experimental analysis of pitching motion in various … · senior researcher at balai pengkajian...

46

International Journal of Mechanical Engineering and Robotics Research Vol. 7, No. 1, January 2018

© 2018 Int. J. Mech. Eng. Rob. Res.doi: 10.18178/ijmerr.7.1.46-50

Experimental Analysis of Pitching Motion in

Various Angle of Attack for Mini Submarine On

Surface Condition

Luhut Tumpal Parulian Sinaga Senior Researcher at Balai Pengkajian dan Penerapan Teknologi (BPPT)

Indonesian Hydrodynamic Laboratory, Surabaya, Indonesia

Email: [email protected]

Abstract— For the operational mini submarine necessary to

analyze pitching motion when it probably to adaptation

from snorkeling to dive condition. Further more, function of

angle of attack is urgently needed. However, slope

adaptation reach optimal as information urgently needed

for navigator guidance. Furthermore, need to be realized for

feasibility study more detail with various angle of attack to

find maximum angel of attack on the mini submarine. This

feasibility study was conducted in MOB Hydrodynamic

Laboratory

Index Terms— mini submarine, slope, physical model test,

MOB

I. INTRODUCTION

Submarine is designed with the main ballast tanks fulls,

the weight of water displaced will be as close as possible

to the weight of the boat, see Fig. 1. That is, there should

be a balance between displacement and buoyancy,

referred to as neutral buoyancy [1], [2]. If true neutral

buoyancy is achieved the boat will float at whatever

depth it presently is, unless something acts on it to make

it rise or sink, see Fig.2. In practice, submariners prefer to

maintain very slight positive buoyancy, so that if power if

lost the boat may be expected to slowly rise to the surface.

Figure 1. Ballast tank submarine

The problem of water sloshing in closed forepeak

ballast. This phenomenon can be described as a free

surface movement of the contained fluid due to sudden

loads [3]. Sloshing is a liquid vibration phenomenon

caused by the movement of the ballast. When the ballast

is in transit, the sloshing would affect stability of the

system severely caused by pitch of angle when submarine

in quick dive cause couple motion [4]. So it is necessary

to minimize the impact of sloshing and avoid large

Manuscript received September 12, 2017; revised January 2, 2018.

amplitude resonance. Sloshing has been studied for many

years by analytical and numerical methods[5,6].

Figure 2. Submersion proccess

In a quick dive, the negative tank is important. By

flooding this tank the boat is made negatively buoyant,

which gets the boat under water quicker. Once submerged,

though, the negative tank is blown “to the mark.” the

submarine to be heavier than the water it displaced while

diving, because you want to get under as quickly as

possible.

The equations of motion for a submarine are similar to

those for a surface ship, however they include all six

degrees of freedom[7]. For a submarine it is normal to

take the origin as the longitudinal center of gravity (LCG),

rather than mid- ships, as this simplifies the equations,

and for a submarine this position is fixed (unlike for a

surface ship)[8]. The axis system used is shown in the

notation. Note that the origin is on the centerline, which

is where the transverse center of gravity is assumed to be.

Positive directions are along the positive axes, and

positive rotations are clockwise as seen from the origin

looking along the positive direction of the axes.

The first approach in the modeling of sloshing liquids

involves using numerical schemes based on linear and/or

non-linear potential flow theory. These type of models

represent extensions of the classical theories by Airy and

Boussinesq for shallow water tanks. Faltinsen [9]

introduced a fictitious term to artificially include the

effect of viscous dissipation. Considering the importance

of nonlinear effects in the sloshing response, Faltinsen [9]

analyzed nonlinear sloshing by perturbation theory.

47


© 2018 Int. J. Mech. Eng. Rob. Res.

Numerical simulation of sloshing waves in a 3-D tank has

been conducted by [10,11].

Two experimentally derived empirical constants were

included to account for the increase in liquid damping

due to breaking waves and the changes in sloshing

frequency, respectively. The attenuation of the waves in

the mathematical model due to the presence of dissipation

devices is also possible through acombination of

experimentally derived drag coefficients of screens to be

used in a numerical model [12].

II. METHODOLOGY

The design model is based on a plan lines obtained

from the owner. From the lines of this plan will be made

for the scale model of the ship. The next stage is to use

the offset table for plotting the results of the previous

scale. After the scale has been determined then in print

and create models. The dimension of submarine as shown

Table I and was designed by computer in Fig. 3.

TABLE I. MAIN DIMENSION SUBMARINES MODEL

Dimension SHIP (m) MODEL (mm)

LOA 22.00 700.00

B Total 4.29 136.30

D Total 5.13 163.30

T 2.60 82.70

dim. Press Hull 3.00 95.50

JR. FS 1.10 35.00

JR. WL 1.00 31.80

JR. BL 0.30 9.50

Scala 31.43

Figure 3. Design littoral submarine

Testing submarine models at even keel condition. It

could be at the time of testing, the condition of the

submarine model trim by bow and trim by stern. The

physical state at the time of testing the other is the lack of

waves. In addition, the volume dispalsemen, the model

and the station to be checked again. Model of submarines

appropriate scale and created a system to regulate ballast

trim of the submarine models. In Fig. 4 shows a model

submarine that has been created.

Figure 4. Littoral submarine model

In this case the force, the left-hand side of the equation,

is the hydrodynamic force acting on the submarine, and

the right-hand side is the rigid body dynamics. This

equation is transformed into body fixed axes, and the

right hand side of the equation is given as follows:

If the origin of the axes is taken at the position of the

longitudinal, and transverse centre of gravity, then both

xG and yG will be equal to zero, simplifying these

equations.

M is the total hydrodynamic pitch moments

respectively. If these hydrodynamic forces and moments

can be determined as functions of time for a motion

submarine. In addition, if the effects of geometry on

these forces and moments are understood then this can be

used to assist in the design of the submarine. the equation

of moment couple motion is given as follows

(2)

(3)

When surfacing. water is retained in the casing, and

other free flood spaces, for a period before it can

escape[13,14]. This will raise the centre of gravity above

that assumed forthe steady state calculations used to

generate Fig. 5. The length of time that this Eater talies

to escape will depend on the size of the free flooding

holes. The large holes may affect the hydro-acoustic

noise generated when submerged[15].

(1)

48



Figure 5. Curve of stability when passing through free surface

A submarine in surfaced condition has to satisfy the

same stability principles as that of a surfaced ship, see Fig.

6. The primary requirement in surfaced condition is that,

it should remain afloat even after any kind of damage.

Which means, there should be a significant volume of the

hull above the waterline. This is called the Reserve of

Buoyancy (ROB). The figure below represents the

volume of the hull that contributes to reserve of buoyancy.

Figure 6. Submarine in submerged and surfaced conditions.

The ROB of a submarine is basically the ratio of the

effective volume of all the MBTs to the volumetric

displacement of the submarine in surfaced condition. The

effective volume is the total “blowable” volume of the

tanks (i.e. volume of the tank required to be filled to

submerge the submarine). And just like surfaced ships,

the surface displacement of the submarine is the weight

of the submarine minus the free flood water. Now note in

Fig. 7, that in submerged condition, the only structure

providing buoyancy is the pressure hull. Hence, the

weight of the submerged submarine minus the free flood

water is equal to the buoyancy on the fully pressure hull.

hull that contributes to reserve of buoyancy.

Figure 7. Volume of Hull contributing to ROB of a submarine.

Submarines are very weight sensitive, as in, during the

entire operation of a submarine, all operations are to be

carried out in such a way so that there is minimum shift

in the longitudinal position of the centre of gravity. As

shown in the figure below, the slightest change in

longitudinal centre of gravity will cause a trimming

moment that results in a drastic decrease in the water

plane area. Since the longitudinal metacentric height will

be proportional to the on the waterplane area, any

trimming moment rapidly reduces the metacentric height.

III. RESULT AND DISCUSSION

In order to exercise the method developed above,

submarine considered. A sketch of the submarine is

shown in Fig. 8 to 10. The Submarine has the following

geometric and mass properties: length = 700 mm,

reference diameter = 163 mm, mass = 4,8 kg

Pitch curves as in Fig. 11. The test results indicate that

the pitch behaviour of the submarine-like body is highly

nonlinear and derivation of a single correlation factor for

all experimental configurations would not be practical.

The closed casing configuration which provides

additional buoyancy and hence a greater restoring

moment. This creates a stiffer system and therefore a

smaller pitch period. The submarine had a pitch period of

about 4, 3 seconds for 5 degrees, 1.4 seconds for 10

degrees and 4.8 seconds for 15 degress.

The primary effect from the smaller period appears to

be a pitch coupling interaction during the first two or

three cycles causing the hump in the decrement curve and

reducing much of the initial roll motion

As part of a validation of the coupled motion and six-

degree-of-freedom method were performed to predict the

flow field, hydrodynamic coefficients, and the motion

paths of submarine at an initial speed = 0 knots. It clearly

shows the orientation of the body at that instant in time

and the resulting flow field due to the body at angle of

attack.

Figure 8. Angle of attack 5 degree


49




Figure 11. Pitch motion

IV. CONCLUSION

A series physical model experiments were carried out

to determine the effects of a free flooding casing on pitch

motions of a submarine operating at the surface. The

goals were to determine whether a free flooding casing

was necessary for a seakeeping model of the submarine,

which would add complexity and expense to the

experiments and if so, how to construct it to best

duplicate the full scale dynamics.

The physical experiments showing little to no change

in pitch damping for the different blockage configurations,

but an increase in pitch damping when going from a large

to a small casing opening size.

The change in position of the centre of gravity that

used in the physical experiments led to an analysis of the

vessel’s pitch period as a function of KG. At the

experimental condition, the pitch period became very

sensitive to any changes in the GM caused either by a

change in the vertical centre of gravity, or the centre of

buoyancy resulting from an open or closed casing[12].

The natural pitchperiod of a vessel is a critical parameter

for seakeeping experiments, as it affects where resonance

occurs in various sea states.

The study concluded that a free flooding casing

physical experiments showed any flow over the top of the

pressure vessel. Extra consideration will also be given to

the model GM and pitch radius of gyration to ensure roll

period is reflective of the full scale vessel.

ACKNOWLEDGMENTS

Further thanks to all co-BPPT Indonesian

Hydrodynamics Laboratories who have been involved in

the testing of submarine Litoral.

REFERENCE

[1] R. K. Burcher and L. J. Rydill, Concepts in Submarine Design, Cambridge University Press, 1995

[2] G. Conte and A. Serrani, “Modelling and simulation of underwater vehicles,” in Proc. the 1996 IEEE International

Symposium on Computer-Aided Control System Design,

Dearborn, Michigan, September, 1996, pp. 62-67. [3] O. F. Rognebakke and O. M. Faltinsen, “Coupling of sloshing

and ship motions,” Jour Ship Research, vol. 47, pp. 208-221, 2003.

[4] J. M. J. Journée, “Liquid cargo and its effect on ship motion,”

in Proc. STAB’97 (Six Internationall Conference on Stability of Ships and Ocean Structures), Varna-Bulgaria, September 22-

27, 1997 , pp. 137-150

[5] X. W. Xiong, Z. B. Wei, C. G. Xiang, “Practical stability of submarine motion under sloshing impacts,” Journal of

Chongqing Jiaotong University(Natural Science), vol. 31, no. 3,

pp. 493-496, 2012. [6] O. M. Faltinsen, O. F. Rognebakke, A. N. Timokha, “Resonant

three dimensional nonlinear sloshing in a square-base basin.

Part 2: Effect of higher modes,” Journal of Fluid Mechanics, vol. 23, no. 5, pp.199-218, 2005.

[7] E. V. Lewis, (ed.), “Principles of naval architecture”, Second Revision. Society of Naval Architects and Marine Engineers

(SNAME), Jersey City, 1988

[8] J. P. Feldman, “State-of-the-art for predicting the hydrodynamic characteristics of submarines,” in Proc. the

Symposium on Control Theory and Naval Applications, pp. 87-127, 1975.

[9] O. M. Faltinsen and O. F. Rognebakke, “Sloshing,” Int. Conf.

on Ship and Shipping Research, NAV, Venice, Italy, 2000. [10] N. E. Mikelis, “Sloshing in partially filled liquid tanks and its

effect on ship motions: Numerical simulations and experimental verification,” RINA Spring meeting, London,

1984.

[11] G. X. Wu, Q. W. Ma, and R. Eatock-Taylor, “Numerical simulation of sloshing waves in a 3D tank based on a finite

element method,” Applied Ocean Research, vol. 20, pp. 337-355, 1998.

[12] P. A. Hsieh, J. D. Bredehoeft, and J. M. Farr, “Determination

of aquifer transmissivity from Earth tide analysis,” Water Resources Research, vol. 23, no. 10, pp. 1824–1832, 1987.

[13] E. D. Hoyt and F. H. Imlay, “The influence of metacentric stability on the dynamic longitudinal stability of a submarine,”

David W. Taylor Model Basin Report C-158, October 1948.

[14] A. B. Phillips, S. R. Turnock, and M. Furlong, “Influence of turbulence closure models on the vortical flow field around a

submarine body undergoing steady drift,” Journal of Marine Science and Technology, vol. 15, no. 3, 2010, pp. 201–217 .

[15] G. Hermanski, “Victoria class submarine: 2D investigation of

free flow phenomenon,” National Research Council of Canada–Institute of Ocean Technology Report TR-2007-12,

April 2007. [16] S. L. Toxopeus, P. Atsavapranee, E. Wolf, S. Daum, R.

Pattenden, R. Widjaja, J. T. Zhang, and A. G. Gerber,

“Collaborative CFD exercise for a submarine in a steady turn,” In Proc. ASME 31st International Conference on Ocean,

Offshore and Artic Engineering, number OMAE2012-83573, Rio de Janeiro, Brazil, July 2012

Luhut Tumpal Parulian Sinaga, was born in Mulberry on April 19, 1957. He currently

works as an employee Agency for the

Assessment & Application of Technology

(BPPT) with the rank of associate researcher

at UPT.BPPH, BPPT, Jl. The complex hydrodynamics Sukolilo ITS Surabaya.

Expertise: Sloshing and Motion of Ship.

50



He has extensive experience in the field of hydrodynamics research mainly related to the field of sloshing. and often involved preformance

government projects in the field of liquid cargo ship to transport eg

FLNG. In addition, the field which he understood was the building structure coast and has been involved in port development projects in

Indonesia.

Dr. Ir. Luhut Tumpal Parulian Sinaga MT, is an active member The Royal Institution of Naval Architects (RINA) headquartered in the UK

and is still active in research in the field of hydrodynamics and

publishing in various countries

experimental analysis of pitching motion in various … · senior researcher at balai pengkajian...

Documents