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High Viscosity in Two Phase Flow

Posted 30.09.2012, 22:55 GMT-4 Computational Fluid Dynamics (CFD), Microfluidics, Materials, Studies & Solvers Version 4.3a 2 Replies

Cyrus Beh
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Hi,

I have constructed a two-phase flow model, using the "Droplet Breakup in a T-Junction" model in the gallery. I managed to compute the default model successfully. However, when I change the viscosity of the two solutions to a system I am actually interested in (Viscosity phase 1 = 27.64mPa.s, Viscosity phase 2 = 994mPa.s) the model simply does not compute well (time steps are extremely small, making it impractical for solution). I wonder what other parameters in the model I can change to expedite the solution. I am pretty sure that there is something wrong with my model (solver parameters, perhaps?) but I am not very familiar with Comsol. Can anyone give me some suggestions? Thanks!
2 Replies Last Post 24.04.2013, 11:23 GMT-4
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Alex Morgan
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Posted: 1 decade ago 24.04.2013, 10:42 GMT-4
Hi,

I am having exactly the same problem. I'm trying to simulate droplet production in a device that I know does work. I'm using this design to work out how to do simulations in Comsol, so that I can then use the same parameters etc. to do simulations of other designs (before I actually make them). I've changed the densities and viscosities, interfacial tension and contact angle to known values. I get some sort of droplet production initially, but it takes a really long time (2-3days) and after about 75%, the simulation fails.
Does anyone have any advice?

Thanks
Hi, I am having exactly the same problem. I'm trying to simulate droplet production in a device that I know does work. I'm using this design to work out how to do simulations in Comsol, so that I can then use the same parameters etc. to do simulations of other designs (before I actually make them). I've changed the densities and viscosities, interfacial tension and contact angle to known values. I get some sort of droplet production initially, but it takes a really long time (2-3days) and after about 75%, the simulation fails. Does anyone have any advice? Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 24.04.2013, 11:23 GMT-4
Hi

I'm also stuck here: I have (simply) a water droplet falling in air in "phase set" mode:

without the consevative laws on my droplet disolves rapidly (butit solves nicely so long it exist),

with conservative laws on the droplet persist, but rapidly the solver steps comes down to some 1e-18 sec, which is really not usefull when I need some 0.2 sec at least total solver time.

It solves rapidly in "level set", but I cannot use "moving wetting walls" nor "contact physics work options" in "level set", these are only defined in "two flow phase set" method

For those who have some ideas which button to tweak, pls come with your suggestions ;)

--
Good luck
Ivar
Hi I'm also stuck here: I have (simply) a water droplet falling in air in "phase set" mode: without the consevative laws on my droplet disolves rapidly (butit solves nicely so long it exist), with conservative laws on the droplet persist, but rapidly the solver steps comes down to some 1e-18 sec, which is really not usefull when I need some 0.2 sec at least total solver time. It solves rapidly in "level set", but I cannot use "moving wetting walls" nor "contact physics work options" in "level set", these are only defined in "two flow phase set" method For those who have some ideas which button to tweak, pls come with your suggestions ;) -- Good luck Ivar

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