Experimental and Numerical Study on Slamming Impact

Journal of Ocean Engineering and Technology.
2013.
Feb,
27(1):
1-8

- Received : January 02, 2013
- Accepted : February 14, 2013
- Published : February 28, 2013

Download

PDF

e-PUB

PubReader

PPT

Export by style

Article

Metrics

Cited by

TagCloud

Slamming impact
;
Free fall
;
LM-Guide
;
Air pressure cylinder
;
Boundary element method
;
FLUENT
;
User defined function

1. Introduction

When a ship travels in a rough sea, it frequently experiences various types of impacts from waves. The impact of a ship striking a water surface often causes an extremely large load with high pressure, which shows transient behavior. This can result in substantial damage to the ship's structures. Thus, the water entry problem has attracted much research for its practical importance in the field of naval architecture and ocean engineering (
Korobkin, 1996
;
SNAME, 1993
).
The pioneering work on the water impact problem was done by
von Karman (1929)
. His linearized theory was able to calculate the slamming coefficient successfully. However, his theory was not able to estimate the induced free surface elevation. This limitation was improved by
Wagner (1932)
by taking into account the uprise in the free surface elevation. Mathematical approaches to the water-entry problem were attempted by
Garabedian (1953)
and
Mackie (1969)
. Similarity solutions for wedges with arbitrary deadrise angle were proposed by
Dobrovol'skaya (1969)
. The solution was expressed in the integral equation form which should be solved by numerical computations.
The solution is applicable for any deadrise angle,
2. Development of Boundary Element Method Code

Let us describe the boundary value problem to be solved before we discuss the developed potential code. The present paper deals with a two-dimensional analysis. The z-axis takes the positive direction upward. The
PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

3. Application of Commercial Code

The viscous computation for the water entry problem was carried out using the commercial code FLUENT. The computational domain in FLUENT was discretized into a finite number of tetrahedral cells. The movement of the air-liquid interface was traced by the distribution of the volume fraction of the water in a computational cell. The slamming phenomenon was described by forcing a uniform flow to approach the body. The flow was assumed to be laminar. Any readers interested in FLUENT are referred to the FLUENT web site. Dense meshes were distributed near the body and the free surface around the body surface.
In the case of applying a dynamic mesh, FLUENT uses unstructured meshes in order to reduce the amount of time that is spent to generate meshes, simplify the geometry modeling and mesh generation process, model more-complex geometries than a user can handle with conventional, multi-block structured meshes, and let the user adapt the mesh to resolve the flow-field features.
Once we have determined the important features of the problem we want to solve, the basic procedural steps are as shown below.
- (1)Create the model geometry and grid.
- (2)Start the appropriate solver for 2D modeling.
- (3)Import the grid.
- (4)Check the grid.
- (5)Select the solver formulation.
- (6)Choose the basic equations to be solved: laminar flow is chosen in this computation.
- (7)Specify material properties: air and water-liquid.
- (8)Specify the boundary conditions: wall boundary condition.
- (9)Adjust the solution control parameters.
- (10)Initialize the flow field.
- (11)Calculate a solution.
- (12)Examine the results.
- (13)Save the results.
- (14)If necessary, refine the grid or consider revisions to the numerical or physical model.

PPT Slide

Lager Image

4. Experimental Study

- 4.1 Equipments for Experiments

- 4.1.1 Model

The specimen was a wedge-shaped model. The size of this wedge-shaped model was 29 cm (
PPT Slide

Lager Image

- 4.1.2 Pneumatic Cylinder Test

The pneumatic cylinder could be discharged at 3 m/s. This cylinder was produced by SMC in Japan. The inner diameter is 40 mm, and the shooting range is 100 mm. The inner diameter and shooting range are shown in detail in
Table 1
.
Specifications of instruments for experiment

PPT Slide

Lager Image

- 4.1.3 LM-Guide

The LM-GUIDE was introduced to carry out the free fall test in this experimental research. The LM-GUIDE consists of SBR and SBS. There is a ball-bearing at the inner side of the SBR to reduce the frictional resistance between SBR and SBS. The shape of the LM-GUIDE is shown in
Fig. 4.
PPT Slide

Lager Image

- 4.1.4 Pressure Gauge and Amplifier

The pressure gauge was made by KISTLER in Switzerland. The model number was 701A. The maximum capacity of the gauge was 250 bar, and it was a piezoelectric type. The natural frequency was 70 kHz. The properties of this pressure gauge are given in
Table 2
below. The amplifier was also made by KISTLER in Switzerland. The model number was 5011A, and the specifications are listed in
Table 3
.
Specifications of pressure gauge

PPT Slide

Lager Image

Specifications of amplifier

PPT Slide

Lager Image

- 4.1.5 A/D Convert

An A/D convert was used to convert the analog signal into a digital signal. The existing data were sampled between 60 kHz and 200 kHz, but we attempted to use a 20-MHz converter to more accurately the water-entry impact. This converter was made by ADLINK Technology in Taiwan (Nudak PCI 9812). We determined that there was no significant difference in the data for rates exceeding 5 kHz. Thus all of the experiments were carried out at 100 kHz. The specifications of the A/D converter are shown in
Table 1
.
- 4.1.6 High-speed Camera

A high-speed camera was used to measure the water-entry velocity of the specimens. This was a KODAK SR Ultra-C. The maximum recording rate was 10,000 fps, and total recording time was 1000 fps per 5.5 s. The specifications of this high-speed camera are shown in
Table 1
.
- 4.2 Free Fall Test and Pneumatic Cylinder Test

Fig. 5
shows the front view and side view of the equipment set-up for the free fall tests. The wedge model was fixed to the SBR and fell according to the SBS. The length of SBS was 3 m, which allowed it to fall from a height of 2.5 m. Experiments were attempted at heights of 31.85 cm, 20.38 cm, 11.46 cm, and 5 cm to obtain water-entry velocities of 2.5 m/s, 2.0 m/s, 1.5 m/s, and 1.0 m/s, respectively. The water tank had a box shape. The size of the tank was 1200 × 1200 × 800 (mm), and the material of tank had stainless steel. The tank had an observation window at one side. The free fall test was carried out using 10 degree and 20 degree deadrise angles with water-entry velocities of 2.5 m/s, 2.0 m/s, 1.5 m/s, and 1.0 m/s.
PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

PPT Slide

Lager Image

5. Comparison Between Numerical and Experimental Results

Fig. 9
shows a comparison of the experimental and numerical results. A comparison is shown of the 10 and 20 degree deadrise angles for the experimental results and 10, 20, 30, 45, and 60 degree deadrise angles for the numerical results.
PPT Slide

Lager Image

6. Conclusions

This paper presented the results of two kinds of numerical computations and two kinds of experiments. When it comes to the numerical computation, one represents the potential code and another by viscous one in the numerical computations. The potential code was programmed based on BEM, which is the typical computational tool for a potential problem. The commercial code, FLUENT was utilized to simulate the viscosity and free fall motion. A free fall test is the traditional method used to determine the slamming impact, but we introduced the LM-Guide for an easy and exact test. This pneumatic cylinder test is a new and simple method proposed in the present research.
Ccomparison of conditions

PPT Slide

Lager Image

Acknowledgements

This work was supported for two years by Pusan National University Research Grant.

Arai M.
,
Cheng L.Y.
,
Inoe Y.
1994
A computing method for the analysis of water impact of arbitrary shaped bodies
J. Soc. Naval Arch. Japan
176 -

Armand J.L.
,
Cointe R.
1986
Hydrodynamic impact analysis of a cylinder
Proc. Fifth Int. Offshore Mech. And Arctic Engng. (OMAE). Tokyo, Japan
1
609 -
634

Chuang S.L.
1966
Experiments on flat-bottom slamming
Journal of Ship Research
10 -
17

Cointe R.
,
Miloh T.
1991
Mathematical Approaches in Hydrodynamics
Soc. Ind. Appl. Maths
Philadelphia, USA
Free surface flows close to a surface-piercing body
319 -
334

Dobrovol'skaya Z.N.
1969
On some problems of similarity flow of fluid with a free surface
J. Fluid Mech.
36
(4)
805 -
829
** DOI : 10.1017/S0022112069001996**

Faltinsen O.M.
1990
Sea loads on ships and offshore structures
Cambridge University Press

Fraenkel E.
1991
On the water entry of a wedge. The Mathematics of Nonlinear Systems
SERC Meeting
Bath

Garabedian P.R.
1953
Oblique water entry of a wedge
Commun. Pure Appl. Maths
6
157 -
165
** DOI : 10.1002/cpa.3160060201**

Greenhow M.
1987
Wedge entry into initially calm water
Appl. OceanRes.
9
214 -
223
** DOI : 10.1016/0141-1187(87)90003-4**

Howison S.D.
,
Ockendon J.R.
,
Wilson S.K.
1991
Incompressible water-entry problem at small deadrise
J. Fluid Mech.
222
215 -
230
** DOI : 10.1017/S0022112091001076**

Hughes O.F.
1972
Solution of the wedge entry problem by the numerical conformal mapping
J. Fluid Mech.
56
173 -
192
** DOI : 10.1017/S0022112072002253**

Jung D.J.
,
Park J.S.
,
Kwon S.H.
,
Pack S.W.
,
Jung J.Y.
2002
A note on slamming experiment
Proceedings of the 47th Workshop on Ocean Engineering
55 -
62

Jung D.J.
,
Park J.S.
,
Kwon S.H.
,
Pack S.W.
,
Jung J.Y.
2002
Feasibility study of usage of air pressure cylinder on slamming experiment
Proceedings of the Annual Autumn Meeting, KCORE
229 -
233

Kim B.
,
Shin Y.S.
2003
An efficient numerical method for a solution of two-dimensional hydrodynamic impact problems
Proceedings of the 13th International Offshore and Polar Engineering Conference
HonoluluHawaii
May, 25-30

Korobkin A.A.
,
Pukhnachov V.V.
1988
Initial stage of water impact
Ann. Rev. Fluid Mech.
10
159 -
185

Korobkin A.
,
Okushu M.
1996
Water impact problems in ship hydrodynamics. Advances in Marine Hydrodynamics
323 -
371

Korobkin A.A.
,
Ohkusu M.
1988
Water impact problems in ship hydrodynamics. Ch. 7 in Advances in Marine Hydrodynamics
Computational Mechanics Publications
Southampton, Boston

Kwon S.H.
,
Jung D.J.
,
Park J.S.
,
Pack S.W.
,
Chung J.Y.
2003
An alternative experiment for slamming using an air pressure cylinder
Proceedings of the thirteenth International Offshore and Polar Engineering Conference Honolulu
Hawaii, USA
542 -
548

May A.
,
Baldwin J.L.
,
Walker W.A.
,
Goeller J.E.
1979
Hydro ballistic design handbook. 1, SEAHACTR79-1

Mackie A.G.
1969
The water entry problem
O. J. Mech. Appl. Maths
22
1 -
17
** DOI : 10.1093/qjmam/22.1.1**

Mei X.
,
Liu Y.
,
Yue D.K.P.
1999
On the water impact of general two-dimensional sections
Applied Ocean Research
21
1 -
15
** DOI : 10.1016/S0141-1187(98)00034-0**

1993
Notes on ship slamming
The Society of Naval Architects and Marine Engineers

Takemoto H.
1984
Some considerations on water impact pressure
J. Soc. Navel Arch. Japan
156
314 -
322

Von Karman T.
1929
The impact on sea plane floats during landing. NACA Technical Note 321

Wagner H.
1932
Über stoss-und gleitvergänge an der ober fläche von flussigkeiten
Z. Angew. Math.
12
(4)
193 -
215
** DOI : 10.1002/zamm.19320120402**

Watanabe T.
1986
Analytical expression of hydrodynamic impact pressure by matched asymtotic expansion technique
Trans. West-Japan Soc. Naval Arch.
71
77 -
85

Yamamoto Y.
,
Ohtsubo H.
,
Kohno Y.
1984
Water impact of wedge model
J. Soc. Naval Arch. Japan
155
236 -
245

Zhao R.
,
Faltinsen O.
1993
Water entry of two-dimensional bodies
J. Fluid Mech.
246
593 -
612
** DOI : 10.1017/S002211209300028X**

Zhao R.
,
Faltinsen O.M.
,
Aarsnes J.V.
1996
Water entry of arbitrary two-dimensional sections with and without flow separation
Proceedings 21st Symposium on Naval Hydrodynamics
Trondheim, Norway
408 -
423

Citing 'Experimental and Numerical Study on Slamming Impact
'

@article{ HOGHC7_2013_v27n1_1}
,title={Experimental and Numerical Study on Slamming Impact}
,volume={1}
, url={http://dx.doi.org/10.5574/KSOE.2013.27.1.001}, DOI={10.5574/KSOE.2013.27.1.001}
, number= {1}
, journal={Journal of Ocean Engineering and Technology}
, publisher={Korean Society of Ocean Engineers}
, author={Kwon, Sun Hong
and
Yang, Young Jun
and
Lee, Hee Sung}
, year={2013}
, month={Feb}