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-   -   how to change boundary type in unsteay calculation (http://www.cfd-online.com/Forums/fluent/29218-how-change-boundary-type-unsteay-calculation.html)

cfdfans January 7, 2002 03:01

how to change boundary type in unsteay calculation
 
How to change boundary type in unsteay calculation? when T=t0 ,I set boundary condition as WALL and begin calculate. when T=t1, I want to change the boundary condition as interior . How to get it with UDF of fluent.

thanks

Jin-Wook LEE January 7, 2002 07:18

Re: how to change boundary type in unsteay calcula
 
I think that 'WALL' can't(and shoudn't) be changed to 'INTERIOR' in CFD(including Fluent) calculation.

CFD is basically BVP(Boundary Value Problem). 'WALL' means boundary. So, how can BOUNDARY be changed to INTERIOR ?

Sincerely, Jinwook


Ashutosh January 7, 2002 11:06

Re: how to change boundary type in unsteay calcula
 
I think interior in Fluent means same material both sides, otherwise it has to be a wall.

cfdfans January 7, 2002 22:34

Re: how to change boundary type in unsteay calcula
 
In my problem ,chamber have a valve .when T=t0 the valve is close, T=t1 the valve is open. how can i simulate this process.

Jin-Wook LEE January 8, 2002 05:05

Re: how to change boundary type in unsteay calcula
 
I think that your problem is IVP(Initial Value Problem). From the T=t0 to T=t1, there is no flow because the valve is closed. Then, I guess that your interest should be focused on the flow field from T=t1.

Then, generated the mesh without valve if valve is entirely removed from the chamber. Or generate the mesh including the valve for open position if the valve is still in the chamber, and let it as 'SOLID'.

And, finaly you can simulate the flow field from the T=t1 with initial condition of 'REST' everywhere.

Sincerely, Jinwook


Bipin January 9, 2002 09:16

Re: how to change boundary type in unsteay calcula
 
Hi,

The interior can be declared as wall. Fluent in this case create a wall shadow.

The better way for you would be define an interface between two surfaces. This will allow the flow of fluid across the zones.

If you dont want to allow the flow across this zones at time t1 (N time step)

go to solve--->Execute Command

Enter the time step corresponding to required time.

Enter the text command as /define/grid-interfaces/delete "interface-name"

This will delete the interface and would not allow the flow.

Hope this helps

Bipin


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