Experimental and Numerical Study of Effects of the Application of

Hydrofoil on Catamaran Ship Resistance

Ahmad Firdhaus

1,a

, I. Ketut Suastika

Department of Naval Architecture, Institut Teknologi Sepuluh Nopember, Indonesia

Keywords: Catamaran, CFD, Hydrofoil, Resistance, Towing-tank Test.

Abstract: The use of hydrofoil on a catamaran can reduce the ship's resistance at a certain speed. The reduction of ship

resistance occurs because of the lifting force that lifts the ship's hull above the waterline to reduce the wet

surface area. This research aims to study the effect of adding hydrofoil in the hull of a catamaran on the ship's

total resistance using experimental and numerical CFD methods. A 44m passenger catamaran was considered

with two variations of hydrofoil: one hydrofoil on the bow section and two hydrofoils (one on the bow section

and one on the stern section). The hydrofoil is rectangular NACA 641-212 section and aspect ratio of 16,34.

The results indicate increasing ship resistance instead of decreasing on the catamaran with the hydrofoil. At

service speed (Fr=0,7), the Total resistance value occurs in case 1 (catamaran without hydrofoil) is 114.59

kN, case 2 (catamaran with added one foil on the bow section), and case 3 (catamaran with added foil on both

bow and stern section) are respectively 31% and 59% higher than the catamaran without hydrofoil. These data

show that not all existing catamaran vessels can be added hydrofoil between the demihulls.

1 INTRODUCTION

Abbreviation Hysucat stands for Hydrofoil Supported

Catamaran and describes a new High-Speed Small

Craft, a seagoing catamaran with a hydrofoil

arrangement the two demi-hulls which carries a part of

the craft's weight at speed. Vessels of this type have

greater efficiency than fast boats or varieties of a

catamaran with a gastric form V. "Hysucat" shows a

reduction in propulsion power and has good seakeeping

characteristics in rough water (Hoppe, 1995).

Based on research on variations in the type of

hydrofoil on catamaran vessels, catamaran vessels'

performance, especially on ship resistance, has

increased efficiency, as evidenced by resistance

improvement of up to 40% based on the output from

several research projects (Hoppe, 2001).

Research and development related to Hysucat

ships (hydrofoil supported catamaran) and Hysuwac

(hydrofoil supported watercraft) began in the late

1970s or early 1980s at Stellenbosch University,

South Africa, led by Prof. Karl Gunter Hoppe

(Hoppe, 1987). Aside from Hoppe, the research

results related to the use of foil on catamarans were

also reported in (Calkins, 1984) and (Suastika et al.,

2018) conduct numerical simulations of hysucat

mono foil vessels using CFD. The simulation results

show that the position of hydrofoil placement in the

longitudinal direction dramatically affects the size of

the ship's resistance. The most optimum position is

the position just below the Center of Gravity (CoG)

of the ship.

The latest technology in ships has been developed

in a variety of conventional forms, including one with

Hydrofoils, Surface Effect Ships (SES), Air Cushion

Vehicles (ACV), and Smal Waterplane Area Twin

Hulls (SWATH). The difference between various

concepts is the method to help the weight of the ship.

Three basic methods, namely, (1) static lift

(Buoyancy), (2) supported static lift (lift fans), and (3)

dynamic lift force (hydrofoils planing hull). The

results of ship technology development with this

method. 95-100% of the ship's weight is assisted by

one of the three methods above (Hoppe, 1989).

NACA (National Advisory Committee for

Aeronautics) Aerofoil is an aerodynamic body shape

that functions to give a certain lift force to a body. An

aerofoil is an aerodynamic form that aims to produce

a large lift force with the smallest drag force possible.

When an aerofoil is passed by fluid flow, because of

the influence of the interaction between fluid flow

and the surface, variations in velocity and pressure

will occur along the top and bottom surfaces as well

104

Firdhaus, A. and Suastika, I.

Experimental and Numerical Study of Effects of the Application of Hydrofoil on Catamaran Ship Resistance.

DOI: 10.5220/0010854400003261

In Proceedings of the 4th International Conference on Marine Technology (senta 2019) - Transforming Maritime Technology for Fair and Sustainable Development in the Era of Industrial

Revolution 4.0, pages 104-110

ISBN: 978-989-758-557-9; ISSN: 2795-4579

as the front and rear. The pressure difference between

the upper and lower surfaces gives rise to a resultant

force whose direction is perpendicular to the direction

of the flow of fluid, and this force is called lift force.

The difference in pressure between the front and back

will result in a resultant force in the direction that is

in line with the direction of the flow of fluid, and this

force is called a drag force (Hoppe, 1991).

Catamarans tend to have low water draught so that

the ship can be operated in shallow water. Slender hull

shape can reduce the occurrence of wave wash

compared to monohull vessels. The components of the

catamaran ship resistance have a more complex

phenomenon than a monohull because there is an

interaction effect between the two hulls of the ship,

which causes ship resistance interference. The

empirical formula used is based on the equation from

the study in (Jamaluddin et al., 2013), which is a

modification of the method (Molland et al., 1996).

The purpose of this study is to investigate the effects

on the ship resistance of the positioning of the

hydrofoil arrangement between the two demi-hulls.

Studies on the hydrofoil positioning in the longitudinal

directions were reported in (Suastika et al., 2018). This

study pursues that reported in (Suastika et al., 2018) but

utilizing different arrangement as case 1 (catamaran

without hydrofoil), case 2 (catamaran with added one

foil on the bow section), and case 3 (catamaran with

added foil on both bow and stern section). The results

can enrich the literature on the applications of

hydrofoil catamaran.

2 METHOD

The ship particulars are summarised in Table 1. The

study utilizes CFD simulations and towing test

experiments.

Table 1: Ship Particular.

Princi

al Dimension Catamaran Demihull

LWL 44.00 m 44.00 m

B 20.6 m 3.00 m

T 1.40 m 1.40 m

3.80 m 3.80 m

28 knot 28 knot

Cb 0.491 0.491

Displacement 185.50 ton 92.75 ton

Furthermore, the ship's resistance analyses with the

variation of the number of foil placed on between the

catamaran demi-hull

2.1 Modeling with CAD Software

From the main dimension data of the ship model, the

ship body modeling was made with the help of a CAD

modeler, as shown in figure 1 below. Figure 1 shown

the 3D geometry of the ferry catamaran with one foil

on the bow section of the ship as a wireframe view.

3D geometry should be similar to a real ferry

catamaran so it can be used for numerical simulation

and represents the real condition. In this research,

there are three variations from the original condition

is catamaran without foil. Variation 1 is a catamaran

with one foil on the bow section of the ship, and

variation 2 is a catamaran with two foils (1 on the bow

section and one on the stern section). NACA 641-212

is used for added foil. Places 1m below draught

(1.4m) with 1m cord and 17.3m span.

Figure 1: Front view (upper) and diagonal view (below) of

Geometry of catamaran vessel model (Case 1 - 1 foil at bow

section) using CAD modeler.

2.2 CFD Simulation of the Foil NACA

-212

Simulations of the foil alone were undertaken to

measure lift force produced by foil NACA 641-212

with 1m cord and 17.6m span on different speed

based on catamaran service speed for preliminary

measurement to get information about how much lift

force from foil before it is assembled on between

demihull catamaran, from this, we can estimate WSA

reduction because of the lifted hull, trim that will

happen to the ship, and total ship resistance.

Experimental and Numerical Study of Effects of the Application of Hydrofoil on Catamaran Ship Resistance

105

Figure 2: Preview Mesh of the NACA 641-212 foil on

boundary domain from pre-processing of CFD simulation

with hybrid mesh consists of the unstructured element on the

domain and structured element on boundary layer and foil.

The boundary conditions of the computational

domain are as follows (Versteeg & Malalasekera,

2007). The inlet boundary, located at 1-c upstream

from the leading edge (where c is the chord length),

is defined as a uniform flow with velocity equaling

the ship/foil’s velocity. (In the simulations, the foil is

at rest, but the water flows.) In the outlet boundary, at

a location 4-c downstream from the trailing edge, the

pressure equals the undisturbed (hydrostatic)

pressure, ensuring no upstream propagation of

disturbances (Mitchel et al., 2008). The boundary

condition on the foil’s surface is defined as a no-slip

condition. The boundary conditions on the top and

bottom walls (at a distance of 2-c above and below

the foil, respectively) and on the side walls

(approximately 7-c away from the side of the model)

are defined as free-slip condition. Furthermore,

because the foil is fully submerged at a relatively deep

submergence elevation (the foil’s thickness is much

smaller than the submerged depth), and in order to

reduce the time of convergence, free surface effects

(generation of waves) were not modeled in this case.

2.3 CFD Simulation of the Catamaran

with and without Foil

The process of numerical simulation on

Computational Fluid Dynamic starts from making a

hull model. Modeling using the CAD software, then

the file is exported in the form of a file .igs. The model

used must be solid. After the model is finished, the

work continues using numerical simulations. The

numerical simulation software used is software based

on Computational Fluid Dynamic. These simulation

steps are divided into several stages, including

Geometry, Mesh, Setup, Solution, and Result.

Figure 3: Imported Geometry solid modeling of catamaran

without foil on CFD pre-processor phase from CAD

modeler.

Figure 4: Imported Geometry solid modeling of a

catamaran with one foil on CFD pre-processor phase from

CAD modeler.

Figure 5: Imported Geometry solid modeling of a

catamaran with one foil on CFD pre-processor phase from

CAD modeler.

Figures 3 to 5 show the geometry model after

imported to CFD software from CAD software. It

must be solid so CFD software can read the geometry

fully correct and ready to simulate. After the running

or simulation process is complete, the results can be

seen in the result stage. The results obtained are the

resistance value of the ship, the model, and

visualization of the flow on the free surface and

station behind the hull.

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106

2.4 Towing-tank Experiments

Towing tank experiments were held in the

Hydrodynamic Laboratory of the Faculty of Marine

Technology, ITS Surabaya, Indonesia, to verify the

results from CFD simulations. The dimensions of the

towing tank are 50m in length, 3m in width, and 2m

in depth.

1:40 geometrical scaled Ship Model were

designed and manufactured for the ship hull and the

foil. Fiberglass-reinforced plastic was used to make

the ship model, and the foil was made from copper.

The model’s resistance was measured by using a load

cell. The load cell was connected to a voltage

amplifier, which was in turn connected to a computer

network in the control room. Before carrying out a

measurement, the load cell was calibrated by using a

mass of 0.5kg. Five ship speeds were tested: 0.87,

1.16, 1.46, 1.74, and 2.037 m/s (full-scale speeds: 12,

16, 20, 24, 28 knots). Figure 7 shows a photograph of

the model being towed at a speed of 1.16 m/s (full-

scale speed: 16 knots; Fr = 0.4).

Figure 6: Model 2 of a catamaran with one foil on the bow

section of the demihull catamaran before tested on towing

tank on 16-knot speed (1.16m/s).

3 RESULTS AND DISCUSSION

3.1 Foil Characteristic

Table 2 summarizes the effect of different foil angels

of attack on the lift-to-drag ratio as obtained from

simulations of the foil alone with an angle of attack

from -8⁰ to 24. The results show that, for the same foil

size (aspect ratio), the lift-to-drag ratio of NACA 641-

212 is increasing along with the rise of the angle of

attack until 4⁰ and then decreasing. Furthermore, the

vane characteristics were obtained from CFD

simulations of foil alone. To verify the CFD results,

these are compared with the theoretical results.

The shifts in lift and drag coefficients due to finite

span are given as follows (White, 2011). For a given

, the horizontal shift in α due to the finite span as

compared with the infinite span case is given as:

∆𝑎 

𝐶



𝜋𝐴

(1)

Furthermore, for a given 𝛼, the increase in C

due

to the finite span as compared with the infinite span

case is given as:

∆𝐶





𝐶





𝜋𝐴

(2)

In Equations (1) and (2), the C

is the drag

coefficient, C

is the lift coefficient, α is the angle of

attack and A is the aspect ratio. Then the results of C

from CFD are compared with C

from experimental

calculations that have been carried out by others to

ensure that calculations using CFD can be trusted by

plotting the graphic of C

from CFD and experiment

such in Figure 7.

Figure 7: Lift and drag coefficients for NACA 641-212

section (theoretical results with infinite aspect ratio A)

compared with NACA 641-212 vane with an aspect ratio of

17.3 obtained from CFD simulations (Re

= 5.0 x 106).

Table 2: Foil NACA 641-212 Characteristic.

αDra

(

)

Lift

(

)

Cl L/D

-8 32.35 -590.27 0.03 -0.62 -18.25

-4 16.79 -239.12 0.01 -0.25 -14.24

0 13.67 116.74 0.01 0.12 8.54

4 28.15 470.71 0.03 0.50 16.72

8 47.48 782.32 0.05 0.83 16.48

12 93.89 1028.04 0.10 1.09 10.95

16 148.51 1138.18 0.15 1.20 7.66

20 258.75 979.08 0.27 1.04 3.78

24 419.03 712.66 0.44 0.75 1.70

Experimental and Numerical Study of Effects of the Application of Hydrofoil on Catamaran Ship Resistance

107

Figure 7 shows the lift and drag coefficients for

NACA 641-212 section with infinite span compared

with NACA 641-212 section and aspect ratio A =

17.34. The lift curve slope for



between -8° and 12°

for the infinite span case is approximately 0.1 per

degree and stall takes place at



approximately 14°

according to the theoretical prediction (Abbot & Von

Doenhoff, 1959).

Table 3 summarizes the lift forces that occur on

the foil when it is simulated under several ship speed

conditions as obtained from foil simulations only

without catamaran, with the angle of attack α = 2⁰,

chord 1m length and span 17.3m. The results show

that, for the same foil size (aspect ratio), the higher

the speed of the ship, the higher the lift force

produced by the foil. NACA 641-212 foil has a

greater lift when it's simulated on service speed

(Fr=0.7).

Table 3: Lift force of foil NACA 64

-212.

V (Knots) V (m/s) L (kN) D (kN)

0.3 12 6.17 67.83 11.61

0.4 16 8.23 119.71 20.72

0.5 20 10.29 184.53 32.75

0.6 24 12.35 249.25 50.48

0.7 28 14.40 327.88 70.32

Table 4 summarizes the lift force that occurs on

the foil when it is simulated under some conditions of

ship speed obtained from the simulation when the foil

is on a catamaran, with the angle of attack α = 2⁰,

chord 1m length, and span 17.3m. The results show

that, for the same foil size (aspect ratio), the higher

the speed of the ship, the higher the lift force

produced by the foil. The value of this condition is

greater than the lift and drag on foil-only condition

because when the foil is attached to the catamaran

hull, the foil condition seems to have a wingtip

because both ends of the foil are covered by demihull.

Table 4: Lift force of foil NACA 641-212 on the catamaran.

Fr Vs. (knot) Vs (m/s)

Lif

(kN)

1 Foil 2 Foil

0.3 12 6.17 69.57 124.86

0.4 16 8.23 149.62 233.42

0.5 20 10.29 246.97 425.51

0.6 24 12.35 352.14 612.88

0.7 28 14.40 451.14 707.15

3.2 Ship Resistance with and without Foil

Results of resistance for the ship with vane are

presented in this section. A comparison between the

CFD and towing test results are shown in Figure 9.

Figure 8: Model 2 of a catamaran with one foil on the bow

section of the demihull catamaran being tested on towing

tank at 16-knot speed (1.16m/s).

It can be shown in Figure 9 below that trim

occurred on the model because of the effect of bow

foil. The result of the Ship resistance analysis using

CFD and Experiment was gathered and then process

to get the final data. In figure 8 above is Case 2 of a

catamaran with one foil on the bow section of the

demihull catamaran being tested on towing tank at a

16-knot speed (1.16m/s). It can be shown in Figure 9

below that trim occurred on the model because of the

effect of bow foil. The percent relative error between

Ship resistance value from each model with various

speeds from CFD calculation and towing tank

experiment can be seen on the table below.

Table 5: Percent relative error between the CFD results and

experiment.

Case 1 Case 2 Case 3

0.3 4.80 0.88 4.84

0.4 3.48 3.16 2.64

0.5 1.10 4.12 1.96

0.6 1.40 3.30 1.22

0.7 3.40 4.08 2.00

Table 6: Percent increase of total resistance compared

between case without foil (Case 1) and case with foil (Case

2) and (Case 3) based on CFD result.

Case 2 Case 3

0.3 41.11 98.94

0.4 39.27 87.49

0.5 36.05 82.21

0.6 34.09 77.42

0.7 31.04 59.32

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Figure 9: Total ship resistance from 3 various models

of a catamaran with and without foil with different

speeds (Fr=0.3-0.7).

Line with black dash is resistance for catamaran

without foil, dash dots line is Resistance for a

catamaran with one foil on bow section, the straight

line is a catamaran with two foil (1 on the bow and

quarter span on the stern section of each demihull),

and node without line results from the experiment.

The calculation results and the graph image above

show the difference in the resistance value of each

ship model according to the Froude number and the

speed of each ship model. As table 5 show that there

is no reduction in ship resistance because of added

foil, a catamaran with two foil is higher than a

catamaran without foil. Based on the literature

(Calkins, 1984; Hoppe, 1982, 1989, 1991, 2001), the

effect of added foil on the ship hull will reduce the

total resistance at a certain speed. In this study, the

effect of adding foil has not reached a state where the

addition of lift force is greater than the addition of

drag force due to the addition of foil, so a higher speed

is needed to achieve this condition. But as the speed

going higher, it will consume much power, so the

efficiency will not be optimum.

4 RESULTS AND DISCUSSION

Based on CFD Simulation and Towing tank

experiment that has been done on 3 different cases.

(K1) catamaran without foil, (K2), 1 catamaran with

1 foil on the bow section, (K3), a catamaran with 1 in

the bow section, and 1 in the stern section show that

the added foil significantly affect the catamaran’s

total resistance. Generally, hydrofoil on a ferry

catamaran increases the total resistance produced by

the ship at service speed. The highest resistance value

occurs in the case catamaran with foil on the ship's

bow and stern section (K3). Total resistance value

happens in case 1 as the existing catamaran without

foil is 114.59 kN at service speed, case 2 (1 foil)

design of catamaran with added 1 foil on the bow

section, and case 3 (2 foil) with added foil on both

bow and stern section is respectively 31% and 59%

higher than the catamaran without foil These data

show that not all existing catamaran vessels can be

added hydrofoil between the demihulls. To get

optimal hydrofoil-supported catamaran performance,

designing a catamaran ship with hydrofoil from the

preliminary design is necessary. For further research,

a more sophisticated hydrofoil technology is needed

to change the hydrofoil conditions at each ship's

speed. The resulting lift remains stable in providing a

lift to the hull and the least possible drag force.

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