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-   -   Two Phase simulation (http://www.cfd-online.com/Forums/fluent/33863-two-phase-simulation.html)

 Mansour Al-Harbi June 2, 2004 07:15

Two Phase simulation

Hi all

I am trying to simulate a vissel just like cup with open surface. The water inside is stirred by air. The air is injected from the bottom and should leave the system from the top. Now how can I define the top surface to allow only the second phase (air) to leave the system.

Thanks

Mansour

 welch June 3, 2004 03:40

Re: Two Phase simulation

define the surface as "wall",and then define the boundary condition of it as "escape".

 Mansour Al-Harbi June 4, 2004 06:01

Re: Two Phase simulation (escape boundary)

Thanks roclee

But, the escape boundary condition required the DPM to be activated. However, I am going to use Eulerian two phase model. So is it ok if I run both of them together for the same model. In this case I can have the escape conditions and also the advance two phase model. However, the second phase volume fraction wouldn't exceed 10%.

Thanks

Mansour

 ap June 6, 2004 14:26

Re: Two Phase simulation (escape boundary)

You can simulate your system using velocity inlet for your gas phase and outflow or pressure outlet for outlet.

I don't know the exact configuration of your domain, but you could do something like what's showed in the picture to avoid the water to exit the system:

__________ Outflow BC
|
___________________
| | <--- zone with air
| |
|-------------------| <--- water level
| |
| |
| |
| |
|_______| |_______|
|_____ gas inlet

Hope this helps.

Hi :)

ap

 Mansour Al-Harbi June 10, 2004 08:16

Re: Two Phase simulation (escape boundary)

Hi all

I need to define a second phase sink at the top surface. I know that I need to define a macro. But P dont know how. Could you please give me a guid line to do so.

Thanks

Mansour

 ap June 11, 2004 04:58

Re: Two Phase simulation (escape boundary)

Can you post a link with a sketch of the system you want to model?

You want to model an open vessel, where a liquid is stirred with air and the air leave the system from the top. Is this right? If so, it's not clear why you need to define a sink for the secondary phase using a macro.

Hi :)

ap

 Mansour Al-Harbi June 11, 2004 06:48

Re: Two Phase simulation (escape boundary)

Hi,

Actuly its just like what you discribed. So you think I dont need to create a sink surface. What happened is that when I define the outlet it become active for the mixture then I define it for the second phase. But I am not sure if it is limited for the second phase therefore I want to create a sink.

Thanks

Mansour

 ap June 11, 2004 08:54

Re: Two Phase simulation (escape boundary)

The outlet, as all boundary conditions you define in FLUENT are applied to all the phases you defined in your calculations.

In my opinion you just need to leave a sufficient free (without liquid) space above the liquid, in order to prevent your primary phase to reach the outlet. A similar approach is used in a FLUENT tutorial on heat transfer in a homogeneous fluidized bed, which is reported in FLUENT 6.1 manual.

However, if you want to be certain that your liquid doesn't exit your system, you can define a surface monitor on the outlet monitoring the primary phase volume fraction. You can enable plot to see it better during the simulation.

Hope this help

Hi :)

ap

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