Description of "Resistance" - "Propeller" and Hydrostatic calculations for ship design purposes on a IBM compatible PC. Part 1, Including Appendix 1 untill 5
PORIZT2
Ing. A.P. de Zwaan Report nr. 858 January 1990
Delft University of Technology
Ship Hydromechanics Laboratory Mekelweg 2
2628 CD Defft The Netherlands Phone 015 - 78 68 82
INDEX.
page Summarv.
Computer configuration needed
A. Start of the general
menu.2 1. Still water resistance according to HOLTROP and MENNEN.
3 1.1 Introduction. 3 1.2 Input menus. 1.2.1 First window. 3 1.2.2 Second window. 4 1.2.3 Third window. 4 1.3 Menu handling keys.
5
2. Resistance calculation
according to GULDHAMMER and HARVALD.6 2.1 Introduction. 6 2.2 Input menus. 6 2.2.1 First window. 6 2.2.2 Second window. 7 2.2.3 Third window. 7
2.3 Menu handling keys.
7
3. Resistance calculation according to LAP /W.H. AUF'M
KELLER. 8 3.1 Introduction. 8 3.2 Input menus. 8 3.2.1 First window. 8 3.2.2 Second window. 8 3.3 Menu handling keys.9
4. Calculation of
Wageningen B-Serie Propellers,10 4.1 Introduction, 10 4.2 Input menus. 10 4.2.1 First window. 11
4.4.2 Second window
(optional).11
4.3 Menu handling keys.
12
5. Calculation of
Ducted Propellers.13 5.1 Introduction. 13 5.2 Input menus. 13 5.2.1 First window. 14
5.2.2 Second window
(optional).14
5.3 Menu handling
keys.3
INDEX (continued)
Page
6. Hydrostatic programs. 16
6.1 Introduction. 16
6.2 Input menus. 16
6.2.1 Menu for the general input data. 17
6.2.2 Menu distances between calculation
ordinates. 176.2.3 Menu for the hullform
cross sections. 186.3 Menu handling keys. 19
6.4 Menu for the calculation
programs. 206.4.1 Check input data and modify. 20
6.4.2 Input control by plotting the
body plan on screen. 206.4.3 Displacement calculation. 21
6.4.4 Stability calculation. 21
6.4.5 Trim calculation. 22
6.4.6 Floodable length curve calculation. 23 6.5 Menu handling keys.
Summary
This report describes how to use and start the several programs,
and does not give a description of the theory
used.For the description of used methods an appendix is given at the end of this report or references are made.
The programs are
a). Resistance calculation according
to "HOLTROP and MENNEN".Resistance calculation according to "GULDHAMMER
and HARVALD".Resistance calculation according to "LAP /
AUF'M KELLER".Calculation of "WAGENINGEN B-SERIE
PROPELLERS".Calculation of "DUCTED PROPELLERS".
Hydrostatic programs consisting of
- input check by a body plan on the
screen or plotter
-
displacement calculation
- stability calculation-
floodable length curve calculation
- trim calculation
The programs are fully
menu controlled and the menu will be activa-ted by the command START <cr>.There are two possibilies for file handling
-
Load an existing file, rectify
possible errors in the input and run.
- Make a new file and run.
The descriptions of the menus will be found in the
corresponding
chapters.
Computer configuration needed:
- IBM compatible MS-dos computer
- Memory 640 Kb
- 20 Mb Hard disk
- 8088, 8086, 80286 or 80386 processor
- Corresponding mathematical coprocessor 8087, 80287 etc. - Graphics screen CGA,EGA,VGA,Hercules or Olivetti screen. - DMP Series Digital Plotter
Houston Instument - Printer
If no plotter is available it is possible
to make a copy of the bo-dyplan on the printer by pressing the print screen key <SCRPRT>.
The menu programs
are written in Quick Basic,version 4.00b and
the calculationprograms in Fortran 77 and compiled
with the IBM
Professional Fortran compiler
of Ryan Mc Farland version 4.2.A. Start of the general menu
Type the command "START" and the following
menu will appear on the screen:Calculation programs.
You may select one of the following
programs:1 Resistance calculation according
to "HOLTROP and MENNEN".2 Resistance calculation according
to "GULDHAMMER and HARVALD".3 Resistance calculation according
to "LAP / AUF'M KELLER".4 Calculation of "WAGENINGEN B-SERIE
PROPELLERS".5 Calculation of "DUCTED PROPELLERS".
6 Hydrostatic programs (input check, displacement, stability, floodable length curve and trim calculation).
7 Stop.
MAKE YOUR CHOICE!
Co with the cursor to the desired
command line and press the return key.The program asks for an existing dataset. If not the program starts with an empty menu, if so the menu will be filled with the values from the existing dataset.
When choosing the numbers 1
until 5 ,after carrying out the
calculation, the program always returns to this menu above. If a wrong choice has been made it is possible to return to
the menu with the <ESC> function
key.1
Still water resistance according to HOLTROP
and MENNEN. 1.1 IntroductionThe still water resistance calculation
is based on the follo-wing reports:A statistical power prediction method,
by
Holtrop J. and Mennen G.G.J.,
International Shipbuilding Progress Vol. 25, October 1978.
See appendix [1].
An approximate power prediction method,
by
Holtrop J. and Mennen G.G.J.,
International Shipbuilding Progress, Vol. 29, July 1982.
See appendix [2].
A statistical re-analysis of resistance and propulsion
data, by
Holtrop J.,
International Shipbuilding Progress, Vol. 31, November 1984.
See appendix [3]. 1.2 Input menus
There is one input menu divided over three windows:
1.2.1 First window
Length between perpendiculars (m) LPP
Length of the construction
waterline (m) LWLMoulded Breadth (m) BR
Midship draft (m) DRAFT
Trim (m)
TRIM
Moulded volume of displacement
(m3) VOLCenter of buoyancy forward of LPP/2 (% of LPP) LCB
Waterplane area coefficient
(-) CWPMidship section coefficient
(-) CMWetted area hull (m2) (if
unknown : SHULL=0) SHULLShape coefficient aft (-)
U-form with Hogner stern : CAFT=+10.0
Normal form CAFT- 0.0
V-form : CAFT--10.0
Pram with gondola:
CAFT=-25.0. CAFT
Wetted area rudder (m2).) SRUD
Rudder coefficient (-)
Rudder behind skeg
CRUD-1.5-2.0Rudder behind stern
. . . . CRUD-1.3-1.5Twin-screw balance rudders CRUD= 2.8 . CRUD
Wetted area appendages (m2) SAPP=SUM[sapp(i)]
SAPP
If the values are entered then ask for next window with the the key <PgDn> (page down).
1.2.2 Second window
Equivalent appendage factor (-)
CAPPSUM[capp(i)*sapp(i)]/SUM[sapp(i)]
Shaft brackets :capp(i)
3.0Skeg :
capp(i) 1.5-2.0
Strut bossings :
capp)i)
3.0Hull bossings : capp(i)= 2.0
Shafts :
capp(i) 2.0-4.0
Stabilizer fins: capp(i)
2.8Dome : capp(i)= 2.7
Bilge keels :
capp(i)
1.4 CAPPCross section area bulbous bow (m2) ABULB
Centroid of bulbous bow cross section
to keel(m) HBULB Diameter of bow thruster tunnel (m)N bow thrusters :
DBTTDBTT*sqrt(N)
. . DBTTResistance coefficient of bow thruster
tunnelThruster in cylindrical part of bow
: CBTT-0.003Thruster at the worst location
: CBTT-0.012 CBTTArea of immersed transom (m2) AT
Length of the run (m) (if unknown
SLR-0) . . SLRAngle of entrance of waterline(if. unknown 0 degr)--ALFA
Number of propellers:0-2,if<>0
calc. of W,T,RRE NPROPIf the values are entered then
ask for next window with the key <PgDn> (page down).1.2.3 Third window
Diameter of propeller (m) DP
Expanded blade area ratio AAE
Pitch-diameter ratio PPD
Number of ship speeds (max) 25) NV
NR. SHIP SPEED NR.
SHIP SPEED
knots knots
etc.
If the input is completed
start calculation with the func-tion key <END>.The program asks: Store data
input? Y(es)/N(o):- Yes :
Name of the dataset (without
extension):
Type a name with not more than seven characters. The input data will be saved on disk under the
en-tered name with the extension ".HLT".
For the calculation
program, the dataset is copied
into a dataset "REKEN.DAT".No : The input data will not be saved on disk.
For the calculation program, the input data will be stored into a dataset "REKEN.DAT".
1.3 Menu handling keys
The following keys are used for
menu handling: <Home> -<Arrow up> -<PgUp> -<Arrow left>-<End> -<Arrow Down>-<PgDn> -<Return>-Co to the top of the window. One line up.
Co to former window. Backspace.
Go to next window or start calculation. Go to next input line.
Co to next menu.
Value doesn't change/activate input value.
2 Resistance calculation according to GULDHAMMER and
HARVALD.2.1 Introduction
The resistance calculation is based
on the report: Ship resistance,Effect of Form and Principal Dimensions,
(REVISED) by
H.E. Guldhammer and Sv. Aa. Harvald,
1974
Akademisk Forlag COPENHAGEN.
See appendix [4] 2.2 Input menus
There is one input menu divided
over three windows.2.2.1 First window
Length between perpendiculars (m) LPP Length of the construction waterline (m) . LWL
Moulded breadth (m) BR
Midship draft (m) DRAFT
Trim (m)
TRIM
Moulded volume of displacement
(m3) VOLCenter of buoyancy forward op LPP/2 (% of LPP) LCB
Waterplane area coefficient (-) CWP
Midship section coefficient (-) CM
Wetted area hull (if unknown
: SHULL-0) . SHULLShape coefficient aft (-)
Extreme U-Form : CAFT-+0.10
Extreme V-Form : CAFT--0.10
. CAFT
Shape coefficient forward (-)
Extreme U-Form : CFOR--0.10
Extreme V-Form : CFOR-+0.10
. CFOR
Wetted area rudder (m2) SRUD
Wetted area appendages (m2) SAPP
Increase of wave resistance due to appendages (%): Bossings at full ships
: 3-5%
Shaft brackets and shafts at fine ships
: 5-8% CAPP
If the values are
entered then ask for next window
with the key <PgDn> (page down).
2.2.2 Second window
Cross section area bulbous bow (m2)
Bow correction due to Guldh. & Harv. :ABULB
> 0No bow correction
-ABULB 0Bow correction due to Holtr. & Mennen:ABULB
< 0 ABULB Centroid of bulbous bow cross section to keel(m) HBULB Diameter of bow thruster tunnel (m)N bow thrusters :
DBTTDBTT*sqrt(N)
DBTTResistance coefficient of bow thruster tunnel
Thruster in cylindrical part of bow
: CBTT-0.003Thruster at the worst location
: CBTT-0.012 CBTTResistance coefficient due to air,steering,etc.:
Air resistance . . : CAA-0.070Steering resistance : CAA-0.040
Both contributions : CAA-0.110 CAA
If the values are entered then ask for
next window with the key <PgDn> (page down).2.2.3 Third window
Number of ship speeds (max. 25) NV
NR. SHIP SPEED NR. SHIP SPEED
knots knots
etc.
If the input is completed
start calculation with the func-tion key <END>.The program asks: Store data
input? Y(es)/N(o):Yes :
Name of the dataset (without
extension):
Type a name with not more than seven characters. The input data will be saved on disk under the en-tered name with the extension ".GLH".
For the calculation
program, the dataset is copied
into a dataset "REKEN.DAT".No : The input data will not be saved on disk.
For the calculation
program, the input values will
be stored into a dataset "REKEN.DAT".2.3 Menu handling keys
The following keys are used for menu handling: <Home> Go to the top of the window. <Arrow up> - One line up.
<PgUp> - Go to former window.
<Arrow left>- Backspace.
<End> - Go to next window or start calculation.
<Arrow Down>- Go to next
input line. <PgDn> Go to next menu.<Return> -
Value doesn't change/activate
input value.
3 Resistance calculation according to LAP /W.H.
AUF'M KELLER
3.1 IntroductionThe resistance calculation is based
on the report:Extended diagrams for determining the resistance and
required power for single-screw ships,by
W.H. AUF'M KELLER,
International Shipbuilding Progress, Vol. 20 - No. 225 - May 1973
See appendix [5]. 3.2 Input menus
There is one input menu divided
over three windows.3.2.1 First window
Length between perpendiculars (m) LPP Length of the construction waterline (m) . LWL
Moulded breadth (m) BR
Midship draft (m) DRAFT
Moulded volume of displacement (m3) VOL
Center of buoyancy forward of
LPP/2 (% of LPP) LCBMidship section coefficient (-) CM
Wetted area hull (m2) (if unknown
: SHULL-0) SHULLDensity of water:RHO-1025 kg/m3 resistance in N
RHO=1.025 ton/m3 resistance in kN RHO
Resistance coefficient DCFSUM[dcf(i)]
Due to wind :
dcf(1)0.000080
Due to bilge keels : dcf(2)=0.000040
Due to steering : dcf(3)=0.000040
. . DCF
If the values are entered then
ask for next window with the key <PgDn> (page down).3.2.1 Second window
Number of ship speeds (max. 25) NV.
NR.
SHIP SPEED
NR.SHIP SPEED
knots knots
etc.
If the input is completed start calculation with the
func-tion key <END>.The program asks: Store data input? Y(es)/N(o):
- Yes : Name of the dataset (without extension):
Type a name with not more than seven characters.
The input data will be saved
on disk under theen-tered name with the extension ".LAP".
For the calculation program, the dataset is
copied into a dataset "REKEN.DAT".No :
The input data will not be saved
on disk.For the calculation program, the input data
will be stored into a dataset "REKEN.DAT".3.3 Menu handling keys
The following keys are used for
menu handling: <Home> <Arrow up> -<PgUp> <Arrow left>-<End> <Arrow Down>-<PgDn> <Return>Go to the top of the window. One line up.
Go to former window. Backspace.
Go to next window or start calculation. Go to next input line.
Go to next menu.
Value doesn't change/activate
input value.4 Calculation of Wageningen B-Serie Propellers
4.1 Introduction
The propeller calculation is based
on the following reports: Oosterveld M.W.C. and Oossanen P. van,Further computer-analyzed data of the
Wageningen B-Screw Series,Netherlands Ship Model Basin, Publication No. 479.
see appendix [6].
Oosterveld M.W.C. en Oossanen P. van,
Recent developments in marine propeller hydronamics,
Netherlands Ship Model Basin,Int. Jubilee Meeting 40th ann., NSMB 1972,
Wageningen, 1973. See appendix [7].
Oosterveld M.W.C. en Oossanen P. van,
Representation of propeller characteristics
suitable for preliminary ship design studies,International Conference,
Computer Applications of ship yards operation
and shipdesign,
Tokyo, 1973.
See appendix [8].
Theilheimer F. and Starkweather W.,
The fairing of ship lines on a high-speed electronic
com-puter,
D.T.M.B. Report no. 1474, 1961. Nolan T.J.,
Computer Aided Design of developable hull
surfaces, Marine Technology,April 1971. 4.2 Input menus
There is one input menu divided over one or two windows, depen-ding on the input.
In the first design step there is one input window, the known parameters are:
- Diameter propeller. - Ship speed.
-
Thrust calculated by
one of the resistance calculation
pro-grams.
Parameters to be calculated:
- Propeller revolutions. - Blade area ratio.
- Pitch diameter ratio. - Propeller power.
- Propeller efficiency.
For the second design step choose
an engine from a catalogue, delivering the required power.Tune the propeller and engine.
The known parameters are
- Diameter propeller.
- Propeller revolutions.
Propeller power.
Resistance curve calculated by
one of the used resistance calculation programs (SECOND INPUT WINDOW).Parameters to be calculated:
- Blade area ratio. - Pitch diameter ratio. - Ship speed.
- Propeller efficiency.
4.2.1 First window
Number of rev./min
:NS=0-calculate or fill in a value
Diameter in m :
D-0-calculate or fill in
a value
Exp.blade area ratio:AAE-0-calculate
or fill in a valuePitch-diameter ratio:PPD=0-calculate
or fill in a valueNumber of propeller blades:NPB 2<
NPB <-7Shipspeed in knots :
VS=0-calculate or fill in
a value
Relative Rotative Efficiency
RREWake Fraction
PSI
Choice of propulsion param.:1 - fill in propeller thrust
2 - fill in propeller power
3 - fill in propeller torque:
Thrust in kN
IV Propeller power in KW
IV
Propeller Torque in kNm IV
Center propeller shaft to the waterline in m DEPS
Cavitation criterium due to Auf'm
Keller . . KAVMedium IWAT-1 - Sea water , 0 - Fresh water IWAT
Correction parameter:
ICOR=1 Reynoldscorrection,ICOR-2 Correction RN, Roughness and blade thickness
ratio,ICOR-0 No correction
. ICOR
Test output
on screen ?
O - No; 1 - Yes
If the values are entered then ask for next
screen with the key <PgDn> or press <END> to start calculation.
4.2.2 Second window (optional)
NW - POINTS THRUST CURVE
INPUT THRUST CURVE
NW SPEED - (knots) 1 0 0 2 3 etc.
If the input is completed start calculation with the func-tion key <END>.
The program asks: Store data input?
Y(es)/N(o):- Yes : Name of the dataset (without extension):
Type a name with not more than
seven characters.The input data will be saved
on disk under the ente-red name with the extension ".BPR".For the calculation
program, the input data is copied
into a dataset "REKEN.DAT".- No : The input data will not be saved on disk.
For the calculation program, the input values will be stored into a dataset "REKEN.DAT".
4.3 Menu handling keys
The following keys are used for menu handling: <Home> - Go to the top of the window.
<Arrow up>
- One line up.<PgUp> - Go to former window.
<Arrow left>- Backspace.
<End> - Go to next window or
start calculation.
<Arrow Down>- Go to next input
line.<PgDn> - Go to next menu.
<Return> -
Value doesn't change/activate
input value.12
(max. 20) NW
THRUST (KN)
5 Calculation of Ducted Propellers
5.1 Introduction
The propeller calculation is based on the following
reports:M.W.C. Oosterveld,
Wake adapted ducted propellers, Doctoral thesis,
Publicer H.Veenman & Zonen N.V. - Wageningen 1970.
Oosterveld M.W.C. en Oossanen P. van
Recent developments in marine propeller hydronamics,
Netherlands Ship Model Basin,Int. Jubilee Meeting 40th ann., NSMB 1972,
Wageningen, 1973. See appendix [7].
Oosterveld M.W.C. en Oossanen P. van,
Representation of propeller characteristics
suitable for preliminary ship design studies,International Conference,
Computer Applications of ship yards operation and ship
design,
Tokyo, 1973.
See appendix [8]. 5.2 Input menus
There is one input menu divided
over one or two windows, depen-ding on the input.In the first design step there is one input window, the known parameters are:
- Diameter propeller.
- Ship speed.
- Thrust calculated by one of the resistance
calculationpro-grams.
- Bollard pull (optional) - Nozzle type. Parameters to be calculated: - Propeller revolutions. - Pitch-Diameter Ratio. - Propeller power. - Propeller efficiency 13
For the second design step choose an engine from
a catalogue, delivering the required power.Tune the propeller and engine. The known parameters are:
- Diameter propeller. - Propeller revolutions. - Propeller power.
-
Resistance curve calculated by one of the used resistance
calculation programs. (SECOND INPUT WINDOW). Parameters to be calculated:
- Pitch - Diamater Ratio. - Ship speed.
- Propeller efficiency.
5.2.1 First window
Number of rev./min
NS=0-calculate or fill in a value
Diameter in m
D=0-calculate or fill in a value
Pitch-Diameter ratio PPD=0-calculate
or fill in a value Shipspeed in knotsVS=0-calculate or fill in a value
Wake number PSI
Relative Rotative Efficiency
RREChoice of propulsion parameter 1 - Propeller Thrust
2 - Propeller Power
3 - Propeller Torque .
Propeller thrust in kN
IVPropeller power in KW
IVPropeller torque in kNm
IVBollard pull in kN IV(2)
Center propeller shaft to the
waterline in m
DEPS Medium Iwat=1-Seawater, 0-Fresh waterIWAT
Nozzle type
Test output on screen ? 0 - NO, 1 - Yes .
Valid values for the nozzle type are:
36519, 45519, 47019, 47022, 47024, 47037, 510033 and 57519.
If the values are entered
then ask for next window withthe
key <PgDn> or press <END>
to start calculation.5.2.2 Second window (optional)
NW - POINTS THRUST CURVE (max. 20) NW
INPUT THRUST CURVE
NW SPEED THRUST - (knots) (KN) 1 0 0 2 3 etc.
If the input is completed start calculation
with the func-tion key <END>.The program asks: Store data input? Y(es)/N(o):
- Yes : Name of the dataset (without extension):
Type a name with not more than
seven characters.The input data will be saved
on disk under the ente-red name with the extension ".DCT".For the calculation program, the input
data is copied into a dataset "REKEN.DAT".- No :
The input data will not be saved
on disk.For the calculation program, the input values will be stored into a dataset "REKEN.DAT".
5.3 Menu handling keys
The following keys are used for menu handling: <Home> - Go to the top of the window.
<Arrow up>
- One line up.<PgUp> - Go to former window.
<Arrow left>- Backspace.
<End> - Go to next window or start
calculation. <Arrow Down>- Go to next input line.
<PgDn> - Go to next menu.
<Return> - Value doesn't change/activate input value.
6 Hydrostatic programs
6.1 Introduction
The programs are written in Algo1-60 by
Ing. A. Versluis and translated into Fortran 77 by Ing. A.P. de Zwaan.The input description is based
on the following report:Description and use of Algolprograms for
Hydrostaticcalcula-tions, by
Ing. A. Versluis, Report no. 282,
Faculty of Mechanical Engineering and
Maritime Technics, Department of Shiphydromechanics,januari 1971.
For the input description see appendix [9]. 6.2 Input menus
There are four menus
-
A menu for starting the calculation
programs. - A menu for the general input data.-
A menu for the distances between
the succesive calculation
ordinates.Removing or adding calculation
ordinates can be done by changing the number of ordinate intervals.If the entered values are not in accordance to the regula-tions for the input, the
program stops and gives a
message.
Correct the error and the input
program continues.-
A menu for the input of the
hullform cross sections.
The program asks for the number
of points and for the de-sign ordinate number.The design ordinate number is only a control variable which
represents the position of the calculation
ordinate.Removing or adding offsets
can be done by changing thenum-ber of points.
If the entered values are not in accordance to the regula-tions for the input, the program stops and gives a message. Correct the error and the input program continues.
6.2.1 Menu for the general input data
Identification [input check program]: General input data.
Mass density of water
(t/m3)Length between design ordinates (0 and 20) . (m)
Moulded breadth
(m)
Maximum breadth on the waterline
(m)
DRAFT CWL at designord. 0 above baseline
(m)
Trim at design ordinate 20
(m)
Waterline of unloaded ship above the baseline
. (m)Deadrise
(m)
Factor for shell and appendages
( -)
Number of calculation ordinate intervals
( - )
Ranknumber of the midship section
( - )
Distance between DESING ORD. 0 and
CALCULATION ORD 0)(m)If the values are entered then ask
for the next menu with the key <PgDn>.6.2.2 Menu distances between
calculation ordinates Number of ordinate intervalsDISTANCE BETWEEN DISTANCE BETWEEN CALCUL. ORDINATES CALCUL. ORDINATES
0 - 1 15 - 16 ... 1 - 2 ETC. 2 - 3 3 - 4 14 - 15
If the input values are not in accordance to the
regula-tions for the input, the
program stops and gives a
message.
Correct the error and the input program continues. If the values are entered then ask for the
next menu with the key <PgDn>.
6.2.3 Menu for the hullform cross sections
RANKNUMBER ORDINATE
1 DESIGN ORDINATE NUMBER
NUMBER OF POINTS (max. 30)Z - value 1 2 3 4 etc. Y - value
If the entered values are not in accordance to the
regula-tions for the input, the program stops and
gives a message. Correct the error and the input program continues.If the values are entered then ask for the
next screen with the key <PgDn>.RANKNUMBER ORDINATE 2 DESIGN ORDINATE NUMBER NUMBER OF POINTS (max. 30)
Z - value 1 2 3 4 etc. Y - value
If the values are entered then ask for the next screen with the key <PgDn>.
If the input is completed the program asks: do you want to
check the input data
once more? Y(es)/N(o)- Yes :
Co thru all menus again
and check the input data. It's possible to alter the data.
No : The program asks for scaling
factors for transfor-mation of the input data.
For very small ships it is necessary to multiply the input with 10. The input will
be transformed from
m to dm. Readin
the output from the calculationpro-grams dm for m, dm2 for m2 and
dm3 for m3 etc.Scalingfactors for transformation of the input data In length :
XFACT
1In breadth :
YFACT
1In height :
ZFACT
1SCALINGFACTORS OK? Y(es)/N(o):
At the end the program asks
- Did you modified the input data? (Y(es)/N(o)
OR
Save input data [NAME]
The text between []
is the filename given before. When
nottyping a name, the name between [] will be
used.Give a name without extension
Fill in a name with not more than seven characters. The program makes three datasets on disk:
-
A dataset with the filename +
an extension ".INP". -A dataset with the filename +
an extension ".HYD". - A dataset with only the filename itself.In this dataset there are put three zeros. After making a
stability -,trim or a floodable length
calculation one of the zeros will be set to 1, so the program knows that oneof the calculations has already been
made and there is a dataset for:- Stability :
name of the dataset + the extension ".STA"
- Trim :name of the dataset + the extension ".TRI"
- Floodablelength: name of the dataset + the extension ".SCH"
The dataset with extension
".HYD" is calculated from the dataset with the extension ".INP". The ordinate offsetsare calculated with respect to the
mean draft.If the trim is zero then the files with the extensions ".INP" and ".HYD" are equal.
6.3 Menu handling keys
The following keys are used for menu handling: <Home> <Arrow up> -<PgUp> <Arrow left>-<End> <Arrow Down>-<PgDn> <Return>
Co to the top of the
window. One line up.Go to former window. Backspace.
Stop input and go to the end of program. In case of not completed input, this input can be saved and completed afterwards. Go to next input line.
Go to next menu.
Value doesn't change/activate
input value.6.4 Menu for the calculation
programs Check input data and modify.Input control by plotting the body plan
on screen. Displacement calculation.Stability calculation. Trim calculation.
Floodable length curve calculation.
Exit.
Make your choice!
After choosing one of the items with the
cursor the program
starts.
At the end of an operation the program always returs to the
menu above.6.4.1 Check input data and modify
This item is discussed in chapter 6.2.3
6.4.2 Input control by plotting the body plan on screen
The program produces a body plan
on the screen, after a
se-lection is made for the proper screen by means of the
fol-lowing menu:SELECT PROPER SCREEN MODE
After the body plan is produced
on the screen (see fig. 1), it is possible to makea copy on the printer by pressing key
<ScrPrt> or making a plot
on the plotter if one connected.Figure 1. Body plan.
If the program is ready it
turns back to the menu described
in chapter 6.4.20
1). CGA,EGA,VGA,MCGA (320 *
200 PIXELS) 2). OLIVETTI SCREEN (640 * 200 PIXELS)3). EGA,VGA,HERCULES (640
* 350 PIXELS)4). OLIVETTI SCREEN
(640 * 400 PIXELS)6.4.3 Displacement calculation
The program starts to make
a copy of the input data into a
dataset "REKEN.DAT" and makes a call for the displacement calculation program.The program produces the following
text:DISPLACEMENT CALCULATION (20 sec. calc. time)
Date: dd-mm-year Time: hh:min
Filename of output data [PRINTER]:
Pressing the return key the output will be send to the con-nected printer.
Typing "CON" the output will be send to the screen. Typing a name with less
than eight characters the output will
be placed on the disk
under the given name.If the program is ready it turns back to the
menu described in chapter 6.4.
6.4.4 Stability calculation
The following input menu appears on the screen: Additional input for the stability calculation.
Camber 0 - No , 1 - Yes [1]: Yes Trimangle in degrees [0]. 0 Number of depths [6]- 6
Number of angles of
inclination[9]. 9
Stepwidth angles of inclination . . . [10 degr.]: 10
Stability in a sinusoid wave? 0 - No , 1 - Yes [0]: 0
Displacement for the curve of static arms
Matching KG - value . (m3):
(m):
The first 6 values are standard values, it
is possible to change this values. Fill in the the missing
values.
After the input is completed start the
calculation program with the key <END>.
The input will be saved under the
name of the input data
with the extension
".STA".The program starts to copy the input
data + the data with the extension ".STA" into a dataset
"REKEN.DAT" and makes a
call for the stability calculation program.
The program produces the following
text:STABILITY CALCULATION (1.5 min. calc. time)
Date: dd-mm-year Time: hh:min
Filename of output data [PRINTER]:
Pressing the return key the output will be send to the con-nected printer.
Typing "CON" the output will be send to the screen.
Typing a name with less than
eight characters theoutput will
be placed on the disk
under the given name.If the program is ready it turns back to the menu descri-bed in chapter 6.4.
6.4.5 Trim calculation
The following input menu appears on the screen:
Additional input for the
trim calculation.Thickness of the keelplate in m
[0]
Rudder cross section
area in m2[0]
Rudder height in m
[0]
Tonnage (metric - 1000; long tons
- 1016) . . . . [1000]
Distance of Plimsoll line
behind in m (in front of
APP + behind APP -) [0]
Number of measuring points on the stem or on the Plimsoll line forward ATTENTION: AT LEAST 6 MEASURING
POINTS!
If the values
are entered then ask for the next input window with the key <PgDn>.
Data points of the stem or measuring points
of the plimsoll line.
Data points with respect to FPP(in front of FPP x-value+; aft FPP x-value -)
Z - values with respect to the baseline.
Number of data points:
Z - value X - value m ni 0 0 2 0 4 0 etc.
After the input is completed start the
calculation program with the key <END>.
The input will be saved under the
name of the input data
with the extension
".TRI".The program starts to
copy the input data + the data with
the extension ".TRIn into a dataset "REKEN.DAT" and makesa
call for the trim calculation program. The program produces the following text:
TRIM CALCULATION (20
sec. calc. time)Date: dd-mm-year Time: hh:min
Filename of output data [PRINTER]:
Pressing the return key the output will be send to the con-nected printer.
Typing "CON" the output will be send to the screen.
Typing a name with less than
eight characters the output willbe placed on the disk
under the given name.If the program ,is ready, it turns back to the
menu descri-bed in chapter 6.4.
6 4.6 Floodable length
curve calculation
The following input menu appears on the screen: Additional input for floodable length curve. Displacement in m3
Center of buoyancy in length with respect to ord. 10 in m Center of gravity (KG) in height in loading condition
m Number of permeabilities <= 5 IMMERSION-BOUNDARY LINE AT ORDINATE 0: etc. After the input is
completed start the calculation program with the key <END>.
The input will be saved under the name of the input data
with the extension
".SCH".23
le permeability 2e permeability .
etc.
Ask for the next input window with the key
<PgDn>.Distance of immersion
above the baselinein meters (3 INCH BELOW BULKHEAD DECK)
IMMERSION-BOUNDARY LINE
The program starts to copy the input data
+ the data with the extension H.SCH" intoa dataset "REKEN.DAT" and makes a
call for the floodable length curve calculation.The program produces the following
text:FLOODABLE LENGTH CURVE (1.5 min. calc. time)
Date: dd-mm-year Time: hh:min
Filename of output data [PRINTER]:
Pressing the return key the output will be send to the con-nected printer.
Typing "CON" the output will be send to the screen.
Typing a name with less than eight
characters the outputwill be placed on the disk under
the given name.If the program is ready it turns back to the menu descri-bed in chapter 6.4.
6.5 Menu handling keys
The following keys are used for menu handling: <Home>
<Arrow up>
-<PgUp> <Arrow left>-<End> <Arrow Down>-<PgDn> <Return>Go to the top of the window. One line up.
Go to former window. Backspace.
Co to next window or start calculation. Co to next input line.
Go to next menu.
Value doesn't change/activate
input value.NIA
APPENDIX 1.
A STATISTICAL POWER
PREDICTION METHOD byIntroduction
In a previous paper, [I], a numerical representation
of resistance properties and propulsion factors was presented that could be used for statistical
perfor-mance prediction of ships. After more than a year of
experience several fields
for improvement of the
derived prediction method can be indicated:
the formula for the wave-making resistance does not include the influence of a bulbous bow; this implies that especially the resistance of ships with large
bul-bous bows is over-estimated by the original for-mula.
the resistance of fast naval ships appeared not to be
represented accurately enough by the statistical
formula; more in particular the wave-making
resist-ance of ships with a large waterplane-area
coef-ficient is over-estimated by the previous formula.
it appeared that the accuracy of the formula for the thrust deduction fraction for slender single-screw
ships is insufficient.
the wake fraction and the model-ship correlation
allowance
are not properly represented by the
formulas for full ships at ballast diaught.
Focussed on the above-mentioned points for
im-provement of the prediction method a new statistical analysis was made. The presented revised formulas for statistical power prediction are based on more ex-perimental results than the original equations given in
(1].
Re-analysis of resistance data
The total resistance of a ship is generally subdivided
into components of different origin. In the numerical
representation of the total resistance the following
components were considered: equivalent flat plate resistance;
- form resistance of the hull;
- viscous drag of appendages;
- wave-making and wave-breaking resistance;
resistance of a (not fully immersed) bulbous bow;
- model-ship correlation allowance.
In the present statistical study each componentwas expressed as a function of the speed and hull form
parameters. The numerical constants in the regression
equations were obtained from random model test data.
*) Netherlands Ship Model Basin, Wageningen. The Netherlands.
A STATISTICAL POWER PREDICTION METHOD by
J. Holtrop and G.G.J. Mennen *
The first, second arid third mentioned component
were described using the form-factor concept:
Rv = 'hp V2 CF (l+k)Stot
in which p is the mass density of the water, V the
speed, CF the coefficient of frictional resistance,
(l+k) the form factor and Stnt the projected wettedsurface including that of the appendages.
The coefficient of frictional resistance was
deter-mined using the ITTC-1957 formula: 0.075
C =
F (logRn 2)2
with the Reynolds number. Rn based on the waterline length L. The form factor (1 +k). can be divided into
the form factor of the single hull (l+ki ) and a
con-tribution of the appendage resistance (l+k2): l+k = l+ki+ I (l+k2)(1+k1) I Sapp /Stot
In Table 1 tentative values of (l+k2) are given.
Table 1
Appendage factor 1 + k2
The form factor for the bare hull (1+1c1 ) can be ap-proximated by the formula:
l+ki = 0.93+(T/L)0.22284(B/LR )0.92497
(0.95 Ce )-0.521448( 1 Cp +0.0225 1 cb)°.69°6
In this formula T is the average moulded draught,
L is the length on the waterline, Cp is the prismatic coefficient and kb is the longitudinal position of thi centre of buoyancy forward of 0.5L as a percentage of the waterline length L. LR is the length of the run
and is approximated by:
= 1 Cp +0.06Cp Icb/(4Cp 1 )
253
Appendage configuration 1 + k2
rudder - single screw 1.1 - 1.5
rudders - twin screw 2.2
rudders + shaft brackets - twin screw 2.7 rudders + shaft bossings - twin screw 2.4
stabilizer fins 2.8
bilge keels 1.4
254
The projected wetted surface of the bare hull was
correlated with the data of 191 ship models. The
following statistical formula involving a standard deviation of a = 1.8 per cent was deduced:S = L(2T+B)NrC;(0.453+0.4425CB -0.2862Cm +
-0.003467B/T+0.3696Cwp )+2.38ABT /CB
In this formula Cm is the midship-section coefficient. L the, length of the waterline, T the average moulded
draught, B the breadth, CB the block coefficient,
Cwp the waterplane coefficient and ABT is the
trans-verse sectional area of the bulb.
The wave-making and wave-breaking resistance
com-ponents were described using the following represen-tation for the dependency on the speed:
Rw
= ci c2exp I m Fd. +m2 cos(XF.-2 )
In this equation, in which Rw /A is the Froude-num-ber dependent resistance per unit displacement and F.
the Froude number based on the waterline length.
The coefficients cl, c2, m1, d, m2 and X are functions
of the hull form.
The coefficient X can be determined from: X = 1.446Cp -0.03L/B
From a regression analysis using the
above-mention-ed equation for the wave-making resistance with the
exponent
d = -0.9
the following formulas for the coefficients c1, C2, mi
and m2 were derived:
= 2223105ovw3-78613(T/B)1.07961(90-0.5 0-137565
C2 = exp(-1.89VT3' )
m = 0.0140407L/T-1.75254V1/3/ L-4.79323B/L+ -8.07981 C, +13.8673q -6.984388CP m2 = -1.69385C; exp (-0.1/F! )
The coefficient c3, that accounts for the reduction of the wave reAistance due to the action of a bulbous
bow, is defined as:
C3 = 0.56Aid / I BT(0.56NrA7T+T1, -hB -0.25') I
In the above given formulas 0.5a is the angle of the waterline at the bow in degrees with reference to the
centre plane neglecting the local shape at the stem, V is the displacement volume, ABT is the transverse area of
the bulbous bow, hi/ is the position of the centre of area ABT above the base and T,, is the draught on the
forward perpendicular. The half angle of entrance
can be approximated by:
0.Sa = 125.67B/L-162.25q+234.32q,+
6.8(TA -Try
+0.155087(lob+
T
With respect to the resistance of a bulbous bow
vvhich is close to the water surface a tentative fonnuli
was deduced using the results of only a few model
tests. From inspection of these test results it was
con-eluded that the relation to the speed could be rem-.
sented well by:
RB =FL/(1+Fn2i)
In which Fro is the Froude number based on the
im-mersion:
Fni = V/Vg i+0.15V2
with
i = TF -hB -0.25/74./ ./.
In the definitions above: speed
acceleration due to gravity draught forward
position of centre of area ABT above base
transverse area of the bulb at the position where the still water plane intersects the
stem.
As a measure for the emergence of the bulbous bow
from the still water surface the coefficient pi) was
introduced with:
pB = /(TF -1.5hB )
It appeared that the resistance of a bulbous bow
could be described fairly well according to:
RB = 0.11 exp ( -3 p-B2) F.3/ A p g/( 1+Fiii )
With respect to the model-ship correlation resistance RA it was observed that the correlation allowance CA with
CA = RA '( 1/2p V2)
Stot-for full ships in ballast condition is about 0.0001 high-er than at the loaded draught.
A possible explanation for this difference can be found in the interaction of the wake of the breaking
bow wave with the relatively thick boundary layer on the hull on model scale.
According to this explanation the difference in CA
value will be present only if in fully loaded condition
wave breaking is absent, whereas it is supposed to
occur at the ballast draught. Based on the results of
108 measurements made during the speed trials of 54
new ships the following formula for CA having a
standard deviation of o = 0.0002 was deduced:
V =
g =
TF
hB
Y°
CA 0.006(Ls +100 0.00205 +
+ 0.003NiLs /Lmcic2
(0.04c4)
with c4 = TF /Ls if TF /Ls.< 0.04 or
c4 =0.04 if TF LB > 0.04.
In this formula Ls is the length on the waterline ofthe
ship, Lm the similar value for the ship model, CB the
block coefficient and TF the draught fonvard. The
coefficient c2 accounts for the influence of a bulbous bow on the wave-breaking resistance. For calculating full-size resistance values for ideal trial conditions the above given formula can be used employing a typical
model length of Lm = 7.5 metres.
Application of the afore-mentioned statistical
re-sistance formulas showed a standard deviation of 5.9
per cent of the total model resistance values.
3. Statistical data for propulsion factors
New formulas for the thrust deduction fraction, the
effective wake fraction and the relative rotative
ef-ficiency were derived for single-screw ships. The thrust deduction fraction, defined by
t= 1R/T,
in which R is the total resistance and T the propeller
thrust, can be approximated by:
t = 0.001979L/(BB Cp )+1.0585B/L-0.00524+
0.1418D2/(BT)
In this formula B is the moulded breadth, T the aver-age moulded draught, D the propeller diameter and
Cp the prismatic coefficient.
For the effective wake fraction based on thrust
identity the following formula was derived:
BSCv 10.0661875 1.21756Cv
w DTA TA +
Cp ))+
+ 0.24558/B
L(I Ce)
_
0 097260.95Ce
+0 114340.95CBIn this formula Cv is the
viscous resistancecoef-ficient, determined from: Cv = (l+k)CF + CA
S is the total wetted surface, TA is the draught aft and D is the propeller diameter. The above-mentioned for-mula has been derived from the results of model
ex-periments and speed trials. The full-size wake
frac-tions were determined using the following calculation
procedure:
a. The measured trial speed, rotation rate and shaft
power were corrected for ideal trials conditions: - no wind, waves and swell
- deep sea water of 15 degrees centigrade and a
mass density of 1025 kg/m3
- a clean hull and propeller
The open water torque coefficient was determined
from these values assuming a shafting efficiency of us = 0.99 and using the relative-rotative efficiency
from the model test.
The open-water characteristics of the propeller
were determined from the results of the open-water test with the model propeller by correcting for the proper Reynolds number and the average full-size blade roughness according to the method proposed
by Lindgren, [2].
The effective wake fraction then followed from:
w = 1JnD/V
in which J is the advance coefficient, n the rotation
rate of the propeller and V the sp'eed.
The relative-rotative efficiency can be approx-imated by
nR = 0.9922-0.05908AB /A0 +0.07424CpA
In this formula AB /A0 is the expanded blade area
ratio and CpA is the prismatic coefficient of the
afterbody. CpA can be approximated by:
CpA =C0.0225
0.0225 Icb
With respect to twin-screw ships only tentative
formulas are presented:
w = 0.3095 CB + 1 OCv CB 0.23D/NFITT
t = 0.325 CB
0.1885DWT3T-nR = 0.9737+0.111 (Cp 0.0225 lcb) 0.06325P/D
In these formulas Cv is the viscous resistance
coef-ficient, D is the propeller diameter and P/D is the
pitch-diameter ratio.
4. Application in prelirninary ship design
The numerical description of the resistance com-ponents and propulsion factors can be used for the determination of the propulsive power of ships in the preliminary design stage. In this stage the efficiency of the propeller has to beestimated. To this purposea propeller can be designed using the characteristics of
e.g. the B-series propellers. Polynomialsfor the thrust
and torque coefficient of thisextensive propeller series are given in [31. The calculation procedure for deter-mining the required power proceeds along the
follow-ing lines:
-
for the design speed the
resistance components
described in Section 2 are determined.
256
for a practical range of propeller diameters the thrust deduction and the effective wake fraction
are calculated.
the required thrust is determined from the resistance
and the thrust deduction.
the blade area ratio is estimated.
for a practical range of rotation rates the pitch
ratio as well as open-water thrust and torque
coef-ficient are determined from the polynomials given in [3]
the scale effects on the propeller characteristics
are determined from the method described in [2]. the shaft power is calculated for each combination
of propeller diameter and rotation rate using the
statistical formula for the relative-rotative efficiency and a shafting efficiency of ns = 0.99.
that combination of rotation rate and propeller
diameter is chosen that yields the lowest power;
further optimization of the propeller diameter and rotation rate, employing e.g. the embedded search
technique can then be carried out.
5. Final remarks
The presented formulas for the resistance and
pro-pulsion properties constitute an appreciable
improve-ment with respect to the previously given form
in [1] . Especially, the incorporation of the Mu
of a bulbous bow in the numerical description of
resistance is considered important.
Apart from the application in preliminary
design, where the presented method can be used for parameter studies,. the method is also of importan for the determination of the required propulsivepow
from model experiments. The given formulas for model-ship correlation allowance and the effee wake, from which the wake scale effect can be easily
deduced, can be employed in the extrapolation fro)
model test results to full-size values.
References
Holtrop, J., "A statistical analysis of performance test
results", International Shipbuilding Progress, Vol. 24, Na, 270, February 1977.
Lindgren, H., "Ship model correlation based on theoretical considerations", 13th International Towing Tank Conference, Berlin and Hamburg, 1972.
Oosterveld, M.W.C. and Oossanen, P. van, "Representation
of propeller characteristics suitable for preliminary ship design studies", International Conference on Computer
APPENDIX 2.
AN APPROXIMATE POWER PREDICTION METHOD
by166
Introduction
In a recent publication [1] a statistical method was presented for the determination of the required
pro-pulsive power at the initial design stage of a ship. This
method was developed through a regression analysis
of random model experiments and full-scale data,
available at the Netherlands Ship Model Basin. Because
the accuracy of the method was reported to be insuf-ficient when unconventional combinations of main
parameters were used, an attempt was made to extend the method by adjusting the original numerical predic-tion model to test data obtained in some specific cases.
This adaptation of the method has resulted into a set of prediction formulae with a wider range of applica-tion. Nevertheless, it should be noticed that the given
modifications have a tentative character only, because
the adjustments are based on a small number of ex-periments. In any case, the application is limited to hull forms resembling the average ship described by
the main dimensions and form coefficients used in the method.
The extension of the method was focussed on
im-proving the power prediction of high-block ships with low L/B-ratios and of slender naval ships with a
com-plex appendage arrangement and immersed transom
sterns.
Some parts of this study were carried out in the
scope of the NSMB Co-operative Research programme.
The adaptation of the method to naval ships was
carried out in a research study for the Royal
Nether-lands Navy. Permission to publish results of these
studies is gratefully admowledged.
Resistance prediction
The total resistance of a ship has been subdivided into:
Rtntat RF(1 + ) + RApp+ Rw+ RB+ RTR+
RA
where:
RF frictional resistance according to the
ITTC-1957 friction formula
l+ki form factor describing the viscous resistance
of the hull form in relation to RF RApp resistance of appendages
Rw wave-making and wave-brealcing resistance RB additional pressure resistance of bulbous bow
near the water surface
Netherlands Ship Model Basin, (Marin), Wageningen, The Netherland&
AN APPROXIMATE POWER PREDICTION METHOD by
J. Holtrop* and G.G.J. Mennen*
RTR additional pressure resistance of immersed
transom stern
RA model-ship correlation resistance.
For the form factor of the hull the prediction
for-mula:
1 + k1 = c13 {0.93 + c12(BILR )0.92497
(0.95 y-0321448
( 1 Cp + 0.0225 /cb)13.6906 I
can be used.
In this formula Cp is the prismatic coefficient based
on the waterline length L and lcb is the longitudinal position of the centre of buoyancy forward of 0.5L as a percentage of L. In the form-factor formula LB is a parameter reflecting the length of the run according
to:
LB/L= 1 Cp + 0.06 Cpkb1(4Cp 1)
The coefficient c12 is defined as:
c12 = (I-V.2228446 when TIL> 0.05
C12 = 48.20( T/L 0.02)2'078 + 0.479948
when 0.02 < T/L< 0.05
C12 = 0'479948 when TIL< 0.02
In this formula T is the average moulded draught.
The coefficient c13 accounts for the specific shape of
the afterbody and is related to the coefficient Cstern ac-cording to:
c13 = 1 + 0.003 Cstern
For the coefficient Cstern the following tentative
guidelines are given:
Afterbody form Cstern
V-shaped sections I 0
Normal section shape U-shaped sections with
Hogner stern + 10
The wetted area of the hull can be approximated
well by:
S = L(2T + B)NrC7f(0.453 + 0.4425 CB+
0.2862 CM 0.003467 BIT + 0.3696 Cwp) +
+ 2.38 ABT/CB .
In this formula Cm is the midship section
waterline length L, Cwp is the waterplane area coef-ficient and A87 is the transverse sectional area of the bulb at the position where thestill-water surface
inter-sects the stem.
The appendage resistance can be determined from: RApp = 0.5 pV2SApp(l+k2)c7CF
where p is the water density, V thespeed of the ship, SApp the wetted area of the appendages, 1 + k2 the appendage resistance factor and CF the coefficient of
frictional resistance of the ship according to the IT1'C-1957 formula.
In the Table below
tentative 1 + k2 values aregiven for streamlined flow-oriented appendages. These
values were obtained from resistance tests with bare and appended ship models. In several of these tests turbulence stimulators were present at the leading
edges to induce turbulent flow over the appendages. Approximate 1 + k2 values
with:
= 2223105 CP8613 (m)1.07961 (90 id-1.37565
C7 = 0.229577 (B1L )O'33333 when B/L < 0.11
The equivalent 1 + k2 value for a combination of
appendages is determined from:
E(1 + k2 )SApp
(1 +k2)e
-q ESApp
The appendage resistance can be increased by the
resistance of bow thruster tunnel openings according
to:
P V2 Ird2 CBTO
where d is the tunnel diameter.
The coefficient CBT0 ranges from 0.003 to 0.012. For openings in the cylindrical part of a bulbous bow the lower figures should be used
The wave resistance isdetermined from:
Rw = cic2csV pgexp{m 1P13 + m2 cos(XF;2))
cis= - 1.69385 + (L/7 1/3- 8.0)/2.36
d= -0.9
The half angle of entrance is is the angle of the waterline at the bow in degrees with reference to the
centre plane but neglecting the local shape at the stem. If is. is unknown, use can be made of the following formula:
-= 1 + 89 exp (L0)0.80856 (I cwp)0.30484
(1 - CF - 0.0225 Icb)(16367(LR /B)°34574
(100 VW)0.16302 ). 6.<
This formula, obtained by regression analysis ofover
200 hull shapes, yieldsis values between 1° and 90°.
The original equation in [1] sometimes resulted in
negative iE values for exceptional combinations of
hull-form parameters.
The coefficient that determines the influence of the
bulbous bow on the wave resistance is defined as: c3 = 0.56 AM. I {BT (0 .31 ViTi; + T
ki)}
167
rudder behind skeg
1.5- 2.0
rudder behind stern 1.3 - 1.5.) twin-screw balance rudders 2.8
shaft brackets 3.0 skeg 1.5 - 2.0 strut bossings 3.0 hull bossings 2.0 shafts 2.0 - 4.0 stabilizer fins 2.8 dome 2.7 bilge keels 1.4 C7 = BIL when 0.11 <B/L< 0.25 C7 = 0.5 - 0.0625 LIB when BIL> 0.25 C2 = exp(- 1.89 Vc3)
Cs = 1 - 0.8 A TART Cm)
In these expressions c2 is a parameter which accounts
for the reduction of thewave resistance due to the
ac-fluence of a transom stern on the wave resistance. In
tion of a bulbous bow. Similarly, cs expresses the
in-the expression AT represents in-the immersed part of
the transverse area of the transom at zero speed.
In this figure the transverse area of wedges placed at
the transom chine should be included.
In the formula for the
wave resistance, Fn is theFroude number based on the waterline length L. The
other parameters can be determined from:
X = 1.446 Cp - 0.03 LIB when LIB < 12 X = 1.446 Cp - 0.36 when LIB> 12 m1 = 0.0140407 LIT - 1.75254 I/3/L + - 4.79323 BIL - ci6 c16= 8.07981 Cp - 13.8673 C3 + 6.984388 when Cp < 0.80 CI6 1.73014 - 0.7067 C/1 when Cp > 0.80
1722 = CIS Ci? exp(- 0.1 F;2
The coefficient c15 is equal to - 1.69385 for L3/7 <
512, whereas cis= 0.0 for L3/7 > 1727.
For values of 512 < L3/7 <1727, c15 is determined
qz:17
168
where hB is the position of the centre of the
trans-verse area ABT above the keel line and TF is the
for-ward draught of the ship.
The additional resistance due to the presence of a
bulbous bow near the surface is determined from:
RB= 0.11 exp(- 3 Pi 2) F n3 pg1(1+ FL) where the coefficient PB is a measure for the emer-gence of the bow and Fni is the Froude number based
on the immersion:
Pß = 0.56 ./74;271(T - 1.5 hB)
and
= V ag(T - hB -0.25 Nai; ) + 0.15 V2
In a similar way the additional pressure resistance
due to the immersed transom can be determined:
RTR 0.5PV2ATC6
The coefficient c6 has been related to the Froude
number based on the transom immersion:
C6 = 0.2(1 - 0.2 Par) when FnT < 5
or
c6=0
when Fer 5FnT has been defined as:
FnT = VA/2 ,gA 7.1(B +B Cwp)
In this defmition Cwp is the waterplane area
coeffi-cient.
The model-ship correlation resistance RA with
RA =1/2. pV2S CA
is supposed to describe primarily the effect of the hull roughness and the still-air resistance. From an analysis of results of speed trials, which have been corrected to
ideal trial conditions, the following formula for the
correlation allowance coefficient CA was found:
CA 0.006(L + 100)-0.16 0.00205 + + 0.003N //Tr-7.5 c2(0.04 - c4) with c4 = TF/L when T p IL 0.04 Or C4 = 0'04 when TFIL> 0.04
In addition, CA might be increased to calculate e.g.
the effect of a larger hull roughness than standard. To this end the ITTC-1978 formulation can be used from
which the increase of CA can be derived for roughness values higher than the standard figure of ks = 150 Atm (mean apparent amplitude):
increase CA =(0.105 k,113 - 0.005579)/L3
In these formulae L and ks, are given in metres.
3. Prediction of propulsion factors
The statistical prediction formulae for estimating the effective wake fraction, the thrust deduction
frac-tion and the relative-rotative efficiency as presented in [1] could be improved on several points.
For single-screw ships with a conventional stern
ar-rangement the following adapted formula for the wake fraction can be used:
Cy +
w-c9
Cvr
A(0.0661875+ l.21756c1111 (1-Cp1))
+0.24558,1
B 0.09726 0.11434 L(1 - Cp1)0.95-Ce
0.95 -CB + 0.75 Cstem Cy + 0.002 Cstem-The coefficient c9 depends on a coefficient c8 defmed
as: c8 = BSALDTA) or c8= S(7 BITA -25)1(LD(BITA - 3)) when BITA > 5 C9 = C8 when c8< 28 Or = 32 - 16/(c8 - 24) when c8 > 28 cii = /D when TA < 2 Or c11 = 0.0833333( TA /D)3 + 1.33333 when TA > 2
In the formula for the wake fraction, Cy is the
vis-cous resistance coefficient with Cy = (1 + k) CF + CA. Further:
Cp1 = 1.45 Cp - 0.315 - 0.0225 lcb
In a similar manner the following approximate
for-mula for the thrust deduction for single-screw ships
with a conventional stern can be applied: t = 0.001979 LAB - BCp1)+ 1.0585 c10 +
- 0.00524 - 0.1418 D2 l(BT)+ 0.0015 Cs
The coefficient clo is defmed as:
C10 =BIL when LIB> 5.2
Or
c10 = 0.25 - 0.003328402/(B/L - 0.134615385)
when LIB < 5.2
The relative-rotative efficiency can be predicted
