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hamdy January 25, 2011 12:17

Free water jet impinging hot solid surface, including boiling
 
I am working on round water jet that impinges hot surface at 400 deg C. The problem including boiling and wetting front propagation for water. I have the following problems:
  1. The number of phases are 3: air, water and water vapor, or 2: water and water vapor only.
  2. what is the recommended UDF in C format.
  3. How to activate vof model properly in this case
  4. Is there a need to set function hooks
  5. the case is interpreted or compiled
  6. is there any tutorial that may help
Awaiting for your kind help and support. Thanks...

subha_meter July 3, 2012 07:53

If it's still important to you,

- The problem can be treated in both eulerian (air, water) and lagrangian (air, water droplet and water vapor) approach.
- The boiling model available in ansys 13/14 can be used for solid liquid heat transfer. UDF can also be used to model mass transfer phenomena.
- Species transport model will be required to account for vapor phase.
-turbulence model will also need to be incorporated.

Hope it helps,

canev.civelek August 19, 2012 05:28

Hi Subha,

Im hoping you may be able to help with a similar problem.

I need to simulate a water jet into air, i have a simple rectangular domain.

I will be using vof. To set up this problem i have specified velocity inlet of 10ms with volume fraction of water as 1.

I was hoping this would allow the water to be injected into the domain however this is not correct.

Im a little confused how to approch this problem, will i need to create injection of upload a udf to specify the travel of the water.

I thought species transport may work but im still having problems with this.

I hope you can help, Thanks :)

subha_meter August 19, 2012 08:24

Hi Caney,

Are you using a 3D grid? You can use a "velocity inlet" (a small orifice), "wall with slip" around and a "pressure outlet" as outlet boundary condition. A turbulence model will be required. You can use both eulerian-eulerian method and VOF to simulate the phenomena. If you are interested in jet length and shape, any of these approach will do. In either of these two case, you need to supply the velocity magnitude and water volume fraction = 1.0 at the inlet.

You can use DPM spray model to simulate the jet as well if you are interested to know the each droplet's fate. I don't envisage any species transport here if it's a cold jet being sprayed into air.

Regards,





Quote:

Originally Posted by canev.civelek (Post 377670)
Hi Subha,

Im hoping you may be able to help with a similar problem.

I need to simulate a water jet into air, i have a simple rectangular domain.

I will be using vof. To set up this problem i have specified velocity inlet of 10ms with volume fraction of water as 1.

I was hoping this would allow the water to be injected into the domain however this is not correct.

Im a little confused how to approch this problem, will i need to create injection of upload a udf to specify the travel of the water.

I thought species transport may work but im still having problems with this.

I hope you can help, Thanks :)


canev.civelek August 19, 2012 08:46

Hi Subha,

Thanks for the quick response. I am actually trying a 2D to start with.

I have an inlet with velocity magnitude of 10m/s and have specified the volume fraction of water as 1. I also have wall with no slip and pressure outlets.
I have set phase 1 as air and phase 2 as liquid. Is this correct? :confused:

When i run the simulation and check the volume fraction of the phases air and water, the air seems to appear at the pressure outlets. and water seems to be in the whole domain. This is confusing me.

I guess i have to simulate the water through the velocity inlet which for some reason i am not getting correct.

So you have an idea how i can solve this?

Thanks again for your help.
Regards

Sorry forgot to mention i am using vof model with species transport and LES turbulence model.

subha_meter August 19, 2012 19:52

Hi Caney,

I guess you are assigning the entire inlet boundary as "velocity inlet". This would fill the entire domain with water. Only the orifice at the inlet (few mm) needs to be assigned as velocity inlet and you should get a conical shape jet structure. Rest of the inlet boundary can be assigned as "wall with slip". Assign air as continuous phase and water as dispersed phase. No species transport is required. LES model is fine but you need to use a really dense mesh if you wish to resolve the eddies. Hope it helps.


Quote:

Originally Posted by canev.civelek (Post 377688)
Hi Subha,

Thanks for the quick response. I am actually trying a 2D to start with.

I have an inlet with velocity magnitude of 10m/s and have specified the volume fraction of water as 1. I also have wall with no slip and pressure outlets.
I have set phase 1 as air and phase 2 as liquid. Is this correct? :confused:

When i run the simulation and check the volume fraction of the phases air and water, the air seems to appear at the pressure outlets. and water seems to be in the whole domain. This is confusing me.

I guess i have to simulate the water through the velocity inlet which for some reason i am not getting correct.

So you have an idea how i can solve this?

Thanks again for your help.
Regards

Sorry forgot to mention i am using vof model with species transport and LES turbulence model.



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