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1 INTRODUCTION
Shiphandlingandmanoeuvringisdefinedastheact
ofpropercontrolofashipwhileunderway,especially
in harbours, around docs and piers, or restricted
waterways. All ships experience air and wind
resistancewhileunderway ofsea,inharboursorin
limited waterways. The environment surrounding
a
ship have a significant impact on ship resistance.
When the ship navigates within harbour wharfs or
approachingtheberth,thewindisoneofthebiggest
environmental factors effecting a ship. The wind
resistanceonashipisafunctionoftheship’swindage
area,windvelocity,anddirection
relativetotheship’s
heading.Inseapracticethepressureofwindonship’s
superstructure is definedas the wind forceper unit
area. This force has units of tonnes and uses the
simplified formula to multiply the wind pressure,
expressedintonnespersquaremeters,bythe ship’s
windage area,
expressed in square meters. When
operating the traditional cargo ships, the windage
area depends on ship’s draught and distribution of
cargoondeck.Specifictypesofships,likecarcarriers,
passengerships,Ro‐Ro/passenger/trainshipshavea
hullconstructionsgettingthousa ndsofsquaremeters
of the windage areas. The
safety of port
manoeuvrings of the above ships is associated with
negativeeffectsofwindpressureforceonship’shull
and superstructure. The basic model of Ro‐Ro/
Passenger ship superstructure for calculations and
analysisofthewindinfluencewhenmanoeuvringin
harbour,isshowninFig.1.
Figure1. The basic model of ship’s superstructure for
calculationofwindpressure.
Some Effects of Wind on Ship’s Manoeuvrabilit
y
M.Szymoński
PolishNavalAcademy,Gdynia,Poland
ABSTRACT:Allshipsexperienceanairandwindresistancewhileunderwayofsea,andtheymayexperience
adverse effects on wind while manoeuvring in harbours and limited waterways. The wind resistance is
proportionaltorelativewindspeedsquared,winddirectionandtheprojectedwindagearea
oftheship.The
paperdescribestheeffectofwindpressureintotheship’ssuperstructuresandhousesonshipmanoeuvrability,
intherangeofthewindspeed,fortheshipwhichiswiththe large windage area. The above is one of the
recommendedinformationtobeincludedinthe
ship’smanoeuvringbooklet,asperIMOResolutionA.601(15).
In sea practice, the manoeuvring characteristics in wind, as wind forces and moments, course‐keeping
limitation,anddriftingunderwindinfluencearefarefromtheseestimated.Theresults obtainedduringthe
severalyearsofpracticeinship’sexploitationareincludedinthispaper.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 13
Number 3
September 2019
DOI:10.12716/1001.13.03.19
624
The above model of the ship’s superstructure is
created on the base of real Ro‐Ro/ Passenger/ train
ship with the following main particulars, shown in
Table1.
Table1.Mainparticularsofpresentedship.
_______________________________________________
GrossCapacity32000RT
Maximumdisplacement18107T
Deadweight6855T
LengthOverall169.9m
Breadth28.0m
High42.3m
Maximumdraught6.2m
_______________________________________________
2 ANALYSEOFVERTICALMOMENTSDUETO
WINDPRESSURE
The model of ship superstructure, described in this
paperhasahugepartofship’shullabovethewater
level. For maximum draught, just 6.20 meters of
wholeheightoftheship’shull,issubmergedofwater.
At the same time
36.1 meters of the whole ship’s
heightisabovethe water level. This case presents a
good example of wind influence on a ship
superstructureduringthemanoeuvringsinrestricted
watersinsideharbours.
Thefollowingtablescontainthecalculationsofthe
windage areas and moments of wind pressure force
on
theshipforvariabledraughtsofanalysedmodelof
aship’ssuperstructure.
Table2. The results of wind pressure force for draught of
5.00m.
_______________________________________________
MOMENTDUETOWINDPRESSUREFORCEFOR
Draught:5.00m
_______________________________________________
Item Area Wind Wind VCG Vertical
pressure forcemoment
m²N/m² Tonnes m Ton.m
_______________________________________________
Areano.1 1486.80 120.00 18.19 8.08 146.95
Areano.2 1533.30 120.00 18.76 18.15 340.42
Areano.3 148.80 120.00 1.82 28.20 51.33
Areano.4 286.50 120.00 3.50 26.06 91.33
Areano.5 50.50 120.00 0.62 26.60 16.43
Areano.6 194.50 120.00 2.38 3.10 7.38
_______________________________________________
Windage 3700.40 120.00 45.27 14.44 653.84
area
_______________________________________________
DISPLACEMENTFORDRAUGHT5.00m 13667.00Tons
_______________________________________________
The single areas, as a basic elements of complete
windage area of the analysed ship’s superstructure
arepresentedinFigure2.
Figure2. The elements of ship’s windage area, as per
calculationsmadeinTables2‐4.
Inrealconditionsthewholewindageareaisgoing
to be calculated as the sum of several geometrical
areasoftheshipsuperstructure,and,inmanyreasons
also the cargo on deck. The above effect has been
puttedonviewinpresentedTables.
Areano.1reflectsvolumeofthemainship’s
hull,
anddoesnotdependondraught,keepingthevalueof
1486.80 square meters. Areas from No. 2 to No. 5
correspond the ship’s superstructure as
accommodations, and cargo decks (areas no. 2 and
No. 4), navigation bridge (area No.5), and funnel
(area No.3). The above areas have got still
the same
volumesof1533.3m²,286.5m²,50.5m²,and148.8m²,
respectively.Onlytheareano.6changesitsvolumein
function of the ship’s draught‐from 194.5 m² for
draught 5.00 m to 0.00 m² for maximum ship’s
draughtof6.20m.
Table3. The results of wind pressure force for draught of
5.50m.
_______________________________________________
MOMENTDUETOWINDPRESSUREFORCEFOR
Draught:5.50m
_______________________________________________
Item Area Wind Wind VCG Vertical
pressure forcemoment
m²N/m² Tons m Ton.m
_______________________________________________
Areano.1 1486.80 120.00 18.19 7.83 142.41
Areano.2 1533.30 120.00 18.76 17.90 335.73
Areano.3 148.80 120.00 1.82 27.95 50.87
Areano.4 286.50 120.00 3.50 25.81 90.45
Areano.5 50.50 120.00 0.62 26.35 16.28
Areano.6 112.60 120.00 1.38 3.10 4.27
_______________________________________________
Windage 3618.50 120.00 44.27 14.46 640.01
area
_______________________________________________
DISPLACEMENTFORDRAUGHT5.50m 15434.00Tons
_______________________________________________
Itshouldbenoted,thatincaseofpresentedtypeof
ships,likepassenger ships, or Ro‐Ro/passenger/train
ships, the draught is acting on windage area in
limitedway.Incaseofpresentedmodel,thewindage
areavariesfrom3700.4m²to3505.9m²,causingvery
smalldifferenceof
2.38tonsinwindforcepushingthe
ship.
The difference in windage areas:ΔA = 194.5 m²
multipliedbywindpressureP=120N/m²,andafter
that,dividedbythegravitationalaccelerationof9.81
m/s², is giving the value of wind force of 2.28 tons
only.
Theaboveisthe
proof,thatincaseofshipswitha
largewindage areas, getting of severalthousands of
squaremeters,theincreaseinship’sdraughtdoesnot
transpose in reduction of wind force or vertical
momentofwindpushingtheship.
When changing the draught, the different
moments of the wind pressure
force has to be
appeared. The said effect is described in Table 2 for
the ship’s draught of 5.00 meters, in Table 3 for the
ship’sdraughtof5.50meters, andinTable4forthe
ship’smaximumdraughtof6.20meters,respectively.
625
Table4. The results of wind pressure force for draught of
6.20m.
_______________________________________________
MOMENTDUETOWINDPRESSUREFORCEFOR
Draught:6.20m
_______________________________________________
Item Area Wind Wind VCG Vertical
pressure forcemoment
m²N/m² Tons m Ton.m
_______________________________________________
Areano.1 1486.80 120.00 18.19 7.48 136.04
Areano.2 1533.30 120.00 18.76 17.55 329.17
Areano.3 148.80 120.00 1.82 27.60 50.24
Areano.4 286.50 120.00 3.50 25.46 89.23
Areano.5 50.50 120.00 0.62 26.00 16.06
_______________________________________________
Windage 3505.90 120.00 44.27 14.47 620.73
area
_______________________________________________
DISPLACEMENTFORDRAUGHT6.20m 18107.00Tons
_______________________________________________
3 SOMEMANOEUVRINGCHARACTERISTICSOF
SHIPUNDERTHEWINDPRESSUREFORCE
The manoeuvring particulars of presented
superstructure model of Ro‐Ro/passenger/train ship,
showninFig.1,hasbeendescribedinthisparagraph.
Discussion about some effects of wind on
manoeuvringinharbourhasbeenlimitedtothestage
oftheberth
approaching.Thistypeofshiphastobe
preciselydirectedintotheindividualbed,where the
ship’srampisboarding.Whentheforcefromthegust
of wind is greater than the ship can immediately
absorb, the berthing operation is dangerously
disturbed.
Whenthewindblowsagainstthesideof
theship,
the bow tends to turn slowly down the wind. The
ship’shullhavelesslateralresistanceunderwaterin
bow side than in stern. When the wind blown
sideways,thebowandsternresponddifferently.The
bow and stern thrusters are designated for pushing
theshipagainstthewind.
The thrusters effects of presented ship’s
superstructuremodelaredescribedinTable5.
Table5.Ship’sthrusterseffect
_______________________________________________
THRUSTER kW Time Turning Time Not
[HP] delay rate delayeffective
forfull atzero forreverseabove
thrust speedfullthrust speed
[sec] [deg/min] [sec] [kt]
_______________________________________________
STERN 1600 7 37148.0
[2176]
BOW4800 7 65148.0
[6528]
BOW6400 7 81 148.0
&STERN [8704]
_______________________________________________
(documentationofRo‐Ro/passenger/trainship)
To compare the manoeuvring characteristics of
presented Ro‐Ro/passenger/train ship, the following
data, shown in Table 6, should be taken into
consideration.
Table6.Forcesactingonship’shull.
_______________________________________________
Draught Windforceforpressure Bowthrusterstowing
[m] 120N/m² [Tons] power [Tons]
_______________________________________________
5.0045.2784.84
5.5044.2784.84
6.2042.8984.84
_______________________________________________
Figure3showstherelationshipbetweenthewind
pressureontheship’shullandsuperstructureandthe
windforcepushingthesideoftheship.Thediagram
fromFigure 3 can also be used for determination of
safe range of static wind effect against the bow
thrustersofthe
ship.
For described superstructure model of Ro‐
Ro/passenger/train ship, the safe range of the wind
effectundermanoeuvringsisdeterminedas19m/sor
8°B,whenbowthrustershastobeused,only.
Inrealconditionsofportmanoeuvrings,notonly
static but lateral force caused by a sudden gust
of
wind is exerted on the ship (dynamical). The
dynamical wind effects has to be important factor
interrupting ship’s manoeuvring when approaching
theberth.
Figure3.Therelationshipbetweenwindpressureand
ship’sbowthrusterstowingpower.
Severalpublications(AzadA.K.,AlamM.M.,2010;
Civitan L.,2003; Namkyun I., Van‐Luong T., ) has
presented the results of the dynamic wind effects
researches,namedasthegusteffects.
AzadA.K.&AlamM.M.(2010)suggest,that
the
estimation of the wind gust based on hourly mean
windspeedvalueshasbeeninitiallysuggestedtobe
processedasfollows:
V
G=KGxVmean (1)
where:
V
G–thegustspeed[m/s],
Vmean–thehourlymeanwindspeed[m/s],
K
G–gustfactor,
K
G=1+2.28/[ln(z/n)] (2)
where:
z‐heightabovesealevel[m],
626
n‐the roughness length ( 2‐9 ) which depends on
terraincharacteristics.
Asperformulas(1)and(2)thegustspeed,forthe
meanwindspeedof19m/s,willbeequal:
1.7x19m/s=32.3m/s (3)
Havinganexperienceinexploitationoftheabove
ship, there is clear that this type of ships is able to
makeasafemanoeuvringsevenincaseof the wind
gustof32.3m/s.
Whenthewindisblowingwithspeed32.3m/s,the
pushingforceisequal106Tons,asitispresentedin
Table7.
Taking
intoaccounttheeffectofcombinedworkof
bow and stern thrusters of the ship, there is a
thrusters force of 113.12 Tons, directed against the
gust.
Table7.Forcesfromthegustofwindandcombinedworkof
Bow&Sternthrusters.
_______________________________________________
Draught Burstofforceofhigh Combinedbow&stern
[m] speedwind[Tons] towingpower[Tons]
_______________________________________________
5.50 106113.12
_______________________________________________
4 CONCLUSIONS
Duringtheportmanoeuvringsnotonlyboworstern
thrusters are being used, but also the main engines,
poweringthepitchpropellers,andrudderblades.
This wide subject has not been discussed in
presentedpaper.
It is important conclusion that not only analysed
thrusters, but also the propulsion
and steering
machinery are being used to drive the presented
ship’ssuperstructuremodelagainstawindpressure.
Therewasstatedthatthesuccessfulshipoperationsin
restrictedwaterscouldbemadenotonlywhenstrong
windsareblowingwiththespeedgreaterthan10m/s,
butalsoduringtheshort
burstsofhighspeedwind,
called gusts, or strong winds of intermediate
duration,termedsqualls.
In second paragraph it was also proved, that in
case of ships with large windage areas, getting of
several thousands of square meters, the increase in
ship’s draught does not transpose in reduction of
wind force
or vertical moment of wind pushing the
ship.
REFERENCES
CivitanL.2003:Determiningwindgustusingmeanhourly
windspeed.GEOFIZIKAVol.20(5),pp.63‐73.
Nam‐KyunIm,Van‐LuongTran,:Ship’smaneuverabilityin
strong wind., Journal of Navigation and Port Research.
InternationalEdition.Vol.32,No.2,pp.115‐120,2008.
Azad,A.K.,Alam,M.M.:Determinationofwindgustfactor
at windy
areas of Bangladesh. Proceedings of the 13
th
AsianCongressofFluidMechanics.17‐21December2010.
SzymonskiM.,AnalysisandevaluationofManoeuvrability
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MengLongZhou,BinLin,XuZhan,Xiao
FengZang,Peng
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