Numerical Investigation on the Scharnov Turn Maneuver for ...

Numerical Investigation on the Scharnov Turn Maneuver for Large Vessels

Original article

Vol.5 No.1, 2020 Transactions of Navigation 17

Numerical Investigation on the Scharnov Turn Maneuver for

Large Vessels

Qianfeng JING1, Kenji SASA2, Chen CHEN2, Xianku Zhang1, Yong YIN1

1Dalian Maritime University, China

2Kobe University, Japan

Abstract

To improve the adaptability of the Scharnov turn maneuver of large vessels, numerical simulations of the traditional

and revised Scharnov turn are performed on different vessels. The maneuvering model based on the MMG standard

method is adopted. The results show that the traditional maneuver is not suitable for large vessels because of their

different turning abilities. According to navigation experience and simulation results, selecting a new control angle ψ2

of around 220° with ψ1 no change or new control angle ψ1 of about 280° with ψ2 no change is recommended to modify

the traditional maneuver. The revised maneuvers can be effectively applied to large vessels under “man overboard”

emergency situations. The simulation tests illustrate that, on average, the revised maneuver can reduce the lateral

distance by 92.3%.

Keywords: Emergency maneuver, Man overboard, Ship maneuverability, MMG model, Numerical simulation

1. INTRODUCTION

Man overboard is a dangerous situation for a vessel at sea.

Accidents related to men falling overboard are among the

many threats that could undermine the proper course of the

voyage of a vessel. Unfortunately, most overboard incidents

result in death. Therefore, it is very important for crews to

perform appropriate recovery methods to effectively save the

life of a person in water. The Scharnov turn maneuver is widely

used to bring a ship back to its previous position. It is the most

appropriate maneuver when the position to be reached is

significantly further astern compared with the vessel turning

radius1). It was developed by and named after Ulrich Scharnov.

With the development in the shipbuilding industry, the size

of vessels has rapidly become larger. Numerical analyses have

shown that the special maneuvering characteristics of large

vessels should be considered in practice2). However, few

studies focus on the maneuvering behavior of vessels with

different scales under an emergency maneuver. Zhang3)

analyzed the Williamson turn of very large carriers, and the

results of the simulation test demonstrated the problem of the

traditional maneuvering procedure. He proposed an improved

maneuver scheme, which could be well applied to the

Williamson turn for very large carriers. Nevertheless, the

Scharnov turn was not discussed in his work. Baldauf4)

developed ship rapid-simulation software and conducted

simulation tests of a ship emergency maneuver to find some

better maneuvering solutions. However, no specific ship

maneuvering recommendations were proposed from his

simulation results.

Inspired by the aforementioned works, the present study

analyzes the Scharnov turn of different vessels. The

hydrodynamic coefficients of ten vessels with different scales

are collected to conduct the investigation. The vessels are

divided into two groups: small vessels with a ship length of less

than 140 m and large vessels with a ship length of more than

270 m. Because of the high cost and safety factors of a

real-environment ship test, numerical simulation is an effective

alternative to perform research. A three-degree-of-freedom

maneuvering model based on the maneuvering model group

(MMG) standard method is employed in this study to

numerically simulate the Scharnov turn maneuver of the ten

vessels. The effect of environment is temporarily not

considered. The simulation results show that the traditional

Scharnov turn maneuver can make small vessels return to the

original track line, although this is not possible for large vessels.

In addition, more simulations have been conducted to study the

effect of different control angles. Two revised maneuver

schemes are proposed and verified with sufficient simulations.

The structure of this paper is as follows: Section 2 describes

the procedure of the standard Scharnov turn, Section 3

introduces the MMG standard method, and Section 4 presents

the numerical simulations and results. Section 5 discusses the

special maneuvering characteristics of large vessels, and two

methods are proposed to improve the Scharnov turn. Section 6

presents the conclusions of this study.

Correspondence to Qianfeng JING: The Graduate School of Maritime

Sciences, Kobe University, 5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe,

658-0022, Japan; E-mail: [email protected]

Jing, Q., Sasa, K., Chen, C., Zhang, X., and Yin, Y.

Original article

18 Transactions of Navigation Vol.5 No.1, 2020

2. SCHARNOV TURN

The International Aeronautical and Maritime Search and

Rescue (IAMSAR) Manual was first published by the

International Maritime Organization in 1998, in association

with International Civil Aviation Organization, and is annually

revised5). The standard methods for recovery in rescuing a man

overboard include the “Single turn,” “Williamson turn,” and

“Scharnov turn.” The Scharnov turn procedure is shown in Fig.

1 and described in details as follows:

0°0°

Port Starboard

1 240 =

2 200 =2 160 =

1 120 =Begin

End

180end =

Fig. 1 Scharnov turn maneuver

(1) Rudder hard over. If in response to a man overboard, put

the rudder toward the person. It is the beginning of the

Scharnov turn procedure.

(2) After deviating from the original heading by

approximately 240°, the heading angle, denoted as ψ1,

shifts the rudder hard to the opposite side.

(3) When heading at approximately 20° short of the

reciprocal heading, the heading angle, denoted as ψ2, put

the rudder amidship so that the vessel will turn to the

heading opposite the original track line.

(4) The Scharnov turn procedure is then ended when the

heading is equal to the opposite value of the heading at the

beginning of the maneuver.

3. SHIP MANEUVERING MODEL

3.1 Model Structure

The MMG model is widely used for simulating the ship

maneuvering motion6). In the present study, the MMG standard

method is adopted to analyze the Scharnov turn maneuver7).

The employed coordinate systems are shown in Fig. 2. The

space fixed coordinate system is o0–x0y0z0, and the moving-ship

fixed coordinate system is o–xyz.

y

x

u-vm

U

o

x0

o0y0

r

δ

ψ

Fig. 2 Coordinate systems

The maneuvering motions of a ship are described as surge,

sway, and yaw. The maneuvering model used for the numerical

simulations are expressed as

2

2

( ) ( )

( ) ( )

( ) ( )

x y m G H R P

y m x G H R

zG G z G m H R

m m u m m v r x mr X X X

m m v m m ur x mr Y Y

I x m J r x m v ur N N

+ − + − = + +

+ − + + = +

+ + + + = +

. (1)

Eq. (1) represents the differential equations to be solved,

where u, vm, r, ψ, x0, y0, and δ are the state variables that denote

the velocity components in the x and y directions, heading

angle, yaw rate, position components in the x0 and y0 directions,

and rudder angle. Subscript X, Y, and N denote the surge force,

lateral force, and yaw moment, respectively. The

hydrodynamic force is separately calculated, where H is the

hydrodynamic force acting on the hull, R is the hydrodynamic

force due to steering, and P is the hydrodynamic force due to

the propeller. The added mass mx, my and the added moment of

inertia Jz, the moment of inertia IzG were estimated with the

charts given by Motora8)9)10).

The hydrodynamic forces acting on a ship hull are expressed

as follows:

2

02

2 4

3

2

2 2 3

3

2 2

2 2

1

2

1

2

1

2

vv m vr m

H pp

rr vvvv m

v m r vvv m

H pp

vvr m vvr m rrr

v m r vvv m

H pp

vvr m vrr m

R X v X v rX L dU

X r X v

Y v Y r Y vY L dU

Y v r Y v r Y r

N v N r N vN L dU

N v r N v r

− + += + +

+ += + + +

+ +=

+ + + 3

rrrN r

(2)

The forces are expressed as the first-, third-, and fourth-order

polynomial functions of the state variables. The coefficients of

each state variable are the hydrodynamic derivatives of

maneuvering. The hull resistance R0 was calculated by the

Holtrop method11). The nonlinear coefficients in XH were

estimated based on Matsumoto method12). Both the linear and

nonlinear coefficients in YH and NH were estimated by the

regression formula of Kijima13) and Lee14)

The surge force due to the propeller is expressed as


Original article


( )

( )

( )( )

2 4

0

2

2 1 0

0

(1 ) ( )

, 1

exp 4.0

p P p P T P

T P P P

P

P P P

P P

P P P

X t n D K J

K J k J k J k

uJ u u w

n D

w w x r

= −

= + +

= = −

= − −

(3)

Where nP is the propeller rate, tP0 is the deduction factor

estimated by Harvald method15), KT is the propeller thrust

coefficient calculated by second order polynomials of the

propeller advance ratio (JP). WP0 is the wake factor estimated

by Kijima method13). xP ́ is the non-dimensional propeller

position which is set -0.5 in the present study.

The effective rudder forces are expressed as

( )

( )

2 2

2

2

2

(1 ) sin

(1 ) cos

( ) cos

,

81 1 1 1

0.5 sin

R R N

R H N

R R H H N

R R R R R R

T

R R P R

P

R P

N R R

R R

X t F

Y a F

N x a x F

U u v v U l r

Ku u

J

v DF A U f

u H

= − −

= − +

= − +

= + = −

= + + − + −

= − =

，

(4)

Where the tR, aH and xH are the coefficients representing

hydrodynamic interaction between ship hull and rudder. The

The γR and lR´ are flow straightening factors due to lateral speed

and yaw rate. The rudder normal force coefficient fα is

estimated by Fujii method16). The UR and αR are the rudder

inflow velocity and angle. Where HR is the rudder span length,

tR, aH, xH, and the constant εR are estimated by Kijima13) method.

The coefficient κR is estimated according to Yoshimura17).

After deriving the expression of the state variables in the

differential equations, the final equations to be solved are

expressed in Eq. (5). Note that v = vm + xGr, and δE, TE is the

executed rudder angle and the steering gear time constant,

which is taken as 2.5s in the present study.

( )

( )

( )

( ) ( )

( ) ( )

( )

0

0

, , , , , , , ,

, , , , , , ,

, , , , , , , , ,

cos sin

cos sin

/

x y m G H R P

x y G H Rm

x y zG m G H R

E E

f m m m v r x X X Xu

f m m m u r x Y Yv

r f m m m I u v r x N N

rx

u vy

v u

T

=

− + −

(5)

The fourth-order Runge–Kutta method is adopted to solve

the aforementioned differential equations considering

efficiency and accuracy. In simulating the maneuvering motion

of the vessels, the initial state is first defined with hard rudder to

the man-overboard side. Then, iterative calculation is

performed using the fourth-order Runge–Kutta method. The

state variables calculated in each step are recorded. When the

vessel heading achieves ψ1, a reverse-rudder order is issued.

When the heading reaches ψ2, an amidship-rudder operation is

performed. The simulation flowchart is shown in Fig. 3.

Detailed discussion of the MMG model is beyond the scope of

the present study.

Iteration

( )1 _ 4k kRungeKuttaX X+ =

2 & 1k flag = =

Record

( )0 0, , , , , , ,mt u v r x y

Rudder

MAX = −

1flag =

( )0 0 0, , , , , , ,mX t u v r x y =

Initial State

MAX =initialu u= 0flag =

1 & 0k flag = =

Rudder

0 =

Yes

No

Yes

No

finalt t=

Yes

No

Fig. 3 Flowchart of the Scharnov turn maneuver simulations

3.2 Model Validation

To validate the simulation model, the sea-trial data of

“HuaiJiHe” and the model test data of “KVLCC2” are used for

comparative experimental study. The basic parameters of the

two vessels are listed in Table 1. We note that vessel

“HuaiJiHe” is a small vessel, whereas “KVLCC2” are large

vessels according to the definitions in the Introduction section.

Table 1 Basic Ship Parameters

HuaiJiHe KVLCC2

Lpp (m) 114.0 320.0

B (m) 20.5 58.0

dm (m) 4.385 20.8

▽ (m3) 6859.07 312600.0

Cb 0.653 0.810

xg (m) 2.0 11.2

Dp (m) 4.5 9.86

AR (m2) 17.95 112.5

V (knot) 15.9 15.5

δ (°) 35.0 35.0

The simulations of the turning circles and zig-zag maneuvers

are shown in Fig. 4a, 4b, 4c, and 4d. The simulation results are

in good agreement with the test data. Note that the results of

model experiments were transformed into the actual ship scale.


Original article


Fig. 4a Turning circle of HuaiJiHe

Fig. 4b Turning circle of KVLCC2

Fig. 4c Zig-zag ±10/±10 of HuaiJiHe

Fig. 4d Zig-zag ±20/±20 of KVLCC2

Table 2a Comparison of the Turning Indexes

HuaiJiHe KVLCC2

AD DT AD DT

Port

Test 319.7 451.3 1040.0 1068.8

Sim. 305.0 430.2 1085.1 1117.2

Error 4.60% 4.67% 4.34% 4.53%

Star-

board

Test 302.5 392.1 995.2 985.6

Sim. 315.6 372.5 1097.3 1118.0

Error 4.33% 5.00% 10.26% 13.43%

Table 2b Comparison of the Overshoot Angles

HuaiJiHe KVLCC2

1st OSA 2nd OSA 1st OSA 2nd OSA

Port

Test 3.42 3.17 13.7 15.3

Sim. 1.86 1.61 9.74 9.67

Dif. 1.56 1.56 3.96 5.63

Star-

board

Test 2.33 2.26 15.1 13.4

Sim. 1.78 1.46 9.79 13.64

Dif. 0.55 0.80 5.31 0.24

The turning indexes and the overshoot angles of the two

vessels are compared and listed in Tables 2a and 2b. The

maximum relative error between the numerical simulations and

test data is 13.43% in turning circles. In addition, the maximum

absolute difference of overshoot angles between the numerical

simulations and test data is 5.63° in zig-zag maneuvers.

Although the simulation results could not be fully consistent

with the test results. It is verified that the adopted mathematical

model is able to predict the maneuvering motion of both small

and large vessels. The research precision is satisfactory.

4. SIMULATION RESULTS

In this section, the numerical simulations of the Scharnov

turn maneuver to evaluate the influence of the vessel scale are

presented. Using the validation presented in the previous

section, we believe that the selected model can simulate the

maneuvering motion of both large and small vessels. To obtain

a more general conclusion, four large and four small vessels are

added into the simulations in the succeeding simulation test and

modeled using the same method. The vessel parameters used in

the simulations are listed in Table 3.

The traditional Scharnov turn of both the small and large

vessels is simulated based on the maneuvering model. In

addition, the man-overboard situation at both starboard and

port sides is taken into consideration. The simulation results

from the starboard side are shown in Figs. 5 and 6, and those

from the port side are shown in Figs. 7 and 8. The endpoints of

each simulation have been marked by triangles.


Original article


Table 3 Basic Parameters

Cargo Yukun Yulong Century

Paragon

Lpp (m) 99.0 105.0 126.0 132.0

B (m) 16.0 18.0 20.8 19.0

dm (m) 6.5 5.4 5.6 2.9

▽ (m3) 7794.8 5591.3 14278.1 12516.0

Cb 0.703 0.559 0.681 0.821

xg (m) -2.0 -0.8 0.63 0.22

Dp (m) 3.2 4.0 4.6 6.1

AR (m2) 12.2 11.8 18.8 25.15

V (kn) 13.7 16.7 13.6 12.9

ZYCQ Cosgreat

Lake

DaMing

Lake OPALIA

Lpp (m) 320.0 320.0 274.7 320.0

B (m) 60.0 60.0 48.0 60.0

dm (m) 20.8 20.9 17.3 22.09

▽ (m3) 344270.0 344300.0 185978.0 313726.6

Cb 0.826 0.828 0.883 0.826

xg (m) 2.0 -2.0 2.0 2.0

Dp (m) 9.6 9.6 8.3 10.3

AR (m2) 109.7 108.4 108.0 97.3

V (kn) 15.6 15.6 13.7 16.8

Figs. 5 and 7 show that the traditional maneuver can bring

the vessels to the opposite heading in the five small vessels at

both sides. However, the same does not work well for the five

large vessels, as shown in Figs. 6 and 8.

One of the possible reasons for this result is that the

traditional maneuver has been established for decades and the

reference types of the vessels is mostly similar to the five small

vessels. With the development in the shipbuilding industry, the

sizes of the vessels have become larger, and the

maneuverability has changed, which make the traditional

maneuver no longer applicable.

To understand this problem, further numerical simulations

are carried out under different control angle ψ2 and ψ1. Initially,

vessel OPALIA is considered as an example to perform

Scharnov turn simulations at both sides under different control

angle ψ2 with a constant ψ1 (port = 120°, starboard = 240°), as

shown in Figs. 9 and 10.

Figs. 9 and 10 show the different control angles that lead to

different distances. Although a slight difference exists between

the simulation results of the port and starboard sides, the lateral

distance of the original track line reduced significantly from

230° to 200°. Moreover, the lateral distances become larger

again when control angle ψ2 is less than 200°. The reasons for

the difference between the simulation results at the port and

starboard sides involve several factors, which are discussed in

Section 5.

Fig. 5 Traditional Scharnov turn of the small vessels

(Man overboard starboard side)

Fig. 6 Traditional Scharnov turn of the large vessels



Original article


Fig. 7 Traditional Scharnov turn of the small vessels

(Man overboard port side)

Fig. 8 Traditional Scharnov turn of the large vessels


Fig. 9 Comparison of the different control angles for OPALIA


As a summary, the trajectory of the traditional maneuvering

scheme (control angle ψ2 = 220°) is far from the original track

line. Large vessel OPALIA almost returns back to the original

track line at both sides when control heading angle ψ2 is

selected as approximately 40° short of the opposite heading.

Fig. 10 Comparison of the different control angles for OPALIA



Original article


To evaluate this phenomenon on other large vessels, similar

simulation procedures are carried out on the remaining four

large vessels to evaluate the influence of the different control

angles. The simulation results are shown in Figs. 11–14.

Fig. 11 Comparison of the different control angles for DaMing

Lake

Fig. 12 Comparison of the different control angles for ZYCQ

Fig. 13 Comparison of the different control angles for Cosgreat

Lake

Fig. 14 Comparison of the different control angles for KVLCC2

Figs. 11–14 show that the simulations of the Scharnov turn

maneuver from 190° to 230° control angles ψ2 (at a 5° interval)

demonstrate the variance of the different lateral distances. In

addition, the same conclusions can be drawn that the traditional

maneuvering scheme (control angle ψ2 = 220°) can hardly

bring the large vessels to the original track line because of the

large lateral distance. The lateral distances to the original track

line reach a relatively small value around control angle ψ2 that

is 40° short of the reciprocal heading. To further illustrate the

relationship between the control angles and lateral distances,

the lateral distances in each simulation are recorded and shown

in Fig. 15.

Fig. 15 Lateral distances under different control angles ψ2

The different lateral distances when the control angle

changes from 190° to 225° are shown in Fig. 15. We need to

emphasize that almost all large vessels cannot return to the

reverse heading at control angle ψ2 = 230°. Thus, the distances

at 230° are not listed. Meanwhile, the simulation data clearly

show that the lateral distances are very large at control angle ψ2

= 225°. Large vessels have difficulty returning opposite to the

original heading when control angle ψ2 is more than 225°. To

obtain more information about the tendency of the lateral


Original article


distances resulting from the control angle, a 5° interval is

selected. The lateral distances reach a minimum at a control

angle ψ2 of approximately 220° in all large vessels. Moreover,

we can conclude that control angle ψ2 is a vital factor in the

Scharnov turn maneuver. It significantly influences not only the

final heading angle but also the lateral distance during the

maneuver, which should be carefully considered in a search

and rescue in a man-overboard situation. The simulation results

show that changing the control angle ψ2 can bring the large

vessels back to the original track line as early as possible.

Revised control angle ψ2 is approximately 40° short of the

opposite heading. The simulations under control angle ψ2 =

220° at both sides of all large vessels are shown in Figs. 16 and

17.

We quantitatively evaluate the change in the trajectory

before and after changing the control heading angle. Table 4

lists the absolute value of the lateral distances from the original

track line when the vessels reach the opposite heading, where

dts´ represents the distances of the traditional maneuver at the

starboard side and drs ́denotes that of the revised maneuver at

the starboard side. In addition, dtp ́and drp ́convey the same

meanings with respect to the port side. In addition, all listed

distances are non-dimensionalized by the ship length for easy

comparison.

Table 4 Comparison of the Distances from the Original Track

(Revised ψ2 is 40° short of the opposite heading)

ZYCQ Cos. OPA. KVL. DaM. Avr.

Lpp 320.0 320.0 320.0 320.0 274.7 310.9

dts ́ 2.16 1.91 0.92 1.68 1.69 1.67

drs ́ 0.23 0.24 0.09 0.07 0.14 0.15

dtp ́ 1.99 1.83 0.90 1.47 1.62 1.56

drp ́ 0.09 0.10 0.11 0.12 0.05 0.09

To further investigate the influence of the other control

angle ψ1, similar procedures have been conducted under

different ψ1 with a constant ψ2 (port = 160°, starboard = 200°).

The different lateral distances when the control angle ψ1

changes from 230° to 290° are shown in Fig. 15. The lateral

distances reach a minimum at a control angle ψ1 of

approximately 280° in all large vessels. Revised control angle

ψ1 is approximately 40° bigger than the traditional ψ1. The

simulations under control angle ψ1 = 280° at both sides of all

large vessels are shown in Figs. 19 and 20. Table 5 lists the

absolute value of the lateral distances from the original track

line when the vessels reach the opposite heading.

For the traditional maneuver scheme, the results show that

the average lateral distances in the original track line of the

starboard- and port-side maneuvers are 1.67L and 1.56L,

respectively. For large vessels with a ship length of

approximately 300 m, a distance of more than 484.5 m (1.615L,

on average) results in search and rescue difficulties.

Table 5 Comparison of the Distances from the Original Track

(Revised ψ1 is 40° more than traditional ψ1)

ZYCQ Cos. OPA. KVL. DaM. Avr.

Lpp 320.0 320.0 320.0 320.0 274.7 310.9

dts ́ 2.16 1.91 0.92 1.68 1.69 1.67

drs ́ 0.14 0.17 0.17 0.01 0.13 0.12

dtp ́ 1.99 1.83 0.90 1.47 1.62 1.56

drp ́ 0.03 0.20 0.18 0.12 0.17 0.14

Fig. 16 Numerical simulations of the revised Scharnov turn

(Revised ψ2, Starboard side)

However, in the revised scheme, the average distances after

the modification of the control angle ψ2 are reduced to 0.15L

for the starboard side and 0.09L for port side, and the average

distances after the modification of the control angle ψ1 are

reduced to 0.12L for the starboard side and 0.14L for port side.

To more intuitively explain this problem, Fig. 21 shows the

target search range of a man-overboard situation. The gray

shaded portion approximately shows the area that needs to be


Original article


searched.


(Revised ψ2, port side)

Fig. 18 Lateral distances under different control angles ψ1


(Revised ψ1, Starboard side)


(Revised ψ1, port side)


Original article


1.56L

1.67L

0.09~

0.12L

0.14~

0.15L

Fig. 21 Lateral distance of the search and rescue

For the traditional Scharnov turn maneuver, the crews need

to concentrate on a relatively large searching range considering

the lateral distances of large vessels. For the crews, visual

searching over such a large range without the help of a

helicopter is difficult. However, if the revised maneuvering

scheme is applied, the lateral distance is determined in the

average range of 0.09 ~ 0.15L, which is a reduction of 92.3%,

on average. Compared with the traditional maneuver, the

revised maneuver will be closer to the original track line when

the opposite heading is reached, which is more conducive for

searching a person overboard and carrying out rescue

operations.

5. DISCUSSION

The essential reasons for the simulation results are discussed

in this section. Initially, the block coefficients of the five large

vessels are relatively large, which means that the hull is closer

to the cuboid. There are four small vessels with small block

coefficient and one small ship with a block coefficient of more

than 0.8, the simulation results keep consistent between these

small ships. That is, not only the block coefficients, but ship

length could influence the Scharnov turn maneuver. From the

perspective of navigation experience, ships with hypertrophic

hull structure have the characteristics of poor rudder effect,

poor course stability, and good turning ability. However,

compared to the turning ability of large vessels, the inertia

forces of a small vessel could be relatively small even with a

large block coefficient. All these characteristics influence the

behavior of vessels in the Scharnov turn maneuver.

The simulation test results show a slight difference at the

starboard and port sides. One of the possible reasons for this

phenomenon is that the viscous hydrodynamic force acting on

the hull is different when the ship has a negative or positive

lateral speed. In addition, the traditional Scharnov turn

maneuver is effective for small vessels but remains too far

away from the original track line for large vessels. Through

simulations using different control angles ψ2, the better timing

of rudder amidship is approximately 40° short of the opposite

heading. To verify this idea, the same simulations are carried

out on all large vessels. We verify that the modification

obviously reduces the distances from the original track line,

which is convenient for the crew on board to search a person

that falls in the water. Additionally, simulations under different

control angle ψ1 have also been performed. It is verified that

changing ψ1 could bring the large vessels to the opposite

heading as well. From Fig. 19 and 20, it is obvious to see that

the vessels will reach to the reverse heading more quickly

when only changing ψ1 compared to the situation of only

changing ψ2. Furthermore, this conclusion is also consistent

with the above-mentioned navigation experience. According to

the aforementioned analysis, two recommendations are

proposed to modify or change the Scharnov turn in IAMSAR.

For large vessels, especially for those with large block

coefficient and large ship length, the maneuver should be

revised by selecting the control angle ψ2 approximately 220°

(40° short of the opposite heading) with ψ1 no changed, or

control angle ψ1 approximately 280° (40° bigger than the

traditional ψ1) with ψ2 no changed which is coincident to the

special characteristics of ships.

6. CONCLUSIONS

In this paper, problems related to the Scharnov turn for

different vessels have been discussed. From the numerical

simulations of the Scharnov turn using the ship maneuvering

model based on MMG, the special characteristics of large

vessels resulting from different turning abilities are illustrated.

Results indicate that the traditional Scharnov turn maneuver is

no longer suitable for large vessels. Through the numerical

investigation of a Scharnov turn of large vessels at different

control angles ψ2 and ψ1, two important conclusions can be

obtained. First, control angle ψ2 and ψ1 are some of the key

factors in the Scharnov turn maneuver. It obviously changes the

lateral distance and final heading angle of the maneuver. Then,

for large vessels, either changing ψ1 or ψ2 independently will

bring the vessels to the original track line. Furthermore, the

lateral distance reaches a minimum at approximately 220° of

ψ2 and 280° of ψ1. However, the revised maneuver of changing

ψ1 is faster to reach the reverse heading compared with

changing ψ2. In addition, two recommendation to change the

Scharnov turn are proposed to handle a “man overboard”

emergency situation. The simulation results verify the

effectiveness of the modification on the traditional maneuver.

The recommendations can be exactly useful in practice for the

Scharnov turn of large vessels. Other emergency maneuvers

for man-overboard situations are not included in this study, and

the effect of the environment is not considered in the

maneuvering model. These factors can be discussed in the

future.

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8. AUTHOR’S BIOGRAPHY

Qianfeng JING is a Ph.D. candidate in Transportation

Information Engineering and Control from Dalian

Maritime University, China. He is currently an Exchange

Student at Kobe University, Japan.

Kenji SASA received the Ph.D. degree in Mercantile

Marine from the Kobe University of Mercantile Marine

in 2002. He is currently an Associate Professor of the

Department of Maritime Sciences, Kobe University,

Japan.

Chen CHEN received the Ph.D. degree in Engineering

from Kobe University in 2016. He is currently an

appointed Assistant Professor of the Department of

Maritime Sciences, Kobe University, Japan.

Xianku ZHANG received the Ph.D. degree in

Transportation Information Engineering and Control

from Dalian Maritime University, China, in 1998. He is

currently a Professor at the Key Laboratory of Maritime

Simulation & Control, China.

Yong YIN received the Ph.D. degree in Transportation

Information Engineering and Control from Dalian

Maritime University, China, in 2001. He is currently a

Professor at the Key Laboratory of Maritime Simulation

& Control, China.

Date received May 20, 2019

Date revised Sept. 20, 2019

Date accepted Dec. 13, 2019

Date post:	18-Dec-2021
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