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-   -   flow out of an odd shaped tank (http://www.cfd-online.com/Forums/flow-3d/97231-flow-out-odd-shaped-tank.html)

halfrhovsquared February 13, 2012 01:11

flow out of an odd shaped tank
 
I'm a newbie to Flow3D so forgive me if this is an ignorant question. FWIW I've worked through the tutorials but haven't seen what I'm after.

I want to model an odd shaped draining tank that isn't the typical box, cylinder, or sphere shaped mesh. How can I "inverse" the flow so that the tank is prefilled to a certain level and drains out an odd shaped hole?

JBurnham February 13, 2012 12:25

1) Define the 'hole' of the tank using either simple shapes or an .stl file.
2) Use 'initial conditions' to pre-fill the tank.
3) Use a boundary condition at the outflow of the tank. Use pressure-type if there is back-pressure on the line (either due to friction or due to downstream machinery), or use 'outflow' if the hole freely discharges to atmosphere or void.

halfrhovsquared February 13, 2012 13:24

Quote:

Originally Posted by JBurnham (Post 344161)
1) Define the 'hole' of the tank using either simple shapes or an .stl file.
2) Use 'initial conditions' to pre-fill the tank.
3) Use a boundary condition at the outflow of the tank. Use pressure-type if there is back-pressure on the line (either due to friction or due to downstream machinery), or use 'outflow' if the hole freely discharges to atmosphere or void.

Great, thank you very much, I'll try that.

The "initial condition" confuses me because I'm not sure if it "fills up" the boundary or fills up the "hole". I wish it would let me preview as I assign it. IOW let me "model" the initial condition just like I do with the geometry and boundary condition.

JBurnham February 13, 2012 13:43

Try FAVORizing the initial setup to see the fluid distribution and the resolution of the geometry. It's the button with the eye and the 'F'. If you need more detail (like initial velocities or temperatures) then preprocess the simulation and load the t=0 results.

halfrhovsquared February 13, 2012 18:10

Great advice, I think it's working now and I'm getting a bit more comfortable with the program.

So how do I get the stream to render so that it shoots out into the air/void so that I can see it fall a ways? I tried using another boundary block with no luck. IOW how do I keep from "capping" off my outflow plane that intersects the geometry/void?

Also, is there any difference between using outflow vs specified pressure with a F-fraction of zero?

halfrhovsquared February 14, 2012 12:21

I'm still interested in a better way to model the flow going out into space from the tank.

I was able to get it to work by modeling a box attached to the outflow spigot and making it a hole and then putting a boundary mesh inside so the box goes slightly outside of the boundary. Then make those faces outflow.

Seems like I should be able to do it with just a boundary mesh without having to make the box/hole. That way the box doesn't show up in the rendering (looks bad and is extra work).

Am I missing something?

halfrhovsquared February 15, 2012 19:26

Could someone humor me and tell me how to view the flow out of the end of the tank without creating a "hole" block using solid geometry?

It seems I should be able to add a mesh block to the end of the tank and see the flow but it's eluding me.

Thanks.

halfrhovsquared March 13, 2012 15:33

I find it ironic that this shows up after my recent questions on this forum:

http://www.youtube.com/watch?v=cQQGp...ature=youtu.be

Probably coincidence.

For the record... I have the models working perfectly now with great results.

JBurnham March 13, 2012 15:48

Totally a coincidence. Glad to hear you're up and running.


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