[trump]

Hello,

I am currently using ANYS CFX to simulate a rotating titanium drum filled with water inside, but I also want that from the (water) internal lateral walls of the drum gas is produced.

So I need to give to the water lateral internal wall surface 2 functions, to be both an interface with the rotating tianium wall and be a (boundary) gas inlet.
But ANSYS CFX doesn't allow to a same surface to be at the same time both interface and boundary.

I wanted then to ask if someone knows how to solve this problem and assign two characteristics to the same surface.

P

[evcelica]

Sounds like something where you could use a boundary source. When you define the wall, there is a tab which says "sources" you would want to add a continuity source here.

[trump]

Thank you very much for your answer Evcelica.
Do you mean that I should then replace the boundary inlet definition with only appliying a continuity source on the water wall surface (which is already used as interface)?

Also it seems to me that when using a continuity source, other than the mass flow I have to impose temperature and other variables values, while I don't want to impose these variables since I would like to see how temperature etc change close to the wall (I hope my explanation is understandable).

Thank you again,

P

[ghorrocks]

If you make the face a wall then you can apply any thermal condition you like. So you don't need to make it a fixed temperature, it could be a heat flux (including adiabatic), convection or some other function. Then apply a continuity source to define the entry of air as Erik suggests.

[trump]

Thank you Glenn and Erik for your help, I managed to solve my problem with you advices.

I have another question though: if I would like instead that the gas appears inside the water, where the heat power beam hit the water (passing through the Titanium wall of the drum), do you think there is a way to simulate this?

Basically an electrons beam hits the drum and goes inside the water also, and because of electrolisis caused by the beam, H2 gas is formed in the water. Now since I didn't know how to simulate this I decided to define a gas inlet at the wall, but the more realistic case would be to produce gas where the beam hits the water.

If you have any tip on how to reproduce this case it'd be very helpful.

Thank you in advance.

P

[ghorrocks]

Define a volume in your mesh and make it a subdomain in CFX-Pre. Then you can apply a mass source term in the subdomain to generate the H2.

[trump]

Thanks Glenn, I will follow your advice.

Do you think though that it is possible to give a rotational law to the gas production in the subdomain? I mean that the H2 gas needs to be produced always at the same spot (where the beam impacts on the wall) while instead the drum is rotating, so this would mean that after one drum tour the gas spot covered all the drum perimeter.

So I was thinking to define the H2 mass with an expression, where I would assign an original starting point x, y, z on the inner wall for the H2 spot and then assign a radial velocity to the H2 spot equal to the drum rotational velocity but in the opposite direction, so that this would results in the H2 mass spot being fixed while the drum rotates.

Do you think this could be a good solution?

Thanks again,

P

[ghorrocks]

You can make the mass source term a function of time, space and just about anything else. You just need to work the function out.

But if you are talking about creating this gas at a range of points throughout the domain you should use source points, not a subdomain. You will have to look into the mass source point options to see what you can do in rotating frames of reference.