Learning Forum

[elisio]

Hi,

 

I am simulating an air flow through a furnace and i have set my Outlet as Pressure-Outlet:

The red region is my outlet.

I dont want air entering my outlet region so i selected Prevent Reverse Flow, is it right?

 

I'd like to know more about these options:

- Backflow Reference Frame: Absolute or Relative to Adjacent Cell Zone?

- Backflow Pressure Specification: Total Pressure or Static Pressure?

 

And What will the Backflow Total Temperature interfere?

 

Thanks.

[Keyur Kanade]

reverse flow occurs when there is pressure gradient in opposite direction and flow wants to re-enter the domain. 

usually this is attributed to wrong location of outlet. 

if you are getting any reverse flow, from image you have provided, i would say extend outlet so that you dont get any reverse flow. 

fluent uses reference values for reference specifications. 

please see help manual. 

/forum/forums/topic/how-to-access-the-ansys-online-help/

[elisio]

Hi kknade,

This was my first simulation:

So, I have already extended my outlet a little bit, should i make it more? If yes, how much do you think is enough to have good results at the outlet region of the picture above? (The unique problem i face is the 512k cells student limit)

 

Anyway, why the Reverse Flow Prevetion option shouldn't be set here? Thanks

Thanks for your review.

 

 

[Rob]

In this case reverse flow is due to the geometry, ie the change in flow direction. If you're looking at the flow around the lower ports you can ignore it. If you're looking at the flow higher up the domain it could be important so I'd extend the outlet by about the same again. 

For the cell limits, if you decompose the domain you can hex (or sweep tri cells) for a fair amount of the volume. That should drop the cell count by a factor of 4-5. 

[elisio]

Ok i'll try it!

And what about the Backflow Total temperature ? Does it interfere something?

 

Thanks a lot