The Study on the Resistance Test Performance of BPPT Mini

Submarine

Erwandi

, Mohammad R. Utina

, Totok T. Murwatono

and Siti Sadiah

Technology Center for Maritime Industrial Engineering, PTRIM BPPT Jl. Hidrodinamika BPPT, Kampus ITS Sukolilo

Surabaya

Indonesian Hydrodynamic Laboratory IHL BPPT Jl. Hidrodinamika BPPT, Kampus ITS Sukolilo Surabaya

Keywords: Submarine, Submerge, Surface, Model, Resistance, CFD

Abstract: This paper describes the study on resistance test performances of Agency for the Assessment and

Application of Technology / Badan Pengkajian dan Penerapan Teknologi (BPPT) mini submarine (midget)

conducted at the towing tank of Indonesian Hydrodynamic Laboratory (IHL) BPPT. Two studies are carried

out to estimate the resistance force of the mini submarine, numerical analysis using Computational Fluid

Dynamics (CFD) and model testing at towing tank. Numerical analysis is employed to evaluate the pressure

and frictional force in the opposite direction of the mini submarine movement. A physical model provided

with the sail and tail is produced at IHL workshop. It has length 3.142 m is made from wood. The model is

towed in two conditions: surface condition and submerged condition in 2 m from the surface. The results

show a good agreement between numerical and experimental.

1 INTRODUCTION

The study on design of Indonesian Mini-Submarine

actually had been started on May 2007 by

Indonesian Navy and IHL BPPT. It was put

emphasis on understanding the hydrodynamic

performance of the submarine. The research on

hydrodynamic performance of submarine is quite

new for IHL. We have many experiences to test the

surface-ship model for more than 23 years.

However, to test of the physical submarine model, of

course, needs special treatment and special

technique. Special strut to hold the model and

special measuring equipment have to be prepared to

test the model submerged 2 meter below surface of

water.

During the design process, CFD analysis is

employed to evaluate the hull form design, the

velocity distribution around the hull, the velocity

distribution around propeller disk (the wake), and

the resistance of mini-submarine.

Since the facility of IHL is built especially to

represent the Froude number similarity, then

conducting the submerged model test of submarine

in towing tank, will trigger controversy. Submarine

that move submerged under water will dominantly

undergo skin friction force. This force should be

investigated in laboratory based-on Reynolds

number similarity. The carriage speed of towing

tank cannot fulfil the speed based on Reynolds

number similarity. Consequently, the submarine

model which is towed in towing tank will experience

much lower Reynolds numbers than the full-scale.

Bettle (2009) proposes to employ the CFD to

cover the disadvantage using lower Reynolds

numbers than the full-scale. Defence Research and

Development Canada as reported by Mackay (2003)

also conducts submarine model test to study the

effect of Reynolds numbers on its performance. He

compares the results of static load measurements in

different facilities using the Standard Submarine

Model, by doing the test in various hydrodynamic

laboratories and wind tunnels in Canada and Europe.

The purpose of this study is to identify the

resistance aspects of BPPT mini-submarine. The

aspects deal with the CFD analysis and resistance

test. Moreover, this study also gives many benefits

to IHL to develop the methods in conducting the

hydrodynamic model testing of submarine using

IHL facilities i.e: towing tank, manoeuvring offshore

basin, and cavitation tunnel (MARIN’s, 2003).

134

Erwandi, ., Utina, M., Murwatono, T. and Sadiah, S.

The Study on the Resistance Test Performance of BPPT Mini Submarine.

DOI: 10.5220/0008549701340138

In Proceedings of the 3rd International Conference on Marine Technology (SENTA 2018), pages 134-138

ISBN: 978-989-758-436-7

2 MATERIALS AND METHODS

2.1 IHL Towing Tank and Measuring

Device

Resistance tests were conducted in IHL towing tank.

It has 250 m length, 11 m width, and 5.5 m depth. It

also provides with towing carriage which speed is in

range 0.2 – 9.0 m/s with ± 0.003 m/s accuracy. The

carriage is moved by four 35 kW electromotors.

Figure 1 shows the IHL towing tank.

A special dynamometer was designed to measure

the resistance of mini-submarine. It can work even

the measuring device is in the submerged condition.

It also provide with special clamp to hold the model

during acceleration and deceleration of the carriage.

When the carriage is in constant speed, the clamp

will be released using pneumatic system and tow

force will be taken over by 25 kg (≈ 250 N) load cell

put in the center of dynamometer.

Figure 1: IHL towing tank and its carriage.

Figure 2: Special dynamometer for measuring resistance

force of submarine model

During tow test it measures the X direction force

parallel to the movement of the model only. The

moments that occur in the test will be omitted by

two-linear bearing put parallel to the longitudinal

axis of the towing tank. Figure 2 shows the photo of

the dynamometer.

The carriage speed and resistance force are

recorded through a Data Acquisition and Analysis

System. The system will amplify the analog signals,

reduce the noises, and convert the analog to digital

data which is fed to computer.

2.2 BPPT Mini-Submarine Model

Table 1 presents the principal dimension of BPPT

mini-submarine. The model was provided with sail,

astern controllable appendages to make

manoeuvring in the horizontal and vertical plane,

and sail plane for forward control surfaces. The

astern appendages for aft control surfaces have X-

plane configuration. However since the test is

resistance only, the astern appendages are not

necessary being moved, thus the appendages fixed to

the hull of the model.

Table 1: Principal dimension of BPPT mini-submarine.

Length Over All (LoA) 22.0

met

Diameter of pressure

hull

3.0

met

Draft 2.6

met

Displacement

submerged

surface

111

133

ton

The physical model for hydrodynamic model test

is manufactured in scale 1 : 7. The model was made

by wood reinforced plastic as recommended by

ITTC. In the sail there is a hole where the strut to

hold the model is connected. As also recommended

by ITTC, the turbulent stimulators are pasted close

to the nose, sail, and appendages to make flow as

turbulent as possible. Figure 3 shows the photo of

the model.

Figure 3: Model of the BPPT mini-submarine.

The Study on the Resistance Test Performance of BPPT Mini Submarine

135

2.3 Model Experiment

For submarine, at submerged mode, Froude equation

cannot be used, because of absence of free surface

effect and wave. Also the use of Reynolds equation

is impossible because model speed will be too large

and and impossible to provide.

(Re)(Re) 

(1)

)/(

V 

(2)

Where: Re is Reynolds number

V is speed (m/s)

L is length (m)

M is abbreviation of model

S is abbreviation of ship (full scale)

Main aid of Reynolds Equation is independent

from turbulent current of model surface. This

turbulent can be provide with several methods such

as making roughness of submarine bow’s. Thus we

can be sure that the current on model is turbulent.

During submerged mode, there are only friction and

viscous pressure resistance there is no wave

resistance.

Thus, the total resistance coefficient CT can be

expressed as follows:

SVPSFST

CCC )()()(



 (3)

Where CF is Frictional Resistance Coefficient

CVP is Viscous Pressure Resistance

Coefficient

Figure 4: Resistance test at 7 knots surface condition (V =

1.361 m/s).

The model was towed in the surface condition

and submerged condition about 2 meters below

water surface. The speed of the carriage was set to

follow the Froude similarity. In the surface

condition, the speed was set to move in the speed

range 0.4 – 2.528 m/s (2 – 13 knots full scale),

whilst in the submerged condition the speed range

was 0.386 – 2.89 m/s (2 – 15 knots full scale).

Figure 5: Resistance test at submerged condition (V =

3.601 m/s).

In the submerged condition, there are two kind

model condition. Firstly, the model provided

turbulent stimulator (TS) was towed. Secondly, it

was towed without turbulent stimulator.

Figure 4 shows the photo when the model was

towed at 1.361 m/s (7 knots) in the surface

condition. Figure 5 is the photo when the model was

towed at 3.601 m/s (7 knots full scale).

2.4 CFD Preprocessing

As comparison to the tow test results, the CFD

analysis was employed to evaluate the shear and

pressure drag (total resistance) of the BPPT mini-

submarine. The commercial CFD code FLUENT

was utilized and the results of the total resistance

were compared with model test. A box related to the

shape of IHL towing tank was made to represent the

computational domain. The BPPT mini-submarine

was put in the center of the computational domain.

The box plane in front of submarine was defined as

velocity inlet boundary condition, the rear plane was

pressure outlet. The top plane is symmetry boundary

condition. Whilst the bottom, left, and right plane

were wall boundary condition. In the surface

condition simulations, a line was made as a

boundary between water and air.

The structured hexahedral volume mesh is

generated around the submarine, as shown in Figure

6 and Figure 7 shows the detail mesh around

submarine model.

The refined mesh was concentrated at hull, astern

appendages, sail, sail plane, and line of water

surface. A very thin prism layer was set at adjacent

to the underlying solid surface. Special treatment

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136

was conducted for simulation in surface condition.

The volumetric mesh refinement was made at free-

surface, bow, near field of wake, far field of wake,

and stern field.

The simulation involved the solving of Reynolds

Average Navier-Stokes equations (Chng et al, 2007).

The k-ε turbulent model is fed to the solver to

simulate the turbulent flow past around submarine

model.

Figure 6: Computational domain of CFD simulation.

Figure 7: Detail mesh around BPPT mini-submarine body.

3 RESULTS AND DISCUSSION

Comparison results of resistance force between

model test and CFD simulation in the surface

condition is shown in Figure 8. It indicates that there

is a good agreement between the result of resistance

test and CFD evaluation. At surface condition there

is a hump and hollow phenomena when the model is

towed around 8 – 10 knots (Froude Number Fn =

0.281 – 0.350). The CFD results are slightly

overestimate comparing with model test results. We

considered that the dynamometer on those speeds

cannot give accurate measurement because the

moment due to the big bow wave is omitted by

linear bearing. Another measurement (not presented

here) using conventional resistance dynamometer,

special for surface ship, gives a good agreement with

CFD simulation in the Froude Number (Fn) around

0.3 – 0.35.

Figure 9 shows the CFD visualization of wave

pattern at 7 knots carriage speed. It gives a good

correlation of the wave pattern shape with model test

as shown in Figure 4.

Figure 8: Result comparisons between model test and CFD

simulation.

Figure 9: Wave pattern of CFD simulation.

The comparison results of the total resistance

force between CFD simulation, model test using

turbulent stimulator, and model test without

turbulent stimulator (TS) in submerged condition are

shown in Fig. 10. There are significant differences

between the model test using TS and without TS,

especially when the model was towed in high speed.

It seemed the differences are caused by the degree of

the turbulence of the flow. If we convert the graph of

Figure 10 to the non-dimensional resistance

coefficient, and also calculate the frictional

resistance using ITTC 57 formula, then we will have

another interesting point of view.

Figure 11 shows the non-dimensional total

resistance coefficients CT of Fig. 10 following the

The Study on the Resistance Test Performance of BPPT Mini Submarine

137

equation (3). We also give the graph of frictional

resistance coefficient CF according to ITTC 57

formula. For CFD simulation there is a fine

correlation between CF and CT. The CT is always

higher than CF. We can say the value between CF

and CT is viscous pressure resistance coefficient

CVP. In CFD simulation CVP increases at high

speed.

Contrary with CFD simulation, at low speed up

to 1 m/s, the total resistance coefficient CT of model

test using TS, is below frictional resistance

coefficient CF. It means that the value of CVP is

negative. It indicates that the flow is laminar. So we

cannot use such kind data for analysis. At speed

more than 1 m/s, the total resistance coefficient

continuously increases when the speed higher and

higher. It seems that the TS gives additional

resistance, comparing to the CFD simulation.

Figure 10: Results of resistance force in submerged

condition.

Figure 11: Resistance coefficient in submerged condition.

The worse situation was also happen when we

conduct the resistance test without TS. It shows that

up to 2 m/s, the flow around the submarine model is

laminar, however more than 2 m/s the total

resistance coefficient has a good agreement with the

CFD simulation.

If we use the CFD simulation as a reference, the

model test in submerged condition needs a fine

tuning of turbulent stimulator. If we put too many

turbulent stimulators, we will obtain higher results

than CFD simulation. If we do not use turbulent

stimulator, it needs higher speed to attain the

turbulent flow.

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