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kestasposkus September 23, 2011 16:45

interface problem
 
2 Attachment(s)
Hello,

I have problem with mesh inter face:
If I do not set Inflation in the moving interface part interface works, but my y+ is terrible more then 1000....
if I set Interface the solver do not solve and stop with error.

So my question is how to set interface witch can convergent.

Or, if in the part, which is in my solution is only pressure generator, can be very big y+ >1000. Is it will have affect on my interesting zone marked color black?
it means for pressure or velocity numbers?

Vyc

ghorrocks September 24, 2011 07:33

Sorry, I do not understand your question, and your images are too small to be useful.

Whether y+>1000 is a problem or not depends on your simulation. If the boundary layers do not significantly contribute to the result then this is fine. If boundary layers do significantly contribute then you almost certainly need to improve the near wall mesh.

kestasposkus September 28, 2011 04:48

1 Attachment(s)
hello, ghorrocks

thank You for replay

I put new figure with my problem


I have problem with mesh inter face:
If I do not set Inflation in the moving interface part interface works, but my y+ is terrible more then 1000....
if I set Interface, the solver do not solve, and stop with error.

So my question is how to set inflation witch can convergent with moving mesh.

Or if I leave moving interface parts (red color) with y+ more then 1000, pressure and velocity results will be accurate at the static inter face zone (black color)?

Vyc

ghorrocks September 28, 2011 08:21

If you are modelling a valve cracking open with a large pressure behind it I think you will find that boundary layer resolution is of secondary importance. In this case your large y+ would not be a problem (but you will probably have to refine the mesh anyway).

kestasposkus September 28, 2011 12:30

Hello, ghorrocks,

thank You for replay

Yes You are right it is valve opening problem sorry that I do not mentioned.
I want to solve it in that way: set pressure and temperature in the cylinder just before opening outlet window.
And then it opens I shall get right pressure and velocity numbers.
But if I set these parameters as initial in cylinder zone, rapidly vanish before opening outlet window.

Question: how set pressure and temperature in cylinder ?

ghorrocks September 28, 2011 21:07

Quote:

how set pressure and temperature in cylinder ?
With initial and boundary conditions.

Quote:

And then it opens I shall get right pressure and velocity numbers.
That is CFD nirvana.

kestasposkus September 30, 2011 04:24

3 Attachment(s)
hello, ghorrocks

thank You for replay

I still have problem with pressure set ups in the first picture I set initial pressure
in the second picture from results file I can see higher pressure 0,2MPa in the cylinder and 0Pa in muffler
but in the third picture after very short time pressure start drop up to 10time lower and in the muffler I got negative pressure ? when intersection still not overlap
why? it should stay constant cylinder only move not deforming (cylinder volume constant)

I think that initialization should be set some how different

thanks for any suggests

vyc

ghorrocks October 3, 2011 18:49

You have a problem with your initial conditions and/or boundary conditions.


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