Trans RINA, Vol 157, Part A3, Intl J Maritime Eng, Jul-Sep 2015 HYDRODYNAMIC HULL FORM DESIGN SPACE EXPLORATION OF LARGE
MEDIUM-SPEED CATAMARANS USING FULL-SCALE CFD (DOI No: 10.3940/rina.ijme.2015.a3.331)
M Haase, J R Binns, N Bose, Australian Maritime College, University of Tasmania, Australia, G Davidson, Revolution Design Pty Ltd, Australia, G Thomas, University College London, UK, and S Friezer, Stuart Friezer Marine, Denmark
SUMMARY
Large medium-speed catamarans are a new class of vessel currently under development as fuel-efficient ferries for sustainable fast sea transportation. Appropriate data to derive design guidelines for such vessels are not available and therefore a wide range of demihull slenderness ratios were studied to investigate the design space for fuel-efficient operation. Computational fluid dynamics for viscous free-surface flow simulations were utilised to investigate resistance properties of different catamaran configurations having a similar deadweight at light displacement, but with lengths ranging from 110 m to 190 m. The simulations were conducted at full-scale Reynolds numbers (log(Re) = 8.9 – 9.6) and Froude numbers ranged from Fr = 0.25 to 0.49. Hulls of 130 m and below had high transport efficiency below 26 knots and in light loading conditions while hulls of 150 m and 170 m showed benefits for heavier displacement cases and speeds up to 35 knots. Furthermore, the study concluded that the lowest drag was achieved with demihull slenderness ratios between 11 and 13.
NOMENCLATURE CFD
ITTC
HEAVY LIGHT
1. computational fluid dynamics
DTMB 5415 David Taylor Model Test Basin combatant model
International Towing Tank Conference indicates heavy displacement case indicates light displacement case
MEDIUM indicates medium displacement case RANSE SST dh
exp oa
AT/AX B
CB CP CT
dwt Fr g L
RT s
s/L SW
T
TE V
y+ ε
ηpropulsion
indicates values for single demihull indicates value from model test indicates values for entire vessel transom immersion ratio (-) beam (m)
block coefficient ( - ) prismatic coefficient ( - )
Pinstalled Re
L/1/3
total resistance coefficient ( - ) deadweight tonnes ( t ) length Froude number( - ) gravitational constant (m s-2) length of vessel (m) slenderness ratio ( - )
installed engine power (MW) Reynolds number ( -) total resistance (N)
transport efficiency (dwtgU)/Pinstalled velocity ( m s-1 )
separation of demihull centrelines (m) demihull separation ratio ( - ) wetted surface area (m2) draft (m)
dimensionless first cell height ( - ) relative deviation ( - )
overall propulsive efficiency ( - ) density of water (kg m-3)
volumetric displacement (m3)
Reynolds-Averaged Navier-Stokes Eqn shear stress transport
INTRODUCTION
Large medium-speed catamarans are a new class of ships for sustainable RoPax transportation development
which are a of current high-speed catamarans.
Contemporary high-speed catamarans are characterised by two demihulls with a large superstructure to accommodate the payload. They are propelled by waterjets, have a length of up to 125 m and operate at speeds of 40 knots and above, usually at Froude numbers of Fr = 0.6 – 1.0. Compared to monohulls the main advantages comprise high transverse stability and large deck areas in conjunction with slender demihulls that enable low wave-making resistance and low added resistance in waves, so that combined with good manoeuvrability [1] they
provide effective fast sea
transportation. However, the high speeds of these craft are not desirable from an environmental point of view [2].
The continual increase in fuel costs, society’s increasing awareness of environmental sustainability, and official regulations to limit emissions, such as MARPOL 73/78 Annex VI [3], have raised the demand for highly fuel- efficient vessels. It is proposed that using the specific low-drag advantages of high-speed catamarans at lower operating speeds would provide more efficient vessels with low fuel usage. Nevertheless, little is known about most appropriate hull form in this lower speed regime for vessels
that have traditionally operated at high Froude been number. So this
designed and study
investigated appropriate macro design parameters for medium-speed catamarans to provide maximum fuel- efficiency through minimising resistance.
separation (s/L) have been found to be two of the most important design parameters influencing the resistance of fast displacement catamarans demihulls
Demihull slenderness ratio (L/dh [4],[5] with slender being the key to minimise environmental impact of catamarans [6]. These two parameters have ©2015: The Royal Institution of Naval Architects A-161 1/3) and demihull
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