Evaluacion Metodo Van Oortmerssen
description
Transcript of Evaluacion Metodo Van Oortmerssen
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
918
Evaluation of methods for estimating power to the most
common form of hulls in the Amazon
Hito Braga de Moraes Federal University of Par - Brazil
Philip Alan Wilson University of Southampton - United Kingdom
ABSTRACT
The Amazon region has had only a few studies in the field of naval architecture. This
paper will explore the design of specific craft suitable for this environmentally
sensitive region. The design will require verification and validation of the
computational methods used to assess the hydrodynamics of the typical vessels
commonly used in the Amazon region.
This research presents estimation methods for power boats, where one seeks to
compare several statistical methods, based on systematic series and methods which
use finite element theory with the results obtained from experiments performed in the
towing tank. For the validation of the power estimate it is necessary to compare the
results generated by these methodologies with the results obtained in tests with
scaled models in a towing tank.
An identification process was used to determine three typical types of regional
powered vessels on the Amazon. The effective power was then analysed for these
vessels. After selecting the type of hull, ship models were constructed for testing in
the towing tank. Comparisons are then made between theory and scaled models.
Nomenclature
B Ship beam (m.)
CB Block coefficient
Cf Coefficient of frictional resistance
CM Mid ship area coefficient
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
919
Cp Prismatic coefficient
Fn Froude number
Fn Froude number based on volume
L Ship length (m.)
LD Displacement length (m.)
LBP Length of ship between perpendiculars (m)
Lwl Length on waterline (m)
LCB Longitudinal centre of buoyancy (m.)
PE Effective power (kW)
RR Residual resistance coefficient
S Wetted surface area (m2)
T Ship draft (m.)
V Ship velocity (m. s-1)
Vk Ship speed in knots
D Ship displacement (tonnes)
a Angle of entrance (degs.)
1 INTRODUCTION
Passenger transport in the Amazon region has used, mostly, wooden craft built by
virtue of being the most abundant material in the region and easy maintenance and
replacement. The traditional construction technique that is used is without much
technical guidance to produce the most suitable hull shape and the power required
for the propulsion of such vessels. This practice leads to inappropriate projects and
very high operating costs due to lack of technical information about the power
required for the desired speed.
2 TYPES AND FORMS OF HULLS USED IN THE AMAZON
From a study of the actual craft used in the area three models of typical boats that
are used within the Amazon region, were used for testing in towing tank experiments.
After searching for the typical forms of hull in the Amazon region, the identification of
lines plan of the three most common forms of boats in the Amazon region (small,
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
920
medium and large) were produced, with the goal of finding the estimates of
resistance. The range of these three boats is 11m to 28.8m. This was performed by
measuring resistance in the towing tank and also the equivalent propulsive
parameters by testing self-propelled models small-scale models were constructed of
the three types of boats for tests in towing tank.
The tests consisted of towing the model along the tank, using the dynamometer on
the support carriage, to measure the resistance force for each forward speed.
During each run, measurements were made of the forward speed and towing force,
the angle of trim and the sinkage of each model. The towing tests were
conducted over a range of scale speeds centred on the design speed giving a
range, corresponding to a full range of 4 to 15 knots. The details of the test tank used
are found in Table 1.
Table 1: Main dimensions of the towing tank
main characteristics
Length m 280.00
Width m 6.60
Water depth m 4.50
Maximum carriage
velocity
m/s 3.50
a) SMALL VESSEL
Table 2: Small Vessel
Base data Coefficients
Length 11 m. Cp 0.70
Beam 2.43 m. Cb 0.52
Draught 0.65 m.
Displacement 9 tonnes - -
Wetted Area 28.6 m2 - -
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
921
To make the model of the hull SMALL it was necessary to use the lines plan of model
illustrated in Figure 1. The actual scale of the model is 15.0.
Figure 1: Lines plan SMALL VESSEL
Figure 2 shows the scale model produced and in Figure 3 the software
rendering of the finite elements is shown.
Figure 2: Small-scale model of the SMALL VESSEL
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
922
Figure 3: SMALL VESSEL modelled in software
b) MEDIUM VESSEL:
Table 3: Medium Vessel
Base data Coefficients
Length 20.3 m. Cp 0.71
Beam 4.8 m. Cb 0.71
Draught 1.2 m.
Displacement 82.80 tonnes - -
Wetted Area 127.4 m2
- -
To produce the model of the ship hull MEDIUM was necessary to use the lines plan
of small-scale model illustrated in Figure 4. As with the other ship model Figure 5
illustrates the actual scale model with a scale of 15.0. Figure 6 is the software
rendered model of the finite elements.
Figure 4: Lines plan MEDIUM VESSEL
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
923
Figure 5: Small-scale model of the MEDIUM VESSEL
Figure 6: MEDIUM VESSEL modelled in software
c) LARGE VESSEL:
Table 4: Large vessel
Base data Coefficient
s
Length 28.8 m. Cp 0,71
Beam 7.5 m. Cb 0,57
Draught 1.9 m. - -
Displacement 234.69 tonnes - -
Wetted Area 250.12 m2 - -
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
924
To produce the model of the ship hull LARGE was necessary to use the lines plan
illustrated in the following Figure 7. The scale used is 15.0.The scale model used in
the towing tank tests is shown in Figure 8 and the equivalent rendered model used in
FEA software is shown in Figure 9.
Figure 7: Lines plan LARGE VESSEL
Figure 8: Small-scale model of the LARGE VESSEL
Figure 9: LARGE VESSEL modelled in software
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
925
3 METHODS FOR ESTIMATING POWER
There are several methods adopted to estimate the effective power of each ship that
is presented below.
3.1 Van Oortmerssen: Small Ships
Van Oortmerssen [10] developed regression equations for estimating the resistance
of small ships such as tugs, fishing boats, stern trawlers and pilot boats, broadly in
the full scale length range 15 m to 75 m. The objective was to provide equations that
would be accurate enough for design purposes. The analysis was based on 970 data
points from 93 ship models that had been tested at The Netherlands Ship Model
Basin (NSMB) (now Maritime Research Institute of the Netherlands [MARIN]) in the
1960s.
Approximate limits of the data (extracted from the diagrams) are as follows:
Froude number, Fn = 0.2 0.5
L/ B = 3.4 6.2
LCB: - 4.4%L to + 1.6%L
: 15- 35.
Where is the half-angle of entrance of the waterline at the bow. If is not known,
an approximation is =12.0 CB - 50 (0.5
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
926
The residuary resistance was derived using the ITTC1957 1ine for Cp. The
components of the equation for residuary resistance ratio RR / are as follows:
2 2 2
2
/9 21 2 3
24
sin
cos
n n n
n
n
n
m F mF mFR
mF
RC e C e C e F
C e F
- - -
-
- - - -
- -
= + +D
+
(2)
Where, m = 0.1434 CP -2.1976 (3)
c = {di,0 + di,1 . LCB + di,2 . LCB2 + di,3 . Cp + di,4 CP + di,5 . (LD/ B) + di,6 . (LD/ B)
2 + di,7
. CWL + di,8 . CWL2 + di,9 . (B/T) + di,l0 . (B/T)
2 + di,11 . CM} x 10 -3, (4)
where, LCB forward of 0.5 L as a percentage of L and the coefficients di are given
in Table 5.
Table 5: Van Oortmerssen [10]: Small ship resistance regression coefficients
i = 1 2 3 4
di,0 79, 32134 6714,88397 -
908,44371
3012,14549
di,1 -0,09287 19,83 2,52704 2,71437
di,2 -0,00209 2,66997 -0,35794 0,25521
di,3 -
246,45896
-19662,024 755,1866 -9198,8084
di,4 187,13664 14099,904 -48,93952 6886,60416
di,5 -1,42893 137,33613 9,86873 -159,92694
di,6 0,11898 -13,36938 -0,77652 16,23621
di,7 0,15727 -4,49852 3,7902 -0,82014
di,8 -0,00064 0,021 -0,01879 0,00225
di,9 -2,52862 216,44923 -9,24399 236,3797
di,10 0,50619 -35,07602 1,28571 -44,1782
di,11 1,62851 -128,72535 250,6491 207,2558
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
927
Table 6: Trial allowances for CF
Allowances for CF
Roughness, all-
welded bulls
0.00035
Steering resistance 0.00004
Bilge keel resistance 0.00004
Air resistance 0.00008
The residuary resistance is calculated as:
(5)
Cf is derived using the ITTC formula.
Cf= 0.075/(log10 Re 2 )2 (6)
Cf allowances for trial conditions are again given in Table 5
Friction resistance is then derived as:
(7)
S can be calculated from:
S = 3.223V2/3 + 0.5402LD V1/3 (8)
3.2 WUMTIA: Small Craft: Round Bilge Series
A regression analysis was carried out on chine and round-bilge hull forms which had
been tested by WUMTIA at the University of Southampton. Over 600 hull forms had
been tested by WUMTIA since 1968, including both hard chined and round-bilge hull
forms representing vessels ranging typically from 10 m to 70 m.
Thirty test models of round-bilge generic form were used in the regression analysis.
Tests at different displacements were also included leading to a total of 47 sets of
round-bilge resistance data. The data were all taken from hull forms that had been
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
928
optimised for their running trim characteristics at realistic operating speeds and
include, the effects of change in wetted are a with speed.
The analyses covered the speed range, as follows: The volume Froude number Fn
in the range 0.50 - 2.75, or approximate length Froude number range Fn = 0.25 - 1.2,
where
1/3n
VF
g=
, nV
FgL
= , and nF = 0.5
1/3( )nL
F
It is noted that for the round-bilge hulls there are few data between L/B > 5.5 - 6.5.
Above Fn=1.5, the upper limit of L/B is 5.5, and it is recommended that the data for
L/B > 5.5 be restricted to speeds < Fn = 1.5.
The data are presented in terms of a C-Factor (CFAC) which was developed by small
craft designers for the prediction of power at an early design stage
E
FACPL
VC
21266.30
D= (9)
Where the constant 30.1266 was introduced to conserve the value of CFAC, which
was originally based on imperial units. Above a Fn of about 1.0, CFAC lies typically
between about 50 and 70. Thus by rearranging equation 9 we get the effective
power,
FAC
KE
CL
VP
2
18.453 D= (10)
Where PE is in kW, is in tonnes, VK is in knots and L is in metres. The predictions
for CFAC (round-bilge hulls) are presented as regression equations.
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
929
CFAC = ao + al (L/1/3) + a2 L/B + a3 (S/L
2)1/2 + a4 (L/1/3)2 + a5 (L/B)
2 + a6 (S/L2) + a7 (L/
1/3)3
+ a8 (L/B)3 + a9 (S/L
2)3/2 (11)
The wetted area S for the round-bilge can be estimated using Equation (12).
S = 0.355636() + 5.75893(L) - 3.17064(B) (12)
The regression coefficients ao to a9 in Equations (11) are given in Tables 6.
It should be noted that these regression equations (CFAC) tend to give slightly
pessimistic predictions of power. As a result of advances in scaling techniques and
the inclusion of extra model data in an updated analysis, it is recommended that the
original predictions for the round bilge hulls be reduced on average by 4%.
Table 7. WUMTIA Resistance regression coefficients for C-factor, round bilge
PARAMETER Frv 0,5 0,75 1 1,25 1,5
a0 1136,829 -4276,159 -921,0902 -449,8701 -605,9794
L/Vol1/3 a1 -54,50337 859,2251 460,6681 243,5577 3,073361
L/B a2 -261,8232 98,15745 2,604913 59,9026 -32,77933
(S/L2)0,5 a3 -2695,885 16369,41 737,8893 -223,2636 4097,999
(L/Vol1/3)2 a4 5,365086 -153,5496 -75,42524 -40,36861 -1,682758
(L/B)2 a5 59,31649 -24,77183 -0,706952 -12,58654 6,486023
(S/L2) a6 5300,271 -32787,07 -2325,398 7,616481 -7823,835
(L/Vol1/3)3 a7 -0,136343 9,031855 4,114508 2,222081 0,200794
(L/B)3 a8 -4,207338 1,970939 0,112712 0,901679 -0,341222
(S/L2)3/2 a9 -3592,034 21484,47 2095,625 274,9351 4961,028
Table 7 . Continuation
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
930
PARAMETER Frv 1,75 2 2,25 2,5 2,75
a0 -437,3817 351,1909 813,1732 -622,9426 -1219,095
L/Vol1/3 a1 40,51505 -183,7483 -194,1047 200,5628 346,1326
L/B a2 -87,85154 -101,2289 -63,92188 -138,7268 -139,0729
(S/L2)0,5 a3 3101,983 956,9388 -1884,341 2745,177 4659,579
(L/Vol1/3)2 a4 -4,308722 35,62357 36,56844 -31,93601 -56,785
(L/B)2 a5 20,96359 25,14769 17,01779 36,50832 36,71361
(S/L2) a6 -6339,599 -2061,44 3417,534 -5770,126 -9650,592
(L/Vol1/3)3 a7 0,104035 -2,254183 -2,264704 1,682685 3,096224
(L/B)3 a8 -1,586765 -2,004468 -1,429349 -3,082187 -3,124286
(S/L2)3/2 a9 4302,659 1473,702 -2022,774 4046,07 6655,716
3.3 NPL Series
This systematic series of round-bilge semi-displacement hull forms was tested at NPL,
Teddington, UK, in the 1970s, Bailey. An example of the body plan for the series is
shown in figure 10 and the series covered the following range of speeds and hull
parameters.
Figure 10 - NPL series body plan
Speed. )2.36.0:,1.130.0:(,1.48.0: --- FrFrL
VR
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
931
1/3:1.7 6.7; 0.4( ); : 4.5 8.3b
B LC fixed
T- = -
LCB was fixed at 6.4% aft of amidship. Model length Lwl = 2.54m
Data for RR/ and Cr for a 30.5 m ship are presented in graphical form for a range of
L/B, L/1/3 and Fr . RR was derived by subtracting RF, using the ITTC line, from the total
resistance RT
In order to provide a more compatible presentation of the NPL data, CR values have
been calculated for the data where,
2...5.0 VS
RC RR
l= (13)
Table 8 Coefficients in the equation nR
LaC )(
3/1D
= for series 64 monohulls, Cb =0.45
Fn a n R2
0.4 36,726 -4,41 0.979
0.5 55,159 -4,61 0.989
0.6 42,184 -4,56 0.991
0.7 29,257 -4,47 0.995
0.8 27,130 -4,51 0.997
0.9 20,657 -4,46 0.996
1.0 11,644 -4,24 0.995
Table 9 Coefficients in the equation A value for nR
LaC )(
3/1D
= for series 64,
monohulls, CB = 0.55
Fn a n R2
0.4 926 -2.74 0.930
0.5 1775 -3.05 0.971
0.6 1642 -3.08 0.983
0.7 1106 -2.98 0.972
0.8 783 -2.90 0.956
0.9 458 -2.73 0.941
1.0 199 -2.38 0.922
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
932
The resulting values for CR are given in annex 1. Wetted surface area can be
estimated using an appropriate formula, as the following equations.
LCsS .. D= (14)
2)/.(01307.0)/.(0494.0538.2 TBTBCs ++= (15)
4 RESULTS
To verify the results of the programs that estimate effective horse power (EHP),
vessels with hull shapes of the type round-rilge, which is the most common among
the hull shapes of vessels carrying passengers on Amazon. A comparison of the
results of four different methods to estimate the EHP vessels aiming to identify which
method they best approximates the EHP regional vessels when compared to the
results found in the towing tank. The results obtained in the models were compared
with the results obtained in towing tank for three different hull shapes, which are the
most usual in the Amazon region, as the range of size and capacity.
For the most usual type of hull for small vessels, there was obtained the results
shown in graph where one can observe that the Shipflow [11] program, which uses
the finite element method, showed very good results at speeds between 5 and 9
knots, with small differences for speeds above 10 knots. The model NPL showed the
best results from among the proposed EHP estimated by regression and statistical
analyzes with very small errors when compared with the results of towing tank for the
range of 5 to 9 knots. The methods of Oortmerssen showed good applicability to the
speed of 8 knots. The Wolfson Unit method already presented satisfactory results at
speeds up to 6 knots.
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
933
Small Vessel (length up to 11m)
For the hull vessels of medium size, all models showed very good results at speeds up
to 10 knots. From 10 knots, only the model proposed by Oortmerssen stayed with
results with a significant difference in the results presented by the towing tank, the
other models showed very good results compared to the results obtained in the towing
tank. From 11 knots, the methods Wolfson Unit began to show higher values than
those obtained in the Towing Tank, around 20%. Since the NPL method only begins to
exhibit higher values for speeds above 12 knots the NPL method that provides the best
result among the methods using regression analysed for speeds up to 12 knots.
Medium Vessel (length between 12 and 25m)
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
934
For the results to the hull of a large vessel typical of the Amazon, it is found that the
finite element method of Shipflow is the closest to the results of the towing tank at all
speeds. All methods show good accuracy up to speed of 11 knots, and, among the
estimation methods using regression, the NPL method also gives good results
throughout the speed range studied.
Large Vessel (length between 26m up to 36m)
5 FINAL CONCLUSIONS
All estimation methods of EHP showed good results for speeds below 11 knots.
However for speeds between 11 to 15 knots, only the results of Shipflow, and NPL
present results close to those obtained from towing tank. The other prediction
methods EHP results show significant differences with those found in the towing
tank.
A more comprehensive investigation and greater universe of hull shapes must be
done to confirm the findings obtained in this work. It should also be emphasized that
the research was limited in the speed range of 5 to 15 knots, which is the speed
range higher incidence of regional vessels that operate in the Amazon.
Among the statistical methods have the following conclusions:
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
935
The method of Van Oortmerssen [10]is very good for EHP estimates of typical craft
of the Amazon to the speed range up to 10 knots and lengths up to 25m.
The WUMTIA (WOLFSON) method is more suitable for the range between 12m and
36m, but with always higher than estimates found in the towing tank.
The NPL method showed good accuracy for all speed ranges studied, which qualifies
it for use in predictive power (EHP) of vessels that are the carriage of passengers
and cargo in the Amazon region. However its accuracy is better for vessels greater
than 11m in length.
The Shipflow program that uses the finite element method gives good results also for
all speed ranges studied, and this program great applicability to estimate power
(EHP) of vessels typical of the Amazon.
There is also that the systematic series of NPL presents results very close to those
found by Shipflow for the length range between 12 and 36 m to all speeds, with the
advantage of much less computational effort and more practical method.
6 References
[1] Molland, A.F., Turnock, S.R. and Hudson, D.A. Ship Resistance and Propulsion
Practical Estimation of Ship Propulsive Power, Cambridge, 2011.
[2] Zhang Z, Liu H, Zhu S, Zhao F. Application of CFD in ship engineering design
practice and ship hydrodynamics. Conference of Global Chinese Scholars on
Hydrodynamics. 2006
[3] Gotman, A. Navigating the wake of past efforts. The Journal of Ocean
Technology.
Volume 2. Number 1. pp 74-96. 2007
[4] The Resistance Committee. Proceedings of the 24th IIT. Volume I. ITTC, 2005
U.K.
[5] Versteeg H.K, Malalasekera W. . An introduction to Computational Fluid
Dynamics. The finite Volume Method. Essex: Longman Scientific & Technical. 1995.
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
936
[6] Thompson J.F., Soni B.K., Weatherill N.P. . Handbook of Grid Generation. CRC
Press. 1999.
[7] Montgomery, D. Design and Analysis of Experiments. John Wiley & Sons, Inc.
2005.
[8] Molland, A.F., Wilson, P. A., Taunton, D.J., Chandraprabha, S. and Ghani, P.A.,
Resistance and wash measurements on a series of high speed displacement
monohull and catamaran forms in shallow water. International Journal of Maritime
Engineering, Transactions of RINA, 146(A2), 2004
[9] Tran, T., Harris, C. J., and Wilson, P. A., A vessel management expert system.
Journal of Engineering for the Maritime Environment, Proceedings of I. Mech. E,
216(M), , 161-177. 2002.
[10] Van Oortmerssem, G., A power prediction method and its application to small
ships, publication no 391 of NSMB, 1971.
[11] Shipflow, users manual, FLOWTECH, Gothenburg Sweden,2001.
Annex 1
-
Libro de Ponencias y Conferencias del XXIII Congreso Panamericano de Ingeniera Naval, Costa Afuera e Ingeniera Portuaria COPINAVAL 2013
937