943
1 INTRODUCTION
Technological development causes a significant
demand for energy. The data from recent decades
have indicated an increased demand for energy fuels.
The costs of transporting liquid fuels resulted in
changes in the means of transport, namely LNG
tankers. A significant change is primarily the increase
in the dimensions of the vessels. The increase in linear
parameters of LNG tankers, and above all their draft,
means that a significant problem to be solved is the
safe under keel clearance, both during navigation and
at anchorage. The need to analyze and determine the
safe under keel clearance, for a given area at different
times of the year is very important. When
approaching a port, a ship is often stopped at an
anchorage to wait for her berth or to wait out bad
weather conditions. Each port has an area designated
by the Maritime Administration of the Coastal State
meant for anchoring ships. The simulation studies
presented the problem of determining under keel
clearance for tankers in areas with restricted depth.
The Baltic Sea itself and approaches to many ports are
areas of relatively shallow depth, while tankers have
a deep draft and it means the necessity to accurately
determine safe under keel clearance both during the
approach and at the anchorage.
2 REVIEW OF THE SUBJECT LITERATURE
The construction and commissioning of the LNG
Terminal in Świnoujście, as well as regular calls of Q-
max LNG carriers evoke the need to acquire
knowledge and to assess the possibility of anchoring
of this type of vessels in the area of the Pomeranian
Bay.
Literature available in Poland on the calls of LNG
carriers at the port of Świnoujście mainly covers
issues related to safe passage through the Baltic Sea,
approach to the port and risk assessment for the
transport of this type of cargo which is presented
below.
Simulation Tests of Determining Under Keel Clearance
for LNG Carrier at Anchorage
P. Mrozowski, H. Śniegocki & P. Wilczyński
Gdynia Maritime University, Gdynia, Poland
ABSTRACT: The article presents issues related to the determination of under keel clearance for LNG carrier at
anchorage. The processes related to the acquisition and analysis of data affecting the safety of anchoring
operations have been presented. The collected data made it possible to achieve the research goal, which was to
assess the variability of under keel clearance in simulated scenarios for various hydro-meteorological conditions
observed in the area of the anchorage. The result of the simulation tests is to identify the risks that may occur
during anchoring of the LNG carrier and the presented issues may be helpful in safe planning of the anchorage
for LNG ships.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 14
Number 4
December 2020
DOI: 10.12716/1001.14.04.20
944
These are studies prepared, among others, by the
team of the Institute of Marine Traffic Engineering
and the Maritime University of Szczecin, e.g.
„Analiza nawigacyjna budowy stanowiska
rozładunkowego LNG w porcie zewnętrznym w
Świnoujściu”,„Ilościowa analiza ryzyka morskiej
części lokalizacji Terminalu LNG w Świnoujściu”,
„Minimalne wymagane parametry podejściowych
torów wodnych do Portu Świnoujście” S. Gucma,
„Inżynieria Morska i Geotechnika”, nr 2/2011 r.
autorstwa S. Gucma, „Ilościowa analiza ryzyka
morskiej części lokalizacji terminalu LNG w
Świnoujściu”, Szczecin 2010 r. (S. Gucma), Rutkowski
G., „Modelowanie domeny statku w procesie
manewrowania w ograniczonych akwenach”,
Politechnika Warszawska Wydział Transportu, Prace
Naukowe Warsaw University of Technology, Faculty
of Transport, Research „T”, Warszawa 2001 r.,
Rutkowski G., „Ocena głębokości północnego toru
podejściowego do portu Świnoujście od pozycji
gazociągu NordStream do terminal LNG w aspekcie
obsługi jednostek o maksymalnych gabarytach-
metody uproszczone” Faculty of navigation, Gdynia
Maritime University. Rutkowski G., „Zastosowanie
modelu domeny do oceny bezpieczeństwa
nawigacyjnego statków poruszających się w
akwenach ograniczonych”, Politechnika Warszawska
Wydział Transportu, Prace Naukowe „T”, Warszawa
2001 r. Warsaw University of Technology, Faculty of
Transport, Scientific Works "T", Warsaw 2001
Rutkowski G., Królikowski A., „Ocena głębokości
toru podejściowego na południe od Ławicy Słupskiej
w aspekcie obsługi jednostek o maksymalnych
gabarytach – metoda rozbudowana". Publikacja w
Zeszytach Naukowych AMW Publication in AMW
Scientific Journals, ISSN 0860-889X, Zeszyt Nr 1 (180),
Str.81-96, Gdynia 2010 r.
The following publications, inter alia, can be listed
in foreign literature, the content of which was taken
into account during the simulation process:
A Guide and in Port Approaches, 3rd Ed, ICS,
1999 r., A Guide to Contingency Planning for the Gas
Carrier Alongside and Within Port Limits, 2nd Ed,
ICS, 1999 r., A Guide to good practice on port Marine
Operation- prepared in conjunction with the Port
Marine Safety Code, 2009 r., Admiralty List of Radio
Signals, Volume 6(2), NP286 (2), edycja 2009/2010 r.,
Admiralty Sailing Directions, Baltic Pilot, Volume I,
NP18, edycja 15/2010 r., Aids to Navigation Manual
Administration, Comdtinst M16500.7A, 2 Mar 2005 r.,
Bridge Procedures Guide, 1998, ICS, Coastal
Engineering Manual – Part 5, August 2008, publ. nr
EM1110-2-1100, Code for existing ships carrying -
Liquefied Gases in Bulk- IMO, Code for the
construction and equipment of ship carrying
liquefied gases in bulk, 1983 Edition Code for the
construction and equipment of ship carrying
liquefied gases in bulk, IGC ; Code 1993 Edition,
COLREG, 1977 with amendments IMO, Critical
Incident Management Guidelines, Volpe National
Transportation Systems Center, 17 April 1998 r.,
Critical parameters for LNG Marine Terminal Site
Selection (OTC 19658 Offshore Technology
Conference, Houston 2008 r.)
The analysis of literature shows that few scientists
and authors of articles have become interested in the
problem of UKC of LNG ships at anchor in shallow
waters. The proposed scope of simulation studies
covers exactly this area of knowledge where little has
been presented so far to deal with the problem of
UKC of a vessel at anchor.
3 SIMULATION RESEARCH
The area of the Pomeranian Bay, No.3 anchorage was
selected for the simulation tests. All tests were carried
out at the Faculty of Navigation of the Gdynia
Maritime University using the NaviTrainer 5000
Professional navigation and maneuvering simulator,
ECDIS Navi-Sailor 4000 systems, the electronic chart
simulator and Model Wizard application (v. 5.0). The
ship model used for the research was LNG carrier
(Figure 1), loaded condition with the following:
parameters L = 315m, B = 50m, T = 12m, without trim.
Ship model particulars are presented in Fig. 2 and
Fig. 3.
Figure 1 Model of LNG carrier used for simulation
Due to lack of precise and up-to-date data on
waves and sea currents occurring in the area covered
by simulation, wave parameters have been calculated.
It should be pointed out that the results of wave tests
available in literature in the considered water area are
characterized by significant differences in the
obtained values of height and direction of wind wave
as a function of wind speed vector.
In the initial simulation tests a comparative
analysis of wave spectrum was carried out for two
models, i.e. ITTC and JONSWAP respectively. The
JONSWAP model was adopted for wind wave
spectrum. The wave height adopted in the settings of
initial parameters should be understood as the height
of significant wave expressed in meters. Significant
wave height distribution was generally prepared for
eight wind directions (N, NE, E, SE, S, SW, W, NW).
In simulation tests the value of 6 m / s was
adopted as the greatest lower bound of wind speed.
The average parameters of the generated waves
were determined for winds (without squalls) of speed
of 6, 9, 12, 15 and 15.1-18.0 m / s every 0.1 m / s and
for 6, 9, 12, 12.2- 15.0 m / s every 0.2 m / s and 15.1-
18.0 every 0.1 m / s.
Kryłów and Titov method was taken into account
while determining the wave parameters for
945
simulation purposes, in particular the height of the
wind wave in relation to the wind speed,
The latter, taking into account its purely
theoretical assumptions, computationally generates
values of significant wave height obtained in the
JONSWAP model for maximum values of wind wave
parameters and for the value of fetch limited case of
wind speed necessary for their formation.
In the coastal zone waves are transformed due to
shallower bathymetry. The calculated wavelength
parameters were transformed, by means of the above
methods, assuming an estimated set of wave height
values for a given wind speed in advance, due to the
occurring phenomenon of refraction associated with
the curvature of the wave crest lines and
consequently the change in phase velocity, and thus
the wavelength,
The model was adopted for regular undulations of
a given direction of wave propagation, of certain
height and period of the wave. The results of
calculations of wave parameters were compared to
the obtained results of research and observations in
the southern part of the Pomeranian Bay, taking into
account refraction and additionally compared to the
analysis of observations of the wave field in the Baltic
Sea used in the expansion and modernization of the
ports in Gdańsk and Władysławowo. The local
bathymetry system affects changes in the direction of
wave radii.
Statistical analysis of data on behavior of LNG
carrier model at anchor was carried out on the basis
of simulations performed and discussed below and
the StatGraphics program.
Figure 2. Pilot Card
Figure 3. Wheelhouse poster
4 SIMULATION TESTS- NO. 3 ANCHORAGE,
EXTERNAL PORT IN ŚWINOUJŚCIE.
Parameters of No.3 anchorage of the external port in
Świnoujście were used in simulation scenario of the
behaviour of a model of LNG carrier at anchor.
In the simulation series, a 15.5 m lowest depth was
assumed in the entire area of the anchorage. The ship
lies at anchor, port anchor with the length of the
anchor cable of 7 shackles. The simulation begins
after the initial positioning of the model at anchor in
relation to the operating disturbances (wind,
undulations). A continuous time tape with a nominal
length of 03:00:00 [hh: mm: ss] was built, in which for
the given wave spectrum the wind speed and the
wave height are continuous non-decreasing functions.
In the simulation, the wind speed domain was
limited to the value of 6 m / s. The parameters of the
generated waves were determined and the results of
simulation tests were obtained for winds (without
squalls) of the speed of 6, 9, 12, 1 m / s and 15.1 - 18.0
m / s every 0.1 m / s. The moment of complete loss of
under keel clearance (hull contact with the bottom)
was assumed as the end of the simulation. An
example of a screenshot from electronic navigation
chart with positions (contour) of LNG ship model at
anchor is shown in Fig. 4.
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Figure 4. An example of a screenshot from electronic navigation
chart with the positions (contour) of LNG ship model at anchor.
The simulation, in particular, examined the course
of the variability of under keel clearance (UKC) with
the set disturbance parameters (hydro-meteorological
conditions). The wind speed/velocity (vw) and the
change of under keel clearance in the bow and stern
parts obtained from measurements based on sensors
located in the symmetry line of the bottom of the
LNG carrier model are presented in the attached
graphs below as a function of time.
In connection with the implementation of the task
consisting in determining the boundary conditions,
the attached drawings (Fig. 5-Fig. 13) present the
results of tests, covering the period of the last 5
minutes of the simulation. The positive value of
under-keel clearance, read each time, at the end of the
simulation, is related to the hull contact with the
bottom at the occurrence of the ship's rolling.
Simulations were also carried out, taking into account
additional influence of squalls (No.134, 134a, 136
simulations) and swell (No.129-133 and 136
simulations). The parameters of the simulations have
been presented in Tab. 1.
Figure 5 .Graph of UKC changes and V
w
(No. 109 simulation)
Figure 6. Graph of UKC changes and V
w
(No. 134a simulation)
Figure 7. Graph of UKC changes and V
w
(No. 129 simulation)
Figure 8. Graph of UKC changes and V
w
(No. 130 simulation)
Table 1. Simulation parameters of the model of LNG carrier at anchor.
__________________________________________________________________________________________________
No. of True wind Wind Swell Squalls Dragging Contact with the bottom
simulations direction Direction Hdg anchor Wind speed/velocity
[°] [°] [°] Vw [m/s]
__________________________________________________________________________________________________
109 000 000 - No No 16,6
134 000 000 - Yes Yes -
134a 000 000 - Yes No 17,5
136 000 000 045 Yes No 17,1
129 000 000 000 No No 16,8
130 000 000 045 No No 16,7
131 000 000 090 No No 16,9
132 000 000 135 No No 17,3
133 000 000 180 No No 16,6
__________________________________________________________________________________________________
947
Figure 9. Graph of UKC changes and Vw (No. 131
simulation)
Figure 10. Graph of UKC changes and Vw (No. 132
simulation)
Figure 11. Graph of UKC changes and Vw (No. 133
simulation)
Figure 12. Graph of UKC changes and Vw (No. 134
simulation)
Figure 13 Graph of UKC changes and Vw (No. 136
simulation)
The developed theoretical model examines the
under keel clearance of LNG ship at anchor and the
boundary conditions of the ship's contact with the
bottom. Based on the carried out simulation studies
and the need for high accuracy and precision of the
measurements of the UKC for LNG carrier, new
measurements of hydro-meteorological conditions
must be carried out in order to collect current and
accurate data, in particular the observed wave and
current parameters in the Pomeranian Bay area, with
particular emphasis on the expected trajectory of
LNG carriers calling at the port of Świnoujście
(including the approach channel and anchorages).
The observations of the maritime administration
services responsible for the measurements in the
Pomeranian Bay area indicate that the pressure
change itself associated with the transition of the
barometric systems induces a significant change in
the water level in the approach channel, which is
expressed in the differences in the depth reading. The
knowledge of at least an estimate of frequent changes
in depth caused by a change in specific hydro-
meteorological conditions is of significant importance
in determining the expected under keel clearance for
master of LNG vessel that is fully loaded and the
shore side services (Captain's Office, VTS, pilot
station) co-responsible for safe passage of the ship to
the LNG terminal in Świnoujście. Changes in the
water level significantly affect the actual depth. The
accuracy of the depth determination by hydrographic
institutions is strictly defined by relevant IMO
regulations, in particular, of a water depth of 10.0-
20.0 m, the measurement accuracy is 0.20 m.
The greatest hazard in shallow water, which has
been the cause of many contacts of a hull with seabed,
is the undulations and related movements of a ship,
which obviously reduce the distance between the hull
and the bottom. Table 2 shows examples of reduction
in under keel clearance for tankers of various
dimensions caused by undulations/ wind wave.
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Table 2. Reduction in UKC caused by the waves[1]
__________________________________________________________________________________________________
Ship’s Wave WAVE DIRECTION
particulars Hight Period 000° 090° 045° or 135°
[m] [s] Pitching Heave Sum Rolling Heave Sum Pitching Rolling Heave Sum Fwd Midship Fwd or
[m] [m] [m] [m] [m] [m] [m] [m] [m] or Aft [m] [m] Aft [m]
__________________________________________________________________________________________________
Deadweight 4,57 10 2,80 0,15 2,96 2,93 2,13 5,06 2,50 2,35 0,76 3,26 3,11 3,93
=17049 t 1,83 10 1,07 0,06 1,13 1,13 0,91 2,04 0,97 0,91 0,30 1,28 1,22 1,52
L= 149,00 m
B= 21,60 m
T= 9,14 m
Deadweight 4,57 10 2,80 0,30 3,11 3,78 1,52 5,30 2,50 3,05 0,53 3,05 3,58 4,42
=37594t 1,83 10 1,07 0,12 1,14 1,46 0,61 2,07 0,97 1,16 0,21 1,19 1,37 1,68
L= 203,00 m
B= 28,00 m
T= 10,97 m
Deadweight 4,57 10 2,74 0,24 2,99 4,02 1,07 5,09 2,47 3,20 0,37 2,83 3,57 4,39
=45722t 1,83 10 0,91 0,09 1,00 1,55 0,49 2,04 0,82 1,25 0,15 0,97 1,40 1,68
L= 216,00 m
B= 29,80 m
T= 11,58 m
Deadweight 4,57 10 2,47 0,15 2,62 4,45 0,82 5,27 2,22 3,57 0,29 2,53 3,87 4,60
=60963t 1,83 10 0,82 0,08 0,91 1,74 0,33 2,07 0,73 1,37 0,11 0,85 1,49 1,74
L= 236,00 m
B= 32,90 m
T= 12,44 m
Deadweight 4,57 10 2,20 0,12 2,38 4,88 0,61 5,49 1,98 3,90 0,21 2,19 4,11 4,75
=81284t 1,83 10 0,97 0,00 0,97 1,89 0,24 2,13 0,88 1,52 0,08 0,97 1,61 1,92
L= 257,00 m
B= 36,30 m
T= 14,02 m
__________________________________________________________________________________________________
Calculation of UKC at anchorage on the basis of
simulation tests was determined on the basis of the
following formulas:
( )
( ) ( )
( )
min ,
UKC symulator
Under Keel Clearance f wd m Under Keel Clearance aft m
=
( )
( )
Roll angle π
25
180
UKC UKC symulator sin
= −
.
where:
under keel clearance fwd(m) – UKC on the FWD [m],
under keel clearance aft(m) – UKC at AFT [m],
roll angle – rolling.
5 STATISTICAL ANALYSIS OF SIMULATION
RESULTS FOR A MODEL OF LNG CARRIER AT
ANCHOR.
The basic statistical parameters of the data obtained
from simulations for LNG carrier at anchor have been
presented in Tab. 3 and Fig. 14.
Table 3. Statistical parameters
_______________________________________________
Simulation Avarage Standard Coefficient Standard
deviation of variation error
_______________________________________________
109 3,27415 0,375892 11,4806% 0,00414447
129 3,14816 0,503874 16,0054% 0,00530718
130 3,15613 0,452964 14,3519% 0,00489842
131 2,95505 0,592045 20,035% 0,00618968
132 2,89295 0,579977 20,0479% 0,00574122
133 3,10199 0,455714 14,691% 0,0049907
134a 2,91225 0,677372 23,2594% 0,00603451
134 2,92489 0,66794 22,8364% 0,00592026
136 2,94684 0,717248 24,3396% 0,00754747
Sum 3,0197 0,59489 19,7003% 0,00200716
_______________________________________________
Figrue 14. Box plot for UKC for a model of LNG tanker at
anchor
For the data obtained from the simulation, the
Kruskal-Wallisai test was performed. The rank test
for mean medians is shown in Table 4, Table 5 and
Table 6.
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Table 4. Kruskal-Wallis test.
_______________________________________________
Simulation Sample Size Average Rank
_______________________________________________
109 8226 57605,1
129 9014 49593,0
130 8551 48131,0
131 9149 39556,2
132 10205 36338,5
133 8338 44090,2
134a 12600 41192,8
134U 12729 41913,6
136 9031 41288,4
_______________________________________________
Test statistic = 4588,9 P-Value = 0,0
Method: 95,0 percent LSD
Table 5. Multiple rank test,
_______________________________________________
Simulation Count Mean Homogeneous Groups
_______________________________________________
132 10205 2,89295 X
134a 12600 2,91225 X
134 12729 2,92489 X
136 9031 2,94684 X
131 9149 2,95505 X
133 8338 3,10199 X
129 9014 3,14816 X
130 8551 3,15613 X
109 8226 3,27415 X
_______________________________________________
Both the rank test for mean and the Kruskal-Wallis
test for medians indicate a statistically significant
differentiation of the samples, i.e. the influence of the
wind direction and swell on under keel clearance.
Tab. 7 and Tab. 8. show classes of under keel
clearance obtained from the simulation.
Probability of UKC not exceeding 1.2 m (10%
reserve), 1.8 m (15% reserve) and 2.4 m (20% reserve)
thresholds and not exceeding the 2.4 m threshold for
a draft of 12 m and individual test variants are
presented in Table 9.
Table 6. Test for simulation pairs
_______________________________________________
pairs Sig. difference +/- limits
_______________________________________________
109 – 129 * 0,12599 0,0173725
109 – 130 * 0,118016 0,0175955
109 – 131 * 0,319097 0,0173113
109 – 132 * 0,381193 0,0168819
109 – 133 * 0,172152 0,0177054
109 – 134a * 0,361896 0,01615
109 – 134 * 0,349255 0,0161176
109 – 136 * 0,327309 0,0173647
129 – 130 -0,0079734 0,0171991
129 – 131 * 0,193107 0,0169082
129 – 132 * 0,255203 0,0164683
129 – 133 * 0,0461625 0,0173114
129 - 134a * 0,235907 0,0157171
129 – 134 * 0,223265 0,0156838
129 – 136 * 0,20132 0,0169629
130 – 131 * 0,20108 0,0171372
130 – 132 * 0,263176 0,0167033
130 – 133 * 0,0541359 0,0175352
130 - 134a * 0,24388 0,0159632
130 – 134 * 0,231239 0,0159305
130 – 136 * 0,209293 0,0171912
131 – 132 * 0,0620961 0,0164036
131 – 133 * -0,146944 0,01725
131 – 134 * 0,0427997 0,0156493
131 – 134 * 0,0301584 0,0156159
131 – 136 0,0082126 0,0169001
132 – 133 * -0,209041 0,016819
132 – 134a * -0,0192964 0,015173
132 – 134 * -0,0319377 0,0151385
132 – 136 * -0,0538835 0,01646
133 - 134a * 0,189744 0,0160842
133 – 134 * 0,177103 0,0160517
133 – 136 * 0,155157 0,0173036
134a – 134 -0,0126413 0,0143177
134a – 136 * -0,0345871 0,0157084
134 - 136 * -0,0219458 0,0156752
_______________________________________________
* means a statistically significant difference
The analysis of the impact of wind speed on UKC
variable is presented in Table 10 and in Fig. 15
Table 7. Classification into classes for UKC.
__________________________________________________________________________________________________
T 109 129 130 131 132
Range Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative
[m] frequent relative frequent relative frequent relative frequent relative frequent relative
frequent frequent frequent frequent frequent
__________________________________________________________________________________________________
(0;0,6] 0,38% 0,38% 0,62% 0,62% 0,51% 0,51% 0,70% 0,70% 0,24% 0,24%
(0,6;1,2] 0,26% 0,63% 0,59% 1,21% 0,49% 1,01% 0,86% 1,56% 0,82% 1,07%
(1,2;1,8] 0,90% 1,53% 2,25% 3,46% 1,34% 2,35% 3,08% 4,65% 4,51% 5,58%
(1,8;2,4] 1,60% 3,14% 4,27% 7,73% 2,60% 4,95% 9,12% 13,76% 12,30% 17,87%
(2,4;3] 4,25% 7,39% 9,29% 17,02% 13,25% 18,20% 27,82% 41,58% 32,37% 50,24%
(3;3,6] 92,57% 99,96% 82,85% 99,87% 81,25% 99,45% 55,77% 97,34% 46,14% 96,38%
≥3,6 0,04% 100,00% 0,13% 100,00% 0,55% 100,00% 2,66% 100,00% 3,62% 100,00%
__________________________________________________________________________________________________
Table 8. Classification into classes for UKC.
__________________________________________________________________________________________________
T 133 134a 134 136
Range Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative
[m] frequent relative frequent relative frequent relative frequent relative
frequent frequent frequent frequent
__________________________________________________________________________________________________
(0;0,6] 0,62% 0,62% 0,52% 0,52% 0,43% 0,43% 1,72% 1,72%
(0,6;1,2] 0,19% 0,82% 2,42% 2,94% 2,26% 2,69% 2,10% 3,82%
(1,2;1,8] 0,65% 1,46% 6,37% 9,31% 6,06% 8,75% 4,55% 8,37%
(1,8;2,4] 3,63% 5,10% 10,87% 20,17% 11,53% 20,28% 6,44% 14,82%
(2,4;3] 23,81% 28,90% 16,28% 36,45% 15,40% 35,68% 15,48% 30,30%
(3;3,6] 69,61% 98,51% 63,29% 99,75% 64,21% 99,89% 68,84% 99,14%
≥3,6 1,49% 100,00% 0,25% 100,00% 0,11% 100,00% 0,86% 100,00%
__________________________________________________________________________________________________
950
Table 9. Probability of occurrence of under keel clearance (UKC)
__________________________________________________________________________________________________
Probability 109 129 130 131 132 133 134a 134 136
__________________________________________________________________________________________________
UKC≤1,2 0,63% 1,21% 1,01% 1,56% 1,07% 0,82% 2,94% 2,69% 3,82%
UKC≤1,8 1,53% 3,46% 2,35% 4,65% 5,58% 1,46% 9,31% 8,75% 8,37%
UKC≤2,4 3,14% 7,73% 4,95% 13,76% 17,87% 5,10% 20,17% 20,28% 14,82%
UKC>2,4 96,86% 92,27% 95,05% 86,24% 82,13% 94,90% 79,83% 79,72% 85,18%
__________________________________________________________________________________________________
Table 10. Statistical Parameters
__________________________________________________________________________________________________
Wind speed UKC avarage Standard deviation Coefficient of variation Qantile quarter Quantile six
__________________________________________________________________________________________________
up to 10 m/s 3,28688 0,417243 12,6942% 3,30235 3,14154
up to 12 m/s 3,28151 0,421774 12,853% 3,29012 3,12717
up to 14 m/s 3,29642 0,383915 11,6464% 3,30065 3,15747
up to 16 m/s 3,2585 0,312357 9,58591% 3,16783 3,0837
up to 18 m/s 3,06272 0,579803 18,931% 2,99711 2,72243
up to 20 m/s 3,06384 0,579493 18,9139% 2,9987 2,72492
up to 20 m/s 2,80615 0,73121 26,0574% 2,5247 2,16831
10-12 m/s 3,02875 0,540676 17,8514% 2,89459 2,56924
12-14m/s 3,33355 0,263622 7,90815% 3,31599 3,21929
14-16m/s 3,22122 0,213972 6,64257% 3,12269 3,06042
16-18m/s 2,61657 0,770409 29,4435% 2,14196 1,84353
18-20m/s 3,24475 0,495649 15,2754% 3,2171 3,10972
__________________________________________________________________________________________________
Table 11. Probabilities for UKC variable for different wind speed.
__________________________________________________________________________________________________
Vw up to 10m/s up to 12m/s up to 14m/s up to 16m/s up to 18m/s up to 20m/s
UKC_10 UKC_12 UKC_14 UKC_16 UKC_18 UKC_20
Range Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative RelativeCumulative
UKC [m] frequent relative frequent relative frequent relative frequent relative frequent relative frequent relative
frequent frequent frequent frequent frequent frequent
__________________________________________________________________________________________________
[0; 0,1] 0,00% 0,00% 0,00% 0,00% 0,01% 0,01% 0,01% 0,01% 0,31% 0,31% 0,31% 0,31%
[0,1;0,3] 0,01% 0,01% 0,01% 0,01% 0,01% 0,02% 0,00% 0,01% 0,05% 0,36% 0,05% 0,36%
[0,3;0,5] 0,02% 0,03% 0,03% 0,04% 0,02% 0,04% 0,01% 0,02% 0,12% 0,48% 0,13% 0,49%
[0,5;0,7] 0,06% 0,10% 0,06% 0,10% 0,05% 0,09% 0,02% 0,05% 0,16% 0,64% 0,16% 0,65%
[0,7;0,9] 0,16% 0,26% 0,16% 0,26% 0,13% 0,21% 0,07% 0,12% 0,35% 1,00% 0,35% 1,00%
[0,9;1,1] 0,23% 0,49% 0,25% 0,51% 0,19% 0,40% 0,10% 0,21% 0,54% 1,53% 0,53% 1,53%
[1,1;1,3] 0,36% 0,85% 0,35% 0,86% 0,27% 0,67% 0,15% 0,36% 0,76% 2,29% 0,76% 2,29%
[1,3;1,5] 0,43% 1,28% 0,44% 1,30% 0,32% 0,99% 0,17% 0,53% 1,01% 3,30% 1,00% 3,29%
[1,5;1,7] 0,55% 1,83% 0,58% 1,88% 0,43% 1,41% 0,22% 0,75% 1,27% 4,58% 1,27% 4,56%
[1,7;1,9] 0,71% 2,55% 0,74% 2,61% 0,57% 1,98% 0,32% 1,07% 1,70% 6,27% 1,69% 6,26%
[1,9;2,1] 0,78% 3,33% 0,82% 3,43% 0,65% 2,63% 0,39% 1,45% 1,98% 8,26% 1,98% 8,23%
[2,1;2,3] 0,83% 4,16% 0,88% 4,31% 0,72% 3,35% 0,47% 1,92% 2,19% 10,45% 2,18% 10,41%
[2,3;2,5] 1,66% 5,82% 1,70% 6,01% 1,52% 4,88% 0,97% 2,89% 2,66% 13,11% 2,65% 13,07%
[2,5;2,7] 2,32% 8,14% 2,39% 8,40% 2,01% 6,89% 1,57% 4,46% 3,10% 16,21% 3,10% 16,16%
[2,7;2,9] 2,75% 10,89% 2,79% 11,19% 2,91% 9,80% 3,36% 7,82% 4,82% 21,03% 4,81% 20,97%
[2,9;3,1] 4,28% 15,17% 4,48% 15,67% 4,54% 14,34% 10,13% 17,95% 10,79% 31,83% 10,76% 31,73%
[3,1;3,3] 9,72% 24,88% 9,98% 25,65% 10,62% 24,96% 25,79% 43,74% 24,17% 56,00% 24,11% 55,84%
(3,3;3,5] 70,78% 95,66% 70,04% 95,69% 70,70% 95,66% 52,10% 95,84% 40,49% 96,48% 40,65% 96,49%
(3,5;3,7] 4,33% 99,99% 4,30% 99,99% 4,30% 99,96% 4,08% 99,92% 3,43% 99,92% 3,43% 99,92%
(3,7;3,9] 0,01% 100,00% 0,01% 100,00% 0,04% 100,00% 0,08% 100,00% 0,08% 100,00% 0,08% 100,00%
__________________________________________________________________________________________________
Table 12. Probabilities for UKC variable for different wind speed.
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Vw from 20m/s 10m/s - 12m/s 12m/s - 14m/s 14m/s - 16m/s 16m/s - 18m/s 18m/s - 20m/s
UKC_from 20 UKC10_12 UKC12_14 UKC14_16 UKC16_18 UKC18_20
Range Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative Relative Cumulative RelativeCumulative
UKC [m] frequent relative frequent relative frequent relative frequent relative frequent relative frequent relative
frequent frequent frequent frequent frequent frequent
__________________________________________________________________________________________________
[0; 0,1] 1,44% 1,44% 0,00% 0,00% 0,03% 0,03% 0,01% 0,01% 0,99% 0,99% 0,53% 0,53%
(0,1;0,3] 0,07% 1,52% 0,00% 0,00% 0,00% 0,03% 0,00% 0,01% 0,16% 1,15% 0,00% 0,53%
(0,3;0,5] 0,17% 1,69% 0,32% 0,32% 0,00% 0,03% 0,00% 0,01% 0,38% 1,53% 0,53% 1,06%
(0,5;0,7] 0,30% 1,99% 0,00% 0,32% 0,02% 0,05% 0,00% 0,01% 0,48% 2,01% 0,00% 1,06%
(0,7;0,9] 0,65% 2,64% 0,00% 0,32% 0,05% 0,10% 0,01% 0,02% 1,00% 3,00% 0,00% 1,06%
(0,9;1,1] 0,67% 3,31% 0,96% 1,28% 0,03% 0,13% 0,01% 0,03% 1,54% 4,55% 0,00% 1,06%
(1,1;1,3] 1,19% 4,50% 0,00% 1,28% 0,07% 0,20% 0,03% 0,06% 2,16% 6,70% 0,00% 1,06%
(1,3;1,5] 1,49% 5,99% 0,64% 1,92% 0,02% 0,22% 0,02% 0,07% 2,92% 9,63% 0,53% 1,58%
(1,5;1,7] 1,89% 7,88% 1,92% 3,83% 0,05% 0,27% 0,02% 0,10% 3,66% 13,29% 1,06% 2,64%
(1,7;1,9] 3,31% 11,19% 1,92% 5,75% 0,15% 0,41% 0,07% 0,16% 4,85% 18,14% 0,79% 3,43%
(1,9;2,1] 3,85% 15,05% 2,56% 8,31% 0,22% 0,63% 0,14% 0,30% 5,62% 23,76% 0,53% 3,96%
(2,1;2,3] 3,90% 18,95% 3,19% 11,50% 0,33% 0,96% 0,22% 0,52% 6,11% 29,87% 1,06% 5,01%
(2,3;2,5] 5,32% 24,27% 3,51% 15,02% 1,09% 2,06% 0,42% 0,94% 6,53% 36,40% 1,06% 6,07%
(2,5;2,7] 5,22% 29,50% 5,43% 20,45% 1,08% 3,13% 1,13% 2,07% 6,60% 43,00% 2,11% 8,18%
(2,7;2,9] 7,63% 37,13% 5,11% 25,56% 3,22% 6,35% 3,79% 5,86% 8,15% 51,15% 2,64% 10,82%
(2,9;3,1] 15,24% 52,38% 13,74% 39,30% 4,69% 11,04% 15,64% 21,50% 12,30% 63,44% 5,28% 16,09%
951
(3,1;3,3] 25,02% 77,39% 2 2,36% 61,66% 12,21% 23,25% 40,70% 62,19% 20,50% 83,94% 13,46% 29,55%
(3,3;3,5] 20,69% 98,09% 35,46% 97,12% 72,34% 95,59% 33,82% 96,01% 14,01% 97,96% 67,28% 96,83%
(3,5;3,7] 1,91% 100,00% 2,88% 100,00% 4,29% 99,88% 3,86% 99,88% 1,96% 99,92% 2,90% 99,74%
(3,7;3,9] 0,00% 0,00% 0,12% 100,00% 0,12% 100,00% 0,08% 99,99% 0,00% 99,74%
(3,9;4,1] 0,01% 100,00% 0,26% 100,00%
__________________________________________________________________________________________________
Figure 15. Box plot for UKC for a model of LNG vessel at
anchor with different wind speed limits.
The simulation conclusions are included in Tab. 11
and Table 12, which contain the event probabilities
that UKC variable [m] takes values from a given
range for different wind speed ranges.
6 CONCLUSIONS
Designating safe anchorages for LNG carriers is one
of the main tasks for safe operation of a terminal
handling liquid fuels, especially LNG.
Important issue is the influence of hydro-
meteorological conditions in determining the
anchorage areas for LNG carriers.
The aim of the simulations was to indicate the
conditions that should be taken into account when
determining the anchorage, so that under keel
clearance was proper during the entire period of the
ship's stay at anchor in various weather conditions.
The simulations and analysis (Tab. 2.1 and Tab.
2.2) have shown that the probability of a change in
under keel clearance to the limit values ranging from
0.0 m to 0.1 m may occur with a probability frequency
of 0.01% at wind speed 16 m / s (31kts).
The increase in wind speed above 16 m / s (31 kts)
results in the increase in frequency of UKC
occurrence by 0.0m to 0.1m with a probability of
0.99%. On the basis of the above values, it can be
assumed that the UKC for No. 3 anchorage area, has
safe values (for this type of LNG carrier) up to wind
speed of 16 m / s (31 kts). The ship model was at
anchor/brought up all the time of simulation.
Dragging of the anchor only occurred in the event of
disturbances caused by squall. Simulation tests and
their analysis have indicated that a vessel can lie at
anchor at No. 3 anchorage safely with wind speed up
to 16m / s (31 kts). With expected wind speed above
16 m / s (31 knots), recommendation for the vessel is
to heave up anchor and move for deeper open water.
The used methodology of simulation tests can be
used to determine the conditions of safe anchoring
for this type and size of ships taking into account
their under keel clearance in various weather
conditions.
REFERENCES
1. Załącznik graficzny nr 1 do wniosku o wydanie
pozwolenia na wznoszenie konstrukcji w polskich
obszarach morskich. / Graphic appendix No. 1 to the
application for a permit to erect structures in Polish sea
areas
2. Pozwolenie Ministra Infrastruktury nr 48/08 z dnia 19
czerwca 2011 r./ Permit of the Minister of
Infrastructure No. 48/08 of June 19, 2011.
3. Pismo Dyrektora Urzędu Morskiego Znak: TI-
220/9/1383/2011 z dnia 06.06.2011 r./ Letter of the
Director of the Maritime Office Ref: TI-220/9/1383/2011
from 06.06.2011.
4. Wyniki badań falowania w porcie zewnętrznym w
Świnoujściu (optymalny wariant lokalizacji) wykonane
przez BMT Cordahsp.z o.o. w Gdańsku / The results of
wave tests in the external port in Świnoujście (optimal
location variant) made by BMT Cordahsp. in Gdansk
5. Proj. Nr OW-22/12-2/2005 „WUPROHYD” Gdynia
6. G. Rutkowski, „Ocena głębokości północnego toru
podejściowego do portu Świnoujście od pozycji gazo
portu NordStream do terminalu LNG w aspekcie
obsługi jednostek o maksymalnych gabarytach”.
