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Microbubbles Injection

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Old   May 13, 2014, 07:52
Default Microbubbles Injection
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Seba
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Hello guys!

I'm new to Star-ccm+ and i have to use it for my thesis in naval engineering.
I'd hope in some advises.

I've to study the possible drag reduction (shear component) obtained by the injection of gas microbubbles (d= 0.05 -1 mm) on a flat plate which is moving in a water flow with free surface.

I've already simulated the case without microbubbles (using the water taxi example as step by step guide) and i've obtained good results (quite similar to experimental ones). So now I've to add microbubbles.. Any suggest?

Can i use a lagrangian phase for bubbles and eulerian phases for air and water flows? I tried but injectors don't work (at least in the volume fraction of water scene nothing seems changed).

As I said I'm very new to the program and I don't know how to begin...I looked for something similar to use as example but no luck..

Bye and Thank you for your time.
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Old   May 13, 2014, 11:52
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If you use lagrangian, your bubbles will not show up in the volume fraction scene because you're using lagrangian. Volume fractions are for eulerian phases. If you want to view the particles you need to add the lagrangian particles to a scene.

How big is the plate? Are you trying to do steady? How big of a machine do you have? I feel that for this you'll probably get a better answer with VOF, but that will be a very expensive calculation.
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Old   May 15, 2014, 04:42
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Quote:
Originally Posted by me3840 View Post
If you use lagrangian, your bubbles will not show up in the volume fraction scene because you're using lagrangian. Volume fractions are for eulerian phases. If you want to view the particles you need to add the lagrangian particles to a scene.

How big is the plate? Are you trying to do steady? How big of a machine do you have? I feel that for this you'll probably get a better answer with VOF, but that will be a very expensive calculation.
The plate is 2500*550*3.. the draft is 384 (mm).

2x cpu X5450 @ 3GHz
ram 22 GB

The attached file is the report of the simulation without bubbles.
How would you implement bubbles?

I thought to use multiphase segregated flow but i need the VOF approach too....and I can't use them simultaneously, can I?

TY
Attached Files
File Type: txt report.txt (29.1 KB, 18 views)
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Old   May 15, 2014, 22:02
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VOF is a multiphase segregated approach. I'm not really sure what you mean.

You don't have much computing power, so VOF is probably not a good option for you. Your best two options are lagrangian or EMP.
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Old   May 16, 2014, 05:48
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Quote:
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VOF is a multiphase segregated approach. I'm not really sure what you mean.

You don't have much computing power, so VOF is probably not a good option for you. Your best two options are lagrangian or EMP.
In the selection of Physics models i can choose VOF OR multiphase segregated flow. It seems i cannot use them simultaneously.
Ok, I'll try with lagrangian.
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Old   May 16, 2014, 12:39
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VOF is a segregated approach. When you select segregated with no VOF, you get EMP.
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Old   October 14, 2014, 08:48
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I am working on the similar grounds.
As far as I have understood I have selected :
1.Multiphase Mixture(Material) which said to be as Eulerian Multiphase
2.VOF(Multiphase Flow Model)
3.VOF Waves(in Optional Models for Water,Air inlet to domain)
4.Lagrangian Multiphase(for air bubble injection).

Is the above model selection appropriate?
I have used injectors & I am able to visualize air bubbles flowing out of the model(after creating appropriate scalar scene & using track file) but I am unable to find any kind of reduction in drag.
I am not really sure if the K-Epsilon turbulence model is really computing for the injected bubbles.

For my 5m model moving at speed of 1.475m/s I have given following parameters for the particle(air):
1.Size as 1mm.
2. Mass flow rate : 6.2E-10 kg/s
3.Velocity magnitude(normal to the hull surfaces): 0.5m/s

Can anyone help me out?
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Old   April 12, 2016, 01:05
Default microbubble drag reduction
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hi!

I AM DOING A SIMILAR KIND OF PROJECT TO FIND DRAG REDUCTION USING MICROBUBBLES ON A RECTANGULAR PLATE BY CFD ANALYSIS. I JUST WANTED TO INQUIRE IF U COULD SEND ME THE RELEVANT PAPERS STATING THE RESULTS AND CFD METHOD USED




Bye and Thank you for your time.
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Old   October 9, 2016, 17:22
Default microbubble modeling wih cfd
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hey guys...does anyone here knows how to model microbubbles in fluent and also gambit?...it is really necessary.
by the way, I mean microbubbles that are used for drug delivery. they have a shell made from lipid or polymer.and a core from gas.the drug is solved in the core. they are also used for ultrasonic imaging from body.
I will be really happy to know the answer as soon as possible.thanks
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