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 Rams December 10, 2002 03:55

wall function

Dear All,

I am using KE-EP turbulence model to simulate a turbulent jet.I would like to set wall conditions through ground due to complex geometry. So could anyone tell me the function/numerical value for co-efficinet(GRND2) and value (GRND2). Here is the example of earth generated wall function.

PATCH(BIW,LWALL,1,80,2,13,1,1,1,1) COVAL(BIW ,U1 , GRND2 , 0.000000E+00) COVAL(BIW ,V1 , GRND2 , 0.000000E+00) COVAL(BIW ,KE , GRND2 , GRND2 ) COVAL(BIW ,EP , GRND2 , GRND2 )

Thanking you Rams

 Olof Liungman December 16, 2002 07:37

Re: wall function

Hello,

unless I've misunderstood something, I don't think you need the actual values of GRND2. Instead, you either replace GRND2 by for example GRND3 (or 4 or 1 or...) and enter your coding at the appropriate place in GROUND (for coefficient and/or value), or you leave the GRND2-setting and code in the appropriate section and chapter for coefficient=GRND2 and value=GRND2.

If your question is exactly what the built-in settings GRND2 result in, then you can find this in POLIS under the entry WALLS.

Hope this helps,

Olof

 Rams December 18, 2002 03:43

Re: wall function

Dear Dr.Olof,

Thanks for your reply. I need to use inlets as well as wall in single patch. In this case, I could not use earth generated wall function. So I would like to make coding for value and coefficient in ground.

I could not find the numerical value or function for coefficient(GRND2) and value(GRND2) in polis.

If possible help me.

Thanking you Rams

 Olof Liungman December 18, 2002 04:26

Re: wall function

Dear Rams,

what version of PHOENICS are you using? If you do not have the latest Polis you can always check out http://www.cham.co.uk/phoenics/d_pol...od/enc_tu8.htm. The GRND2-setting yields the equilibrium log-law functions.

If you need more help I could use some more information about the physical problem you are trying to model. Why do you want a wall and an inlet at the same place?

Regards,

Olof

 Rams December 18, 2002 20:49

Re: wall function

Dear Olof,

Thanks for your reply.I am simulating converging jet in cylindrical polar coordinates. In this model, I used three inlets at the bottom with an interval of 120 degree in x direction. Cross section of the inlet is circular. I used my coding in ground to set inlets. However, the inlets are not exactly circular. Mesh size 80x40x50. If I use earth generated wall function, I need to use many patches. So I would like to set wall as folows.

At z=1 (lwall), I would like to set one patch from y=1 to 40 and x=1 to 80. If there is inlet, phoenics will use my set values in the ground. If there is no inlets, phoenics have to use wall functions. In this case I need to use coding for wall functions in ground as same as inlets. For that I need to know the exact function/value for GRND2 used for u1,v1,Ke and Ep.

Thanking you,

Rams

 Olof Liungman December 19, 2002 04:38

Re: wall function

Hello Rams!

OK, now I think I see your problem. There may be easier ways of doing this that I don't know about, but the info about wall functions you want is available at http://www.cham.co.uk/phoenics/d_pol...d/enc_tu82.htm (the same adress as in my last post). However, I'm not sure GROUND-coding is the easiest way of solving this. It might be easier to create all the required patches in Q1 and do all your coding there (this way you can be sure of getting the correct built-in wall function settings). An interesting alternative is In-Form, which I haven't used but the following help article seems to address your problem: http://www.cham.co.uk/phoenics/d_pol...-form.htm#sour.

If you're still stuck I propose that you create a new thread in this forum with a good title to see if anyone else has a ready-made example. I'm sorry I do not have the time to try to provide you with any actual code, only these hints.

Good luck,

Olof

 Rams December 19, 2002 20:27

Re: wall function

Dear Olof,

Thank you very much for your kind help.

Rams

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