Multiphysics2009, 9-11 Dec., 2009 Kumamoto Industrial Research Institute Behavior of bubble pulse in...

Multiphysics2009,　 9-11 Dec., 2009

Kumamoto Industrial Research Institute

Behavior of bubble pulsein food processing

using underwater shock wave

Hideki Hamashima*, Manabu Shibuta**, Yosuke Nishimura**, Shigeru Itoh**

*Kumamoto Industrial Research Institute**Shock Wave and Condensed Matter Research Center, Kumamoto University

2Multiphysics2009,　 9-11 Dec., 2009


Content

Background and Purpose

Experiment

Numerical simulation

Conclusion



Background (1/2)

Explosive processing

Explosive forming, Explosive welding, Explosive synthesis,Explosive cutting(Shaped charge) etc.

Recent years…Recent years…

Shock processing of Apple

Apple subjected to shock load

Conventional Techniques for Explosive and Shock wave …

(Except for Destruction technique!)

Food processing

Explosive and Shock wave are used for

If the apple with the load of the shock wave is extracted by hand, fruit juice will overflow. Fruit juice can be very directly drunk for a straw to an apple.



Background (2/2)

Apple subjected to shock load

Food processing using shock wave

New Food Processing!New Food Processing!

Shock wave is generated from the explosion of explosiveand pulse power of a high voltage.

Attract attention!Attract attention!

Excellent Features!Excellent Features!• Processing time is very short.• There is little influence of heat to food.• Deterioration of food does not take place easily. • Bactericidal effect etc.

However…However…The details of shock processing are not clarifiednot clarified.

The shock wave which processes food has

•Shock wave generated by early explosion

•Shock wave generated by expansion contraction of detonation product gas(Bubble pulse).



Purpose

Development of Food processing device using shock waveFinal Goal!Final Goal!

Therefore…Therefore…

In this research,

•Shock wave generated by early explosion

•Shock wave generated by expansion contraction of detonation product gas(Bubble pulse). InvestigationInvestigation

!!fundamental investigation

・ Optical observation using a high-speed video camera

・ Numerical simulation

Research method

In order to investigate the behavior of Bubble pulse,



Bubble Pulse

• There are shock wave and explosion product gas in the fundamental phenomenon of underwater explosion. A gas bubble shows the complicated action which repeats expansion and contraction. The pressure called a Bubble pulse occurs at the time of contraction (when becoming the minimum radius).

• Although the maximum pressure of a bubble pulse is small compared with a shock wave, there is the feature that duration of shock is long. It is considered that it is important when calculating the shock response of marine structures, such as a ship.



ExperimentExperiment



Experimental Setup

Water ContainerWidth : 1.2mLength : 3.2mDepth : 1.8m

High-speedVideo Camera

ExplosiveBubble

Pressure Gauge

WaterWater is poured fromthe bottom to 1.6m.

Observation Window

1.2m

3.2m

1.8m



Experimental Water Container

Water ContainerWidth : 1.2mLength : 3.2mDepth : 1.8m

Water is poured from the bottom to 1.6m.

High-speed Video Camera

Phantom 　 V7.3Vision Research, Inc.Resolution : 800x600 pix Rates : 2000fps



Experimental Condition

Explosive Depth of Water (mm)

ED 200

ED 300

ED 400ED : No.6 Electrical Detonator

High-speedVideo Camera

Depth

Explosive

Water

Observation Window

1.6m



Experimental ResultsExperimental Results



Movie (ED, Water Depth:200mm,300mm)

200mm 300mm

These are movies at 200mm and 300mm in depth of the explosive.Detonation product gas repeated the expansion contraction like this.In the both experiments, the bubble at the first cycle expanded and contracted spherically. However, the bubble at the 2nd and 3rd cycle didn’t become spherical.



Movie (ED, Water Depth:400mm)

400mm

This is a movie at 400mm in depth of the explosive.Detonation product gas similarly repeated the expansion contraction as for this.



Bubble Diameter (Experiment)

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ED(200mm:EXP)ED(300mm:EXP)ED(400mm:EXP)

This is a time change of the bubble diameter obtained from the movies ahead.All experiments had the same diameters of the bubble for the first cycle.The bubble diameter became small by attenuation as the cycle progressed. And it became small at the 2nd cycle as depth of explosive became deep.



Fall of Bubble (Experiment)

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ED(200mm:EXP)ED(300mm:EXP)ED(400mm:EXP)

This is figure where the amount of the fall displacement of the bubble was shown. The amount of the fall displacement of the bubble has decreased as the position of explosion becomes deep.



Fall of Bubble (ED:200mm:Experiment)

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Bub

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Bub

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DiameterDisplacement

Fall of BubbleThis is figure where the bubble diameter and the amount of fall of the bubble were shown. This is a result at 200mm. The bubble fell intensely when the bubble contracted.



Fall of Bubble (ED:Experiment)

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Bub

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Bub

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250

300Bub

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Dis

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ED:200mm ED:300mm

ED:400mm

Fall of Bubble

The bubble fell intensely when the bubble contracted at all the experiments.



Consideration of Fall of Bubble

(a)Expansion (b)Contraction

(a) In a expansion process, the gas bag near a rigid body wall expands to the position of a dotted line.

(b) In a contraction process, water does not return from the circumference uniformly. Water follows the streamline at which it turned from the wall side, and the side which does not have a wall is easier to return.



Consideration of Fall of Bubble

It is considered that a big flow of water is generated because it is easy to move in water on explosive below, and the bubble fell in these experiments.

Water

Air

Gas

Contraction

Fall of bubbleFall of bubble!!



Pressure History (ED:300mm)

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Bu

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r (m

m) Diameter

Displacement

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0 10 20 30 40 50 60 70 80 90 100Time(ms)

Pre

ssu

re(M

Pa) Pressure Measurement

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This is a pressure measurement result obtained from a past experiment.After the bubble contracted, the shock wave has been generated.



Pressure History (ED:300mm)

23.5ms0.5ms

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6

8

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0 10 20 30 40 50 60 70 80 90 100Time(ms)

Pre

ssu

re(M

Pa) Pressure Measurement

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42.0ms 11.5ms0.0ms

When a shock wave reache ｄan observation window Usual framing photographs

In an optical observation, it was understood that the shock wave reached the window from whitening of the window.



SimulationSimulation



Simulation Model

Simulation was performed using LS-DYNA (SMP Edition ;smp971 ） .

Quarter model Simplification!

100mm

900mm

500mm500mm

400mm

Air

Water

Explosive1000mm

500mm

400mm

Air

Explosive

Water

Z

X



Calculation Method

Calculation method

Burn technique

Euler method: Explosive, Air, Water

CJ volume burn + Programmed burn

(point ignition)

Mesh size

Euler element : 10 x 10 x 10 (mm)

Number of elements

Euler element : 250,000



Equation of States (EOS)

Calculation method

Euler method: Explosive, Air, Water

Explosive

Detonation Products EOS: JWL EOS0.6g SEP was used instead of ED.

Air

Density: 1.252kg/m3

EOS: Ideal gas EOS

Water

Density: 1000kg/m3

EOS: Gruneisen EOS



Calculation ResultsCalculation Results




This is a numerical result when the position of the explosive is 200mm in depth.Although the bubble of the first cycle spread spherically, the bubble of the 2nd and 3rd cycle burst.




This is a numerical result in case the position of the explosive is 300mm in depth.Only the bubble of the first cycle carried out expansion contraction spherically like the case of 200mm.




This is a numerical result in 400mm. It differed in 200mm and 300mm, and the bubble of the 2nd and 3rd cycle was able to be expressed.



Bubble Diameter (Calculation)

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ED(200mm:CAL)ED(300mm:CAL)ED(400mm:CAL)

This is a time history of the bubble diameter obtained from the numerical result. In the three condition, the outside diameter of the bubble at the first cycle became the same size as about 280mm.



Fall of Bubble (Calculation)

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ED(200mm:CAL)ED(300mm:CAL)ED(400mm:CAL)

This figure is shown about the fall of the bubble.An intense fall was not obtained too much like this.



Fall of Bubble (ED:200mm:Calculation)

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This is figure where the bubble diameter and the amount of fall of the bubble obtained from numerical analysis were shown. This is a result at 200mm. The bubble when the bubble contracted has not fallen intensely compare with the case of the experiment.



Fall of Bubble (ED:Calculation)

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ub

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ED:200mm

ED:400mm

ED:300mm

No Fall of Bubble

Thus, at all the simulations, an intense fall of the bubble like the experiment was not obtained when the bubble contracted.



Comparison between Comparison between Experimental and Calculation Experimental and Calculation

ResultsResults



Comparison of Bubble Diameter (ED200mm)

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ED(200mm:EXP)ED(200mm:CAL)

This is a comparison of the experimental result and the numerical result at 200mm and 300mm in depth.The histories at the first cycle was almost corresponding.

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200mm 300mm



Comparison of Bubble Diameter (ED400mm)

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This is a comparison at 400mm in depth of the explosive. The bubble history at the first cycle was almost corresponding. The bubble outside diameter of the numerical result did not attenuate compared with the experiment result. Moreover, the analysis repeated the expansion contraction at a slightly short cycle.



Comparison of Fall of Bubble

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ED(200mm:EXP)ED(300mm:EXP)ED(400mm:EXP)ED(200mm:CAL)ED(300mm:CAL)ED(400mm:CAL)

This is figure where the falls of the bubble were compared.The analysis was small the bubble fall. It is considered that this is because the condition of the analysis was an analysis in the infinite waters.



Comparison of Pressure History (ED:300mm)

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Pre

ssu

re(M

Pa) Experiment

Calculation

-10 0 10 20 30 40 50 60 70 80 90

1st PulseEXP: 8.1 (MPa)CAL: 8.7 (MPa)

This is a comparison of the pressure histories at 300mm. The peak value of an initial shock wave hardly changed. However, the time that reached the gauge at the analysis became early. It is considered that this appeared by the difference between the infinite waters and the limited waters, too.



Conclusion

・ It succeeded in the high-speed photography of the bubble within a limited container. The data of the variation with time of the maximum diameter of a bubble or the cycle of a bubble pulse was able to be obtained.

・ It turned out that the maximum bubble diameter becomes small by attenuation as the cycle progressed.

・ In the underwater explosion near the water surface, it demonstrated that involved in and a high-speed flow was made to the bottom. The fall phenomenon of the bubble has been confirmed.

・ Also in the numerical simulation, it could be simulated about the reduction of the maximum bubble diameter and the fall phenomenon of the bubble.



Future Work

・ The simulation that models even the water container is conducted. Whether the amount of fall of the bubble becomes larger when an analytical model with limited waters is used is investigated.

・ The simulation of a Bubble pulse is conducted by more fine mesh. We constructed a parallel computer recently.



Thank you for your attention.Thank you for your attention.

Multiphysics2009, 9-11 Dec., 2009 Kumamoto Industrial Research Institute Behavior of bubble pulse in...

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