose was fuss used

to calculate the Micheil i' values tot the Wigley hull and

the Series 60 block 60. While the results the (or Wigley hullwere

rather good, the results ks Series 60 showed relatively poor

correlation with the _{sice curves available. This is, of} course, not surprising.

After the pteIimina cas. the MICIICU ifliegral values toe

the UBC ies paent bull e calculated ignoring the fact that

these (onus are hardly . The Michell resistance value tar

the UBC parent hull for Fs _{numbers around 0.35 was found to} be comparable in _{ni1ta the experimental residual resistance}

values. This is rather but a foruMiare correlation for this

wait

The variable offsets I _{opcimizaeiOo corresponded to the first} three stations of the hUfl sied by 10 stations. A fiveperceflt

increase in the forebudy _{e was also permistert A design}

speed of 10.5 knots w chc _{for the single Weed operation of a}

70 ft vessel The _{of the models was Mieaswed ax thC B.C.}

Ocean Pñgiwiing C.

The flr _{bulb was dgmid so diat the maxinium waterline slope}

would be les3 than 26 _{The forward block coefficient was}

allowed to increase by iwa ps and the offsets

as stat on two

were to be less then 0.335 es the macithum offset.

The resulting bu.. BULB

I (Figure 1). achieved a theoretical teducuon in uJ esissonce of the order of 16.8 percent at

the design speed.

Ftgxie 2. Bulb_I

10

A _br

BULB 2 (Figure _{3). was designed for}

the

some design speed has

with slightly modified conssraj _{For this} bulb offsets as

0.5 and I were required to haves valuelarger

han 80 percom & _{ur original value, and the}

offsets at atadon 2,90

pezcem of the origiasi

value. The other_{Constraints remained as listed} above. This bulb

a theoretical reduction_{of 16.5 percent of} the

total resistanen. The

cxperimel value (cs the

_{reduction in total}

res _{was 18}

at the design speed (Figure 4).

Figure 3. Bulb 2

CTP! HORSQW3

I

I

-

bs

Figure 4. Cnuparn

of EHP for Bulb I ,BuIb 2 and parent hull.

gUre5.Bulb4

The optimization _{at multiple draft operations}

_qáj

vnJ _{as weighting factors. These values}

were nliz

asS(ora105(oodratat9otaandO4Sfg

11 woes. This is meant to represent travel to fishing

li _{cition as a relatively high speed}

and a return wü

'

displacement and as a relatively lower

_{speed. The piti}

ss

_{reductions were 12.2 percent (or a 10.5}

diat 10 biOct and 8.6 percent (or_{an 8 foot draft as 11}

T

pts

average reduction in EHP for _{the specified opero}

as

asnJ4e drafu and speeds_{was 10.4 percenL Tank}

reealt owed

as be effective as both _{operaiio ions}

ith a the

g-

_{in EHP of about 10 percent (Figure 6). However,}

bow w _{W$ observed to break at low draft,}

pOsibIy as a resela of

vewajnn this region.

8E 9U2 DEONED

_{R V#1O RAFTS}

0

00

0.2 0.4 O.s O.

FROUDE NtflsBzR

Figure 6. Comparison of EHP for Bulb 4 and parent haL

The thin ship formulation_{was also used for the esrimas}

al

we ressance of a high imgth-so.b _{mono hull form by Cast}

(11). The length.so-b

_{ratio for the model in}

qurmion

Ii

the model name LBII. The _{length of the model}

_Ied

4.3 _{ft .beam 0.43 ft,draft 0.18 ft and the displacemem}

13.4 lbs.

wave resistance was obtained by calculating the

_{_ field}

wave posentiaJ using an asymptotic form given by tlrsefl_{(1960) aed}

by i ogrant of longitudiflal wave

cut method (Causal, 1976). The

thur ship resistance

compwaucn by the above method _{d the} ezerimental wave cut and_{res dual resisctnc values are gi}

in

flge 7.

The form of the chree-dimeiisj _{wave form pectct}

by _{ie thinship formulation is given}

in figure 8.

Figure 7. Residual and wave resistance_{curves for LBIL}

The ncndimensjoonj numeijc2j_{wave re}

of the model

showed a trend similar so the _{asper 1entaIjr otmei values}

using

wave height data for Froode _{numbers larger}

0.& For F,ou

numbers less than 0.5, however,

_{the dif(ee hetwu}

the residual and nUmerical values_{was much larger thee eeiej}

For Froode

nwnbers larger than 0.8 the_{numerical and 'esidiasi}

values were observed so be vmy close,

_{possibly sutàig}

anme of the assumptions used in the thin ship theory are much be _{musfied in} thiS rangeof Proude numbers. Figure 9 gives the

_varn

_{o(the free}

wave ampliuC spectra as different Froude mubess.

MODEL L811 AT Fn - ø.64

Al X-I vr i,

ee.ee ot:

_{oc:r4I* X.}

;

Ac.JAT:36

. Z VQ.s trCJi si . . 35 13

vRtc.I1.. rcA: :

rRAMs SCALXPG_{IVE 3ATT4} 4. 1

_tsc

Figure 8. Three Dumjj

_{View of Nume}

Panem for LBII azFo=0443 0.3 LECEND C F

-I _Tn -I

-L!

L

.4

0.0 !.5 20 2.5 3.0 3.5 NON _1ONAL TRAJseyrjs

Figure 9. Variation of_{Wave Spectra as high Froude}

DAWSONS METHOD

Dawsona (1977) method has a nWnerical free surface ticn and setisfies the hull boundary condition on the bull. This ' has been well ied and was modified to beadle transom

"--'1989) lt of the new fishing vessels

gned in B.C. stern

condition is different than for the dry uansom s of Cheng. Maiananeuvc (1989) k1 a numerical model for wet aaisome

and this was used in these studies. Dawson's method that the

ull and a portion of the free surface is represented by a grid. A double-model potential is calculated first, then a pera on this

potential is calculated.

A free surface condition is obtamed by eeglecung and higher otder terms in perturbation potential arid differentiating along the eam1iiies This of cow generates an

tk-M problCm as the aneamlines have to be wo before a crical free surface condition can be applied. A fair- point

bew2

differentiation of D*won satisfying the ri1wl condition is med in the calculations. Once the panel sow strengths are

known. the kinematic valme and the pressure, are obned. The hull

resistance, which in thiS is the wave resistance, is obtained from

the integranon of the pree on the we1ed surface in calm water.

Shipe with a transom stern have to be treated in_{a diffáent way.}

Maiscineuve assigns a fluid velocity equal to the sh1 _{velocity on}

the panels immediately _{isream of the vansom, ilying that the} hull exsends to infinity and that the local waves are negligible.

NUMERICAl, RESULTS WITH DAWSON'S METHOD

The weakest linkrn the_{procedru is the}

MiOfl of the

stream1ine. In most of the wait done_{at UBC we the stream} lines for the double model solution as the stream li _{on the free}

surface. _{Recently, however,}

a new procedure has' _developed

along the grid generation

procedure o(Aflieyj (1990). Tb _procedure have been applied to the

wave resistance estimation of_{the Wigley}

hull and am currently being applied to the LJBC series _{hulls. One can} see

_{in figure 10 that the}

mathema _{generation of the grid} consistently improved the_{predictions. The results wtha 12x44 mesh}

is rather promstng.

This mediod managed to show a hump at Froude number 0.32 while the previou method using the_{double model does}

not show a distinct hump as that Froude number. At higher

_Frodc

numbers the double hull

streamline method using 34x lOpanets on the free surface gives values less than the experimental _{values while the} mathemarie _{streamline miod using 9x33}

or 12x44 _{hes give} wave resiswice values clo _{to the experimental averages.}

In the case of transom sternsat i _{four streamlines seem to be necessary} for _{engineering accuracy.}

In general the panels behind_{the Stern}

should extend at least_{halt a wave length aft of the ship}

The length of the panelled region ahead of the ship must be _{about a quarter ship}

length. The width

of the paneled region of the free sur should be at least half ship length.

Wts fl..._ Wy Ii

S 4 $ a S

sne one one one

p.

_one

Figure 10. Effect of Grid on Wave Resistance f _{Wigley huh..}

12

The application of the program to Pacific seiners with transom

erns is given in figures 11. for the USC series Parent_{Hull. In}

addition, anoc _{fishing vessel KYNOK was studied with this} program. _{The results for wave resistance are given in figures 12.} Another _{interesting restilt}

_{one can}

_{chum from}

Dawsocs

formulation is the estimation of wave profiles along the hull, as well as, sinkage ar _{trm. The sinkage calculated for KYNOC is given}

in figure 13 _{comparej to experimental results. Most of the}

numericaj results followed the experimental ucad.. ThCIt accuracy. however, is _{erJmes less than normally required for}

gineering applications.

Figure 11. Wave Resistance prediction by Dawsoc's mCthod for.

USC Patent Hull.

g 3.I

I

uric Ptic 11.1 Wau

XYNOC Ill, Ww '*

an-ns 0.2. 0.3

Figure 12.Wave Resistance Prediction by Dawson's Method for

KYNOC

The velocity vectors at 25cm away from the center plane for Kynoc as _{6.1, biois axe given in figures 14. We have no} experimental values with which to compare the velocity vectora, but

the information on the flow lines could _{be used for a variety of}

Figure 13 Sinbgc for_KYNOC

A calculation of the wave profile away from_the

_veJ

_{was also} aapcet The results of this calculation is_{given in figure 15. ft}

aw

thai this calculation pvc a wave reflec _{from the grid}

bcxsoday. This might be interpretedto mean that Dawsons method

is an inner solution and a ecinl technique suchatd of Nobless (1990) is necessaty to obtain the_{outer solubon.}

FI

ijId Arjn

_{.nOC ot 8.2 Knots}

25 c _{c.o- Ct,,-i.n}

- d frcun UOC Sii.

_Ni

-a a-as as

s's

9

Figure _{14 Flow Lines, by}

son's Method for KYNOC at

Figwe 15 Far_{Field Wave}

P bulL by "ons Method (or

Our expenz

ng Dawson's method with fishing veSsels

suggests that g values for cunparative evaluation of hull loans, wave proliles along lIz nIUinkage and trm. and possibly velocity ors in close

_{oiicy to the hull can be}

calculated Cven f

'

els'with a ran stern.

coNauslc

The expenzt at IIBC tizwed the. the methods available for the calculation of _{p wave resistance can be used to design fuel} efficient hull ftas even for low length-to-beam ratio vessels such as fishing vessels. The aitical

_{seem to be the}

constraints imp by the user.

Thin ship theta7 gives wave resistance values comparable to the experimental resi resistance values kr kigh length to benni ratio vessels at a Fro ber range larger ntn 0.8.

Dawson's mcd is found to be l establishing-near field

solution. This permits calculailon of the pressure vanation along the bull, and Of 'velocity vectors ii dose proximity to the hulL

Dawson's method gives wave resistance values comparable to the experimental retil rstance values, even for wet transomstern

hulls, and could be umd to predict eng..eug values of interest_to

designers.

AaaowLEDc9.cNT

The author 'onld like to thank NSEC, NATO and DFO,

EMR. Canada for supporting different aecraOfthe research reportCd a thiS p3per.

REF

Allievi A., Causal SM. AppIrrir. of Bubnov.Galezlcin Formulation to Grthogciial Grid Gciiàzkm to be published in J.

Computational

Physica..-CIkj

.S.M McGrcer D. E., Ycdd Resistance Tests of_a Systematic Series Of Low LJB Vessel?. _{Spring Meeting of the}

Pacific Northwest SeitirmOf_{SNAME. Vccrie May 1990. AcceptCd}

for publication in Marine Thnolo.

CaUsal SM. 'A CaIcitlazii of the Free wave Spectrum for_a Ship'Report No EW-lO-76 Naval Systems Daparunent Division _Of

Engineering _{and Weapons, U.S. Naval Academy Mnapolis,} Maryland 1976.

Cheng. H. Compwaticn of 3DT _{Stern Ftows 5th}

International ConL on Numetical Ship Hyrodvnamics, Japan. _1989.

Dawstin. C.W. A Pi'actical Copuen Method for _Solving Ship-Wave Problem? Proc. 2nd Conf on Nutherical Ship

Hydrodynamics 1971.

Hsiung, CC. 'Optimal Ship Puns for Minimum Wave

Resistance', J Ship Rch Vol 28. No 2. Jane 1981 pp 96-116.

Goren 0. Cthsal SM. 'Opdmti RmIl Forms for Fishing' Vessel?. STAR S)'..yos.um Pittsburgh Pmaylvania_{pp 41-51 June}

1988.

Clark B.C. Wave Resistance Of Hlgb Length/Beam Mono. hull Ship? Master ci Scinice Thesis Ua.y Of British Columbia

March 1991.

Maisonnenve, LL 'Resolution da Pmbkrne de Ia Resistance de Vagues de Navues pa' Line Methode da Singularites de _Rankine'

Doctoral Thesis, U ciNantes, 1989.

Nobless F. Lin W2,t Mellish R. 'Anatjve Mathemazjcsj essions for the ady Wave Spewu

_{of a Ship* I. Ship}

Research V.34 No 3 Sq* 1990 pp 149-162.

Ursell F. _{Kelvin's Ship Wave Paiseni' I.}

_fl

Mechanics V.8 pp 41$-431. 1960.