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Procedia Engineering 00 (2017) 000±000
www.elsevier.com/locate/procedia
1877-7058 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of the 10th International Conference on Marine Technology.
10th International Conference on Marine Technology, MARTEC 2016
Optimizing Trimaran Yacht Hull Configuration Based on Resistance and Seakeeping Criteria
G.A.P. Poundra
a*, I.K.A.P Utama
b, D. Hardianto
a, B. Suwasono
aaHang Tuah University, Jl. Arief Rahman Hakim No.150, Surabaya, Indonesia
bSepuluh Nopember Institute of Technology, Jl. Raya ITS, Surabaya, Indonesia
Abstract
An investigation into the optimization of a trimaran yacht, which is equipped with axebow, was carried out numerically. The study was focused on the analysis of resistance and seakeeping which can provide the best performance to the yacht, based on those two criteria. The numerical study used Ansys Fluent code for resistance analysis and seakeeper from Maxsurf for seakeeping analysis. The overall results were compared with published data for validation purposes. The results are believed to be useful for the development of the marine-tourism, which is now growing quite rapidly in Indonesia.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of the 10th International Conference on Marine Technology.
Keywords:Trimaran, Axebow, Resistance, Seakeeping
Introduction
The use of multihull vessels, including catamaran and trimaran, has received considerable attention in the last 40 years due to its better transverse stability and providing wider deck area compared to monohull vessels [1]. One of the multihull vessels is called trimaran, which is a multihull boat that comprises a main hull and two small outrigger hulls attached to the main hulls are determined into two kinds [2], namely symmetric and asymmetric hull. One of the most trimaran application is called yacht, which is a recreational boat or ship. The term originates from Dutch word jacht ³KXQW´ DQG ZDV RULJLQDOO\ GHILQHG DV OLJKW DQG IDVW VDLOLQJ YHVVHO XVHG E\ WKH 'XWFK QDY\ WR SXUVXH pirates and other transgressors [3]. In modern use, yacht designates into two different classes of watercraft: sailing and power boats. In order to reduce drag and improve seakeeping quality on trimaran, some work showed the effective use of axe-bow [4]. By definition, axe-bow is the wave-SLHUFLQJW\SHRIDVKLS¶VERZFKDUDFWHUL]Hd by a vertical stem and relatively long and narrow entry (front hull).
*Corresponding author, Tel. +6287853637298 Email Address: [email protected]
2 G.A.P. Poundra, I.K.A.P. Utama, D.Hardianto, B.Suwasono / Procedia Engineering 00 (2017) 000±000 The Design
In order to satisfy the needs of a comfortable vessel and help tourist in marine-tourism transportation sector, a design model of trimaran based on resistance and seakeeping criteria is developed. The principal particulars and body plan of model are shown in Figs.1 and 2 and Tables 1 and 2. Separation between hull is made fixed on the length of main-hull and the S/L is 0.078.
.
Fig. 1 Trimaran Body Plan
Fig.2 Trimaran A,B and C Breadth Plan
For the first and the second models are technically the same models. The difference only lies on the position of outrigger hulls. Meanwhile, the third model uses asymmetrical (flat-side outside) outriggers.
Table 1. Trimaran Vessel A,B and C Principle Particulars
Designation Vessel A Vessel B Vessel C Units
Length Over All 54.5 54.5 54.5 meters
Breadth Moulded 15 15 m 13.59 meters
Draught
Displacement vessel Cruising Speed
1.6 100.6 17.5
1.6 m 101.2 17.5
1.6 83.91 17.5
meters tones knots Resistance Analysis
The resistance analysis was carried out by using Computational Fluids Dynamics (CFD) software. CFD is a branch of fluids mechanics that uses numerical analysis and algorithms to solve and analyze problems that involve fluids flow, and computers are used to perform the calculations which were required to simulate the interaction of liquids and gases with surfaces defined boundary conditions [5]. In all of these approaches, the same basic procedure is followed.
1. During pre-processing [6]:
a) The geometry of the problem is defined.
b) The volume occupied by the fluid is divided into discrete cells (mesh).
c) The physical model is defined. Boundary condition is defined.
2. The simulation is started and the equations are solved iteratively as a steady-state or transient.
3. Post-processor is used for analysis and visualization of the resulting solution.
CFD analysis was carried out in order to figure out the flow movement phenomenon thus contributes to the total resistance measurements. Several works on the resistance investigation have been done such as reported by Utama in 1999 [7]. The equation that being used to express the flow movement phenomenon is the Navier-Stokes equation.
In the term of mass conservation and the fluids flow continuity which state [8]:
(2)
Since the integral is valuated at a fix instant of time, the distinction that V is a material volume is unnecessary at this stage. Moreover, this volume can be composed of an arbitrary group of fluids particles; hence, the integrand itself is equal to zero throughout the fluid. Thus the volume integration can be replaced by a partial differential equation expressing conservation of mass in the form.
(3)
The approximation based on knowledge of the properties of turbulence flow to give approximate time-averaged solutions to the Navier-Stokes equations, which explained in the Reynolds Average Navier-Stokes (RANS). This equation can be written in the following notation [9]:
(6)
In the process of turbulence model analysis, the K-epsilon model was used. The K-epsilon (k-İ is the most common model used in Computational Fluids Dynamics (CFD) to simulate mean flow characteristics for turbulent flow conditions. It is a two equation model which gives a general description of turbulence by means of two transport equations (PDEs). The original impetus for the K-epsilon model was to improve the mixing-length model, as well as to find an alternative to algebraically prescribing turbulent length scales in moderate to high complexity flows.
The transport equation for standard K-epsilon (k-İ can be express as follows:
For turbulence kinetic energy k (TKE)
(7)
The simulations of the CFD were running quite successfully, and the results of each models comes with different characteristics that can be shown in the tables and figures below:
( i) 0
V V i
d dV dV
dt t x
U ª«¬wwUww UP º»¼
³³³ ³³³
( i) 0
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i i i
j i j
j i j j j
U U p U
U u u
t x x x x x
w w w w w
w w w w w w
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1 3 2
( i) t ( k b)
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t x x H x Hk H HU k H
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w w w w
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¬ ¼
4 G.A.P. Poundra, I.K.A.P. Utama, D.Hardianto, B.Suwasono / Procedia Engineering 00 (2017) 000±000
Fig.3 Trimaran A,B and C CFD Results
From the results of the simulation A, we know that the model is having quite low resistance due to the shape of the KXOOZKLFKLVTXLWHVWUHDPOLQHVRWKDWYHVVHO¶VPRYHPHQWLVQ¶WGLVWXUELQJWKHIOXLGVIORZDORQJWKHYHVVHO¶VERG\
Compared to vessel A, vessel B is having a lower pressure because of the outrigger hulls position which are located in the nearest point of the midship. This position leads to a lower pressure and a higher turbulence kinetic energy (TKE) due to the fluids flow form of the ship. The simulation also shows that the vessel C is having the lowest pressure among the other vessels due to the shape of the outrigger hulls which make this model having the lowest displacement. Based on the CFD simulations for resistance analysis, the value of the total resistance in various froud numbers for each vessel can be shown as follows.
Table.3 Trimaran A,B and C Total Resistance
Fig.4 Trimaran A,B and C Total Resistance Seakeeping Analysis
The seakeeping analysis came up with several results for vessel A, B and C which will be explained in the tables based on the data from maxsurf motion (seakeeper). This research focused on three aspects of seakeeping i.e.
heaving, pitching and rolling in general and the waves are assumed came from three different directions, those are
Item Vessel A Vessel B Vessel C Units
Pressure 9.48803e+08 3.58888e+08 -210694 Pa
Density
Turbulence Eddy Diss.
Turbulence Kinetic Energy Air Volume Fraction
1025 18.4742 83.1993 0.528714
1025 22095.8 68775.4 1
1025 159201 6.72665e+06 1
kg m-3 m2 s3 J kg-1
Velocity 3318.68 3318.68 3318.68 m s-1
Speed (Knots)
Fr VesselA Vessel B Vessel C 0
0.438
0 0.010
0 42.86
0 40.38
0 38.72 2.188
4.375 6.563 8.750
0.049 0.097 0.146 0. 195
862.34 3163.91 6759.77 11634.13
815.71 2996. 18 6404.81 11037.19
783.55 2878.98 6759.77 10615.00 11.375
13.563 15.750 17.500
0.253 0.302 0.350 0.389
19473.38 28225.64 39670.10 51197.06
18557.19 27092.22 38415.10 49826.66
17845.23 25933.61 36374.19 46643.02
0 10 20 30 40 50 60
Fr (x0.001) 0 10 49 97 146 195 253 302 350
RT (kN) VesselA
Vessel B Vessel C Table.2 Trimaran A,B, and C CFD Results
Û Û DQG Û in regular waves. The spectrum of the wave analysis was using the Pierson-Moskowitz wave spectrum. Mathematically those three aspects can be expressed as follows:
Heaving general equation [10]:
The components of the equation above can be described, as follows:
Pitch general equation [10]:
Rolling general equation [10]:
Beside WKRVHHTXDWLRQVDERYHLQVHDNHHSLQJDQDO\VLVWKHUH¶VDUDWLRNQRZQDV5HVSRQVH$PSOLWXGH2SHUDWRU5AO).
RAO is the ratio between amplitude and the ship motions (either translation or rotation) to the wave amplitude to a certain wave frequency. Mathematically RAO can be expressed as [10]:
(16)
For the added resistance calculation, in this research the salvesen method was used. The salvesen added resistance method can be expressed as:
(17)
)URPWKHVLPXODWLRQWKDWKDGEHHQGRQHWKHUHVXOWVIURPHDFKZDYH¶VGLUHFWions can be shown in the table.5, 6 and 7.
For the Added resistance from each models, will be attached as additional data. tables for each wave coming directions to the ships.
7DEOH7ULPDUDQ9HVVHOV506Û 7DEOH7ULPDUDQ9HVVHOV506Û
Table.7. Trimaran Vessel RMS Û
The Correlation between Seakeeping Criteria and Resistance
The results of each simulation finally lead us to some correlations between them, which can be shown as follows.
Motion Vessel A Vessel B Vessel C Heave [m]
Pitch [rad]
0.276 0.022
0.235 0.021
0.229 0.024
Roll [rad] 0.225 0. 225 0.241
Motion Vessel A Vessel B Vessel C Heave [m]
Pitch [rad]
0.208 0.014
0.411 0.042
1.13 0.024
Roll [rad] 0 0 0
Motion Vessel A Vessel B Vessel C
Heave [m]
Pitch [rad]
1.057 0.186
0.673 0.099
0.299 0.174
Roll [rad] 0 0 0
0
cos
eaz bz cz F Z t
(14)
0
cos
ed T e T h T M Z t
(15)
2
2 0cos e
d d
c M t
dt dt
I I
D D I Z
0 0
2
0
/
0w
RAO k g
T T
[ Z [
2 1 1
1 2
1 sin
2
LR g U n dl
g
U § ¨ Z · ¸ -
© ¹ ³
6 G.A.P. Poundra, I.K.A.P. Utama, D.Hardianto, B.Suwasono / Procedia Engineering 00 (2017) 000±000 Table.7 Vessel A RMS and Resistance Table.8 Vessel B RMS and Resistance
Items Û Û Û
Heave [m]
Pitch [rad]
0.208 0.014
0.276 0.022
1.057 0.186
Roll [rad] 0 0.225 0
Added Resistance 129.237 193.877 231.066
Table.9 Vessel C RMS and Resistance
Items Û Û Û
Heave [m]
Pitch [rad]
0.411 0.042
0.235 0.021
0.299 0.174
Roll [rad] 0 0. 225 0
Added Resistance 130.881 201.854 203.181
Tables 7, 8 and 9 showed WKDWWKHÛZDYHKHDGLQJVJDYHPRUHEDGLPSDFWERWKLQWKHDGGHGUHVLVWDQFHWR the ship due to the hull form in the ship stern is bigger than the form of the bow. Tables 13,14 and 15 also showed WKDWWKHÛJDYHWKHZRUVWLPSDFWGXHWRWKHH[LVWHQFHRIWKHKHDYHSLWFKDQGUROOPRWLRQVZKLFKWKHÛDQGÛ only having heave and pitch motion only.
Conclusion
The study of the trimaran hull configuration effects to her resistance and seakeeping criteria has been demonstrated by using Ansys Fluent and Maxsurf Motion (Seakeeper) quite successfully. From results of the simulations led us to some conclusions as follows:
1. The lighter the ship, the worse the seakeeping performance.
2. The position of the outrigger hulls will cause some differences in the resistance values of each models, although each models having the same main hull geometry and a constant separation ratio.
3. The fluids flow form that flows along the ship body shall affecting the resistance values.
4. The correlation between seakeeping and resistance of the ship in the constant S/L ratio lies on the fluctuation of the WSA as well as the ship acceleration.
Acknowledgement
Acknowledgements Aimed shown to Rector of Hang Tuah University and Hang Tuah Model Boat (HTMB) Community.
References
[1] Murdijanto, Utama, I K A P and Jamaluddin, A. An investigation into the resistance / powering and seakeeping characteristics of river catamaran and trimaran, Makara Seri Teknologi, Vol 15, No.1, 2011.
[2] Natanael Martian DwiSunarto, UntungBudiarto, EkoSasmitoHadi, Hybrid Trimaran Tourist Boat Design for Karimunjawa Sea, Indonesia, 2014.
[3]Antonia Fracer, Royal Charlest, Alfred a Knopf, Greener Books, London, United Kingdom, 1979.
[4] J.A. Keuning, J.Pinkster and F. Van Walree, Further Investigation into the Hydrodynamic Performance of the AXE Bow Concept, Maritime Research Institute Netherlands, HSMV, 2002.
[5] Jameson A. and Caughey D., "A Finite Volume Method for Transonic Potential Flow Calculations," AIAA paper 77-635, presented at the Third AIAA Computational Fluid Dynamics Conference, Alburquerque New Mexico, June 1977.
[6] Richard Benny Luhulima, I Ketut Aria PriaUtama, Aries Sulisetyono, Experimental Investigation into the Resistance Components of Displacement Trimaran at Various Lateral Spacings, International Journal of Engineering Research & Science (IJOER), 2016
[7] Utama, I K A P, (1999), An Investigation into the Viscous Resistance Components of Catamarans, PhD Thesis, University of Southampton, UK.
[8] J.N. Newman, Marine Hydrodynamics, The MIT Press, London, England, 1977.
[9] Gabriel David Weymouth, Robert Vance Wilson, and Frederick Stern, RANS Computational Fluids Dynamics of Pitch and Heave Ship Motions in Head Seas, Iowa, Journal Of Ship Research, Vol.49, No.2 USA, June 2005.
[10] Rameswar Bhattacharya, Dynamics Of Marine Vehicles Vol. II A, A. Wiley-Interscience Publication, Canada, 1978.
Items Û Û Û
Heave [m]
Pitch [rad]
1.13 0.024
0.229 0.024
0.673 0.099
Roll [rad] 0 0.241 0
Added Resistance 130.881 153.576 203.181