[mariconeagles96]

Dear All,

Are there anyone here familiar with this theory - hydrophobic surfaces ? and if CFX can do this job? Maybe a simple model like a wall surface with hydrophobic characteristics and applying water to pour into it (small amount) and see what happens. Thanks! =)

[ghorrocks]

Yes, CFX can model wall boundaries with large contact angles. I have done years of modelling with hydrophilic/hydrophobic surfaces.

But be careful about grid convergence - you will probably find it is not possible to achieve. This will limit the accuracy of the results using wall contact angles.

[mariconeagles96]

thanks @ghorrocks for your usual response.

anyway, since I am new to this field and kind of exploring this how do i start it with? is this a multiphase flow (laminar or turb depending on my research but i guess i have to start with laminar first), a volume fraction? and assuming the model is very thin about 30microns or so... what should be the domain flow proportion? Or are there simple approaches to just get me started first and then will move on to a much detailed model. thanks!

[ghorrocks]

The decision of laminar or turbulent should be pretty easy - just work out a typical Reynolds number and see if you are in the turbulent regime. For most surface tension flows you are in low Re number flows so the flow is laminar, but you need to check this in your case.

Some really good validation cases for surface tension driven flow are:
* spherical drop - see if you can get the correct laplacian pressure in the drop.
* drop on a plate with various contact angles - see if you get the pressure right again.
* capillary driven flow in a thin tube - there is an analytical solution for this so it makes an excellent benchmark. And you will find for yourself that you can be close, but never exact due to the moving contact line issue I mentioned in post #2.

[lisa]

Hi ghorrocks, I am also trying to do a hydrophobic/hydrophilic simulation using CFX any documents that is shareable for me to have a look on the properties and steps needed. Thanks.

[ghorrocks]

I do not know of any tutorials or documents on this, other than the CFX documentation. If you ask ANSYS support they might have something.

I recommend attempting to model the benchmark cases I list in post #4, as when you can model those well you know you understand the surface tension model. Particularly if you understand why getting mesh-independant, accurate results in a capillary tube is impossible

[lisa]

Thanks a lot will check with them.

[FORGODSAKE]

I am working on fluif flow in superhydrophobic microchannels .but i am not able to make geometry of it. please can anyone help me with this.thankyou

[ghorrocks]

Do the tutorials available on the ANSYS Academic website (if you are an academic user) or Customer site (if you are a commercial user). Then you will understand how to use it.

If this does not answer your question then refer to this FAQ: https://www.cfd-online.com/Wiki/Ansy...ible_answer.3F

And this post: Before you post a question please read this