845
1 INTRODUCTION
Moored vessels at port terminals may be subject to
excessive strain on mooring ropes, induced by
passage of other vessels in their vicinity. This
phenomenon is called hydrodynamic interaction and
is well known in the international literature as passing
ship. It occurs due to the displacement of the water
mass between the two vessels, which induces
hydrodynamic stresses on both vessels (moving vessel
and berthed vessel). The moored vessel may be
subject to excessive displacement, and consequently
overloading the mooring lines and fenders, which
may result, in extreme circumstances, in breaking
cables and damage to the fender system. In addition,
according to the progress of the cargo handling
operation, there may be damage to the ship.
The passing ship is particularly important to ports
located at confined areas or in narrow channels,
where the phenomena can be magnified, representing
an important issue for the safety assessment of port
operations.
In such situations, ASCE [1] recommends the
analysis of the passing ship phenomena through scale
or numerical modeling.
Numerical modeling utilizes simplified equations
[3] and graphs based on the parameters: the berth
depth, the distance between moored and passing
ships, the passing ship speed, and coefficients that are
related to vessel geometry. These equations estimate
longitudinal and transversal forces, and the moment
of force on the moored vessel generated by a ship
passage, based on the distance between the ships and
the relative size of the vessel. Therefore, this data
provides information of force and moment according
to the vessel position and geometry. The resultant
force and moment are used as input data to calculate
the force equilibrium at the mooring lines, to estimate
the load on each line.
Simulation in Reduced Scale Hydraulic Models of the
Mooring System of Ships Docked Under the Effect of
the Passage of Other Vessels (Passing Ship)
R. Esferra
1
, J.C. de Melo Bernardino
2
, R. de Oliveira Bezerra
1
& L.M. Pion
1
1
Hydraulic Technological Center Foundation, Sao Paulo, Brazil
2
University of Sao Paulo, Sao Paulo, Brazil
ABSTRACT: Vessels moored at port terminals may be subject to excessive strain on mooring lines, induced by
other ships passing in their vicinity. This phenomenon is called hydrodynamic interaction, and well known in
the international literature as Passing Ship. It occurs due to the displacement of the mass of water between the
two vessels, which, consequently, induces hydrodynamic stresses on the two ships. Within this context, scale
models are a powerful tool for hydrodynamics studies, being able of reproduce the complex water flow
phenomena that take place around passing and moored ship. This paper presents a scale model technique to
study the Passing Ship phenomenon and its application on a case study developed for the Santos Port. The
study was based on the analysis of the results of simulations performed on a 1:170 scale model to compare the
effect of various navigations conditions on the mooring lines of a docked ship.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 15
Number 4
December 2021
DOI: 10.12716/1001.15.04.17
846
However, this numerical modeling technique does
not consider the effect of important aspects
concerning passing ship phenomena, such as: (1)
channels physical characteristics (lateral slopes or
bathymetric variations); (2) geometry, type and
arrangement of mooring structures; (3) vessel`s hull
geometry; and (4) second order effects caused by
water displacement between the two vessels.
Furthermore, it is only possible to apply this method
when it is possible to consider ships navigating in
parallel with the moored ship as an assumption.
Despite the limitations, the numerical approach can be
applied on low complexity situations or as an initial
approximation for the problem.
The three-dimensional scale models, which are a
small-scale reproduction of the problem are a
powerful tool for hydrodynamic studies. When
correctly built and calibrated, the scale models can
emulate satisfactorily all the forces involved in the
passing ship phenomena. The bathymetry,
hydrodynamic processes, vessels hull (moored and in
motion), the propulsion system, mooring lines, and
port structures are all reliably reproduced in the
model with respect to the real-life conditions. The
calibration procedure covers all features separately to
ensure a correct reproduction of the study area
conditions.
The hydrodynamic conditions reproduction is
guaranteed by the calibration of the current speed
(kinematic) and direction and water level and currents
direction. The mooring system representation
demands the calibration of the elastic characteristics of
the mooring lines and fenders. Finally, the mass and
inertia of small-scale vessels are also calibrated, and
simulations of the sea trial are performed to adjust
sailing and maneuvering behaviors (CrashStop, Zig-
Zag and Turning Circle maneuvers).
Therefore, this article presents the analysis of the
Passing Ship phenomenon at the warehouse 39 berth
in the Port of Santos (São Paulo, Brazil), based on
simulations performed on a hydrodynamic physical
model.
The Port of Santos is the main Brazilian port in
cargo transport, being responsible for more than 50%
of Brazil’s gross domestic product (GDP) since that
25% of the country exports and imports pass through
this port. The port is located at Santos Estuary, which
is approximately 20 kilometers long, 400 meters wide
and 14 meters deep. There are 16 kilometers of quays
and more than 60 mooring berths. The Estuary of
Santos is sheltered from the waves action and
maximum tide currents are about 1,0 m/s. These
hydrodynamics conditions are proper for port
operations.
As it is the main Brazilian port, the Port of Santos
has a high inflow and outflow of vessels, with an
average of 12,000 maneuvers per year and 33 per day.
Due to the restricted maneuvering area available and
the increase of vessels dimensions, the maneuvers
tend to be complex and riskier, and must be
performed increasingly closer to the nearest berthing
areas.
Therefore, motivated by the increase in the
dimensions of the ships operating in the Port of
Santos, and the complexity of Passing Ship
phenomenon, a study was carried at a scale model to
evaluate the mooring system performance for a vessel
with 125.000 DWT, docked at warehouse 39 during
the passage of a ship with LOA = 366 m (L366m).
The objective of this article is to present the
analysis method for the Passing Ship phenomenon
utilizing scale modeling, presenting the technique for
carrying out the tests and the results from the case
study.
2 MATERIAL AND METHODS
According to ASCE [2], the passage of a vessel near to
a moored ship disturbs the body of water between the
two vessels, forcing the moored one to move in a
characteristic pattern:
1 1. The moored ship is shifted to the same direction
of the passing ship;
2 2. The moored vessel moves in opposite direction
of the sailing ship;
3 3. The moored ship translates away from the berth;
4 4. The docked ship moves to the same direction of
passing ship one more time;
5 5. The moored ship dislocates to the opposite
direction of the passing ship again;
6 6. The moored ship returns close to its initial
position, reestablishing the load balance at the
mooring lines.
The main variables involved in this phenomenon
are: the geometry of the vessels hull, the speed of the
passing ship, the position and location of the sailing
vessel, the channel and berth region geometry, the
moored ship orientation, and dynamic properties of
the mooring system.
Due to the high complexity of this phenomenon,
this study was performed using a scale model of the
Santos Estuary, built on an undistorted scale of 1:170.
The model occupies approximately 2,280 m² at the
CTH-USP (Technological Hydraulics Center of São
Paulo University) and reproduces the region of the
Santos Estuary (Figure 1).
Figure 1. Nautical Chart Nº 1711 form the Hydrographic
and Navigation Board from the Brazilian Navy, with the
scale model area highlighted.
The bathymetry of the model was reproduced
accordingly with HS (Hydrographic Surveys)
provided by CODESP and the nautical chart number
1711, edited by the Hydrographic and Navigation
Board (DHN) from the Brazilian Navy. The only
environmental condition reproduced are tide
currents, since, as previously described, the inner
847
portion of the Santos Estuary is sheltered from waves
and the wind stress does not exert great influence on
the vessels.
Therefore, after a careful environmental data
analysis, the spring tide condition was chosen to be
simulated during the tests, with amplitudes of 1.83 m
for the ebb tide and 1.70 m for the flow tide, both with
a speed of approximately 1m/s. The georeferenced
environmental data used in the calibration process
were extracted from a numerical model developed by
the CTH for the Santos Estuary region.
In addition to the boundary conditions, the
geometry of the vessel models hull is reproduced
accordingly with the Line Plan (ship’s structural
project with its curvature) of the real ships (Figure 2
and Figure 3) respecting the adopted geometric
similarity constraints. Furthermore, the nature of
Passing Ship phenomenon imposes the necessity to
calibrate the mass and inertia characteristics of both
vessel models, and the sailing model are submitted to
sea trial simulations to calibrate its maneuverability
and propellant system. To further details, see [2].
Figure 2. Real project of the Line Plan of the 366 m long
vessel.
Figure 3. Scale model of the 366 m long vessel.
To control the ship the maneuvers were executed
with the Analogical Maneuvering System (SIAMA).
The system is an analog simulation tool for ships
unmanned maneuvers in three-dimensional scale
models that can be applied to any waterway scale
model that has sufficient scale reduction and
reproduction area to perform maneuver tests. The
system is controlled by software developed by CTH-
USP, which, during the maneuvers, is capable to
control and monitor the conditions of engine power,
rudder angle and, if necessary, actuation of the tugs,
among other information of interest. This tool also has
a ship tracking system, known as ship tracking, which
works through images generated by a set of digital
cameras installed in zenith and distributed along the
model, to cover the entire actuation area of the vessel
during the maneuvering tests (Figure 4).
Figure 4. Sample ship trajectory registered by the ship
tracking system utilized in the scale model.
The mooring plans of the ships, which are the
projects that present the position of the cables and
their characteristics, were elaborated considering
cables working as sterns, heads, breasts and springs
(as schematically represented in Figure 5). In scale
models, it is often not possible to represent all cables
individually due to the reduction scale. When this
occurs, cables composed by same material and
performing the same function (such as forward
breasts, after springs, etc.) are represented in the tests
by a single line, without compromising the individual
analysis of each real cable, since stress can be easily
decomposed between them later.
Figure 5. Simplified sketch of the main line types utilized in
the mooring plans of vessels docked at portuary terminals.
As well as the physical modeling of the mooring
system is obtained through rope assemblies connected
to coiled springs. The springs are calibrated on a
specific bench to reproduce the real rope linear
modulus of elasticity in a reduced scale, respecting
the curves of strength x deformation for each rope to
be represented. The sensors that measure the spring
displacements in the physical model are called LVDT
(Linear Variable Differential Transformer), and the
obtained values are recorded every second in a
computational database for subsequent strength
pattern analysis in the lines throughout the whole test.
The positions and elevations of the mooring
devices on the vessel and on the pier are precisely
respected, ensuring the correct representation of the
angles between the lines and pier and the lines and
848
the vessel observed in the Terminal. Prior to the start
of the test itself, with the vessel fixed at the berthing
line and centered on the berth, the lines are
strenghtened to 10% of the MBL (Minimum Breaking
Load, which is the reference of the minimum nominal
breaking load of one rope), like what happens in the
mooring of an actual vessel.
As mooring plan evaluation criteria were
considerate two limiting factors: the mooring lines
load, which should not be higher than 55% of the lines
MBL [6], and the vessel motions, which should not
exceed the maximum horizontal limit for belt loaders
presented in PIANC [6]:
1 1. Surge – 5,0 m (peak to peak)
2 2. Sway – 2,5 m (from the berthing line)
3 3. Yaw – 3,0° (peak to peak)
Thus, the tests simulated were with the passage of
a ship with a LOA = 366 m (L366), fully loaded (14m),
sailing with 8 knots in three pre-defined trajectories:
right margin (RM), center of the channel (C) and left
margin (LM). The tests simulated the ship entering
and exiting the port area (Figure 6)
Figure 6. Passing ship trajectories tested in scale model.
The 125,000 DWT ship was docked with a mooring
plan (ARM39) based on the standard mooring utilized
at Port of Santos, informed by CODESP (Figure 7).
The plan is composed of 12 lines of Polyblend 8 legs,
with 72 mm diameter and 84 tf MBL (Minimum
Breaking Load), arranged symmetrically, from stern
to bow, being: 2 Sterns (St), 2 After Breasts (AB), 2
After Springs (AS), 2 Forward Springs (FS), 2 Forward
Breasts (FB), and 2 Heads (Hd).
Figure 7. Mooring Plan “Arm 39”.
Considering that, the maneuver of the passing ship
is carried out in a freeway, being controlled only by
its propulsion system (propeller and rudder), some
degree of variations in its trajectory is expected,
similarly to the actual maneuver. Therefore, for each
scenario, several replications were performed to
consolidate the results. However, the results of only
three trials will be exposed, selected by presenting one
of the following criterions: the smaller deviations
presented in Ship Tracking and the exact 8 knots of
the passing ship during the course in each trajectory.
3 RESULTS AND DISCUSSION
The following results were extracted from the
Technical Report number 5, from the Hydraulics
Laboratory from USP’s Escola Politécnica [4]. The
results will be presented for the four sceneries
combinations of the passing L366 ship (entrance/exit –
ebb/flow tide). The data is divided into three tables,
one for each trajectory, exposing the mooring line
load values and the moored ship motions.
The tables present the maximum, mean and
standard deviations values of the mooring lines loads,
and the measured motions of the moored ship for
each test repetition. When the values exceed the
recommended limits, they are marked in red.
Due to the low variability of obtained results, the
graphs with temporal series of the moored ship
movements and its mooring lines loads will be
presented in attachment, as well the trajectories of the
container ship L366.
3.1 Scenario 1– Passing ship entering the port in the flow
tide
Table 1. (SC1) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Right margin
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
RM1 L máx 52 29 48 29 46 28
6,2 3,6 1,6
RM3 L máx 50 25 43 23 43 32
4,9 3,3 1,8
RM8 L máx 55 27 46 24 46 35
5,4 3,6 1,5
52 27 45 26 45 32 5,5
3,5
1,6
55 29 48 29 46 35 6,2
3,6
1,8
3 2 3 3 2 4 0,7
0,2
0,1
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
Table 2. (SC1) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Channel center
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
CC4 L máx 16 12 16 14 16 12
2,4 1,1 0,6
CC5 L máx 20 13 22 15 23 16
2,9 1,5 0,7
CC7 L máx 20 13 23 14 23 17
2,9 1,4 0,5
19 13 20 14 21 15 2,7
1,3
0,6
20 13 23 15 23 17 2,9
1,5
0,7
3 0 4 1 4 3 0,3
0,2
0,1
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
849
Table 3. (SC1) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Left margin
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
LM2 L máx 5 3 6 7 8 9
0,8 0,3 0,5
LM5 L máx 6 6 5 10 8 9
0,9 0,5 0,5
LM6 L máx 6 5 7 8 10 10
1,0 0,6 0,6
5 5 6 8 9 9 0,9
0,4
0,5
6 6 7 10 10 10 1,0
0,6
0,6
1 1 1 1 1 1 0,1
0,1
0,0
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
In this scenario, the obtained results shows that the
mooring line loads and the moored ship
displacements exceeds the established limits only in
the tests were the passing ship navigated by the right
margin trajectory, the closer trajectory to the
warehouse 39. The most tensioned lines were the
Stern (St), After Spring (AS), and Forward Breast (FB).
For the L366 trajectories by the channel center and
the left margin, the evaluated criteria did not exceed
the adopted limits. Furthermore, is possible to observe
that results are coherent, as it possible to observe the
expected reduction in the mooring lines loads values
and measured motions of the moored ship as the
distance between the two ships increased. In addition,
the lines of the moored ship behaved similarly in the
tests of different trajectories, with the same lines being
the most tensioned in all trials, just differing in the
magnitude of the values obtained.
The graph of Figure 8 compares the mooring lines
loads obtained in the three tested trajectories,
illustrating the previous observations.
Figure 8. Mean maximum mooring line loads for all the
tested trajectories.
3.2 Scenario 2– Passing ship entering the port in the ebb
tide
Table 4. (SC2) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Right margin
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
RM2 L máx 85 39 53 36 53 44
6,6 5,2 2,2
RM6 L máx 79 47 56 36 56 38
7,6 4,8 2,7
RM9 L máx 84 50 51 39 55 47
6,6 5,1 3,2
83 46 53 37 55 43 6,9
5,1
2,7
85 50 56 39 56 47 7,6
5,2
3,2
3 6 3 2 1 5 0,6
0,2
0,5
Right Margin - Scenario 2
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
Table 5. (SC2) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Channel center
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
CC1 L máx 35 25 29 23 31 27
3,8 2,6 1,4
CC2 L máx 34 28 25 24 26 24
3,5 2,4 1,5
CC4 L máx 33 27 27 24 27 24
4,0 2,4 1,3
34 27 27 24 28 25 3,7
2,4
1,4
35 28 29 24 31 27 4,0
2,6
1,5
1 1 2 0 3 2 0,3
0,1
0,1
Channel Center - Scenario 2
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
Table 6. (SC2) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Left margin
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
LM2 L máx 20 15 18 18 19 18
2,6 1,6 1,0
LM6 L máx 25 17 17 18 19 17
2,8 1,6 1,0
LM7 L máx 23 17 21 17 22 17
2,8 1,6 0,8
23 16 19 18 20 17 2,8
1,6
1,0
25 17 21 18 22 18 2,8
1,6
1,0
2 1 2 1 2 0 0,1
0,0
0,1
Left Margin - Scenario 2
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
For the passing ship (L366) entering the port in the
ebb tide, practically all the mooring lines (except the
Forward Spring – FS) of the bulk carrier docked at the
warehouse 39 presented tension values that exceeded
the established limits during the tests of the right
margin trajectory. The ship’s motions also exceeded
the imposed limits in this condition.
For the tests where the ship sailed through the
center of the channel, the mooring lines loads
decreased noticeably, not exceeding the limits
adopted. However, the moored ship displacements
still exceeded the PIANC [6] recommendations.
The results obtained in the tests with the passing
ship sailing in the farther trajectory does not
presented any mooring line load or ship motion value
above the established limits.
Similarly, to the previous condition, the results of
this scenario tests showed consistency, with the
reduction of mooring lines loads as the passing ship
navigated through trajectories farther from the
mooring berth. The same loading distribution pattern
was observed in the mooring lines in all trajectory
conditions, as illustrated in Figure 9.
850
Figure 9. Mean maximum mooring line loads for all the
tested trajectories.
3.3 Scenario 3– Passing ship exiting the port in the flow
tide
Table 7. (SC3) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Right margin
trajectory
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
RM1 L máx 26 75 20 61 22 40
6,1 4,9 4,2
RM2 L máx 32 76 22 64 25 42
7,2 4,9 4,3
RM4 L máx 23 73 26 62 29 40
7,0 4,7 4,3
27 75 23 63 25 41 6,7
4,8
4,3
32 76 26 64 29 42 7,2
4,9
4,3
4 1 3 2 4 1 0,6
0,1
0,0
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
Table 8. (SC3) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Channel center
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
CC1 L máx 9 26 9 26 10 15
2,8 1,9 1,9
CC3 L máx 10 25 6 26 8 16
2,5 2,0 1,9
CC4 L máx 12 30 9 33 12 19
3,4 2,4 2,4
10 27 8 28 10 17 2,9
2,1
2,1
12 30 9 33 12 19 3,4
2,4
2,4
2 3 2 4 2 2 0,4
0,3
0,3
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
Table 9. (SC3) Mooring lines loads results for the bulk
carrier ship moored at warehouse 39 – Left margin
trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
LM2 L máx 8 11 3 13 7 12
0,9 1,4 0,9
LM5 L máx 4 12 3 13 6 7
1,4 0,9 0,9
LM7 L máx 5 14 3 15 6 8
1,3 1,2 1,0
6 12 3 14 6 9 1,2
1,2
0,9
8 14 3 15 7 12 1,4
1,4
1,0
2 2 0 1 1 3 0,2
0,3
0,1
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
For the exiting passage of the ship L366 through
the right margin on the flow tide condition, the
mooring plan of the berthed ship did not meet the
established requirements, neither for mooring lines
load nor for the ship movements. The more tensioned
mooring lines were the After Breast (AB), Forward
Spring (FV), and the Head (Hd). The ship movement’s
results exceeded the adopted limits for all three
measured freedom degrees.
For tests simulating the ship passing through the
channel center and left margin, farther from the
docking berth, all the mooring line loads and moored
ship motions measurements were below the
established limits.
Like the previous scenarios, the results showed
good consistency, presenting a reduction in mooring
lines loads as the distance between the two ships
increased. In addition, it was possible to observe that
the most tensioned lines (AB, AS, Hd) were the same
for all tested conditions, as presented in Figure 10.
Figure 10. Mean maximum mooring line loads for all the
tested trajectories.
3.4 Scenario 4– Passing ship exiting the port in the ebb
tide
Table 10. Mooring lines loads results for the bulk carrier
ship moored at warehouse 39 – Right margin trajectory
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
RM2 L máx 18 38 11 37 12 21
3,9 2,9 2,5
RM3 L máx 18 41 11 39 11 25
3,7 3,4 2,8
RM5 L máx 21 40 12 38 13 25
3,8 3,2 2,7
19 40 12 38 12 24 3,8
3,2
2,6
21 41 12 39 13 25 3,9
3,4
2,8
2 2 1 1 1 2 0,1
0,2
0,2
Displacement
Mean
máx. máx.
Stan. Deviation
Load (tf)
Table 11. Mooring lines loads results for the bulk carrier
ship moored at warehouse 39 – Channel center trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
CC1 L máx 6 14 2 14 6 8
1,3 1,0 0,8
CC5 L máx 7 14 1 13 3 9
1,1 1,1 0,7
CC7 L máx 5 16 2 14 4 9
1,1 1,2 0,9
6 15 2 14 4 9 1,2
1,1
0,8
7 16 2 14 6 9 1,3
1,2
0,9
1 1 1 1 1 0 0,2
0,1
0,1
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
851
Table 12. Mooring lines loads results for the bulk carrier
ship moored at warehouse 39 – Left margin trajectory.
Test Load St AB AS FS FB Hd Surge (m) Sway (m) Yaw (°)
LM1 L máx 6 9 1 12 2 4
1,0 0,6 0,6
LM5 L máx 6 9 1 10 2 5
0,9 0,6 0,6
LM6 L máx 5 8 1 10 2 5
0,8 0,5 0,7
6 9 1 11 2 5 0,9
0,5
0,6
6 9 1 12 2 5 1,0
0,6
0,7
1 1 0 1 0 0 0,1
0,0
0,1
Load (tf)
Displacement
Mean
máx. máx.
Stan. Deviation
The tests results revealed that the passage of the
ship L366 during its exit from the port at flow tide do
not induce mooring line loads above the established
operational limits in any proposed trajectories. The
ship motions measurements presented values above
the established limit for the sway displacements
during the tests of the trajectory closest to the berth
(right margin). The other trajectories did not yield
ship movements above the adopted limits.
However, it is worth mentioning that the loads
results for the After Breast (AB) and Forward Spring
(FS) are close to the established limit, requiring more
attention to this condition.
Like the previous scenarios, it was possible to
notice a good consistency in the results achieved for
the three simulated trajectories, as illustrate at Figure
11.
Figure 11. Mean maximum mooring line loads for all the
tested trajectories.
The scale model tests results indicate that the
passage of the L366 ship through the right margin
trajectory, entering or exiting the port area, tensioned
the mooring lines of the ship docked in Warehouse 39
above the established limit by OCIMF [5]. In addition,
the movement of the moored ship also remained
above the limits established by PIANC [6]. The worst
scenario for the moored vessel, during the passage of
the L366 in the right margin trajectory, was the entry
in ebb tide condition, where the greatest mooring
lines loads occurred, and more cables presented
values above the recommended limit.
Regarding the trajectories through the channel
center and the left margin, the mooring line loads
always remained within the established limits for all
the tested conditions. The same can be said for the
ship motions measurements obtained in almost all
tests for these trajectories, the only exception being the
scenario of the passing ship navigating through the
channel center at ebb tide when the sway
displacement slightly exceeded the limit established
by PIANC [6].
The results of the entire test series were considered
consistent since it was possible to observe a low
dispersion in the mooring line loads observations
between the repetitions of each simulated condition.
The results also yielded foreseen patterns, as the
reduction in the mooring lines loads and moored ship
movements as the trajectories of the passing ship were
pushed farther from the berth. Moreover, the tests of
the same scenario produced a similar pattern in the
distributions of the mooring lines loads for the three
trajectories simulated, with same lines being the most
tensioned regardless of the ship trajectory.
4 CONCLUSIONS
Regarding the navigation conditions near warehouse
39, a curved sector of the channel, the hardest
maneuver to execute during the tests was the ship
entrance in the Port at the ebb tide condition. Due to
the curvature of the channel, when the vessel
approaches the warehouse 39 the water ebbing to
Santos Bay strikes the L366 ship perpendicularly,
displacing it toward the left margin.
From the point of view of the hydrodynamic
interaction between the L366 and the 125,000 DWT
ship moored at warehouse 39, the scale model results
allowed to conclude that, using the proposed mooring
plan, it is not possible to assure safety in the moored
ship operations when the right margin trajectory is
utilized. These conclusions are based on the criteria
established by the OCIMF [5] and PIANC [6]
recommendations.
In the tests simulating the passage of L366 through
channel center, the only scenario that the moored ship
presented excessive motions was the entrance
navigation at the ebb tide, which is, in fact, the most
critical scenario for the hydrodynamic interaction at
warehouse 39.
Regarding the sceneries with the left margin
trajectory, the tests results did not indicate any
restrictions to the proposed mooring plan, however,
the viability of the channel navigation through this
trajectory must be verified.
The Table 13 summarizes the mooring plans
conditions for each tested scenario. The plan
condition is identified by the colors:
Red: Denotes that the mooring lines loads or ship
motions measurements surpassed the limits
recommended by OCIMF or PIANC It is advised to
not execute the ship passage;
Yellow: Denotes that the mooring lines loads or
ship motions measurements are close to the limits
recommended by OCIMF or PIANC. It is advised to
have great caution with the passage conditions;
Green: Denotes that the mooring lines loads or
ship motions measurements are within the limits
recommended by OCIMF or PIANC. None
restrictions to ship passage were indicated by the
tests.
852
Table 13. Summary of the mooring plan conditions for each
test.
Scenario
Condition of
passage
Condition of
tide
Trajectory
Condition
mooring plan
RM
CC
LM
RM
CC
LM
RM
CC
LM
RM
CC
LM
3
Exit
Flood
4
Exit
Ebb
1
Entrance
Flood
2
Entrance
Ebb
It is noteworthy that the tests can be
complemented with new studies in scale model to
optimize the proposed mooring plan, in order to try
to mitigate the operational restrictions identified in
this paper. In the new tests would be possible to
evaluate the utilization of mooring lines composed by
different materials, mooring plans with more lines,
new mooring structures, or even modify the vessels
characteristics, like the draft, aiming to determine the
conditions that ensure a greater safety to ship's
passages in the warehouse 39.
Finally, it is important to highlight that these tests
aimed to evaluate the hydrodynamic interaction of the
ship L366 with a ship moored in the warehouse 39 for
three predefined passage trajectories. It was not the
objective of this study to evaluate the technical
feasibility of these maneuvers (trajectories), especially
because these tests were not performed with the pilots
participation, who are professionals qualified to make
evaluations of this nature.
REFERENCES
1. American Society of Civil Engineers (ASCE): Manual
and Reports on Engineering Pratice No.129: Mooring of
Ships to Piers and Wharves. , Virginia (2014).
2. Bernardino, J.C.M.: Experimental approach for the
evaluation of vessel maneuvers in scale models of
nautical spaces. University of São Paulo (2015).
3. Flory, J.F.: A Method for Estimating Passing Ship Forces.
Presented at the Ports Conference 2001 , Norfolk,
Virginia, United States April 29 (2001).
https://doi.org/10.1061/40555(2001)48.
4. Fundação Centro Tecnológico de Hidraúlica (FCTH):
Estudos em modelo físico para avaliação do efeito da
interação hidrodinâmica no Armazém 39. RELATÓRIO
TÉCNICO (RT) N
o
05. , Laboratório de Hidráulica da
Escola Politécnica da USP. São Paulo (2018).
5. OCIMF: Mooring equipment guidelines. , London, UK
(2013).
6. PIANC: Report of Working Group no. 24. , Brussels
(1995).