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Old   January 3, 2005, 21:23
Default Re: viscous source term
  #1
mt
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Hello all

In PHOENICS, boundary conditions and sources appear on the r.h.s. of the differential equation for a variable phi.

these conventionally recognised source terms, such as pressure gradients or viscous heating terms, are 'built-in' to EARTH.

My question is how to activate/deactivate the viscous source term.

mt
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Old   February 2, 2005, 06:29
Default Re: viscous source term
  #2
Mick Hughes
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The built in sources are activated/deavtivated through the TERMS command in the Q1, the first argument should be toggled to N.

From the VR menu, choose "MOdels" then "Solution Control", then the "TERMS 1 SOUR" should be toggled to N for the rlevant variable.

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Old   February 2, 2005, 11:12
Default Re: viscous source term
  #3
tah
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Dear Mick,

Thank you for your reply. I wonder if this is only valid for the pressure term source? ( What kind of term source are activated/deactivated by this manner)

regards,

tah
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Old   February 3, 2005, 03:00
Default Re: viscous source term
  #4
Rami
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Just a note: deactivating the built-in source term for a specific transport equation actually deactivates ALL the built-in sources for this equation, not just the VISCOUS terms, as was originally asked about.
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Old   February 3, 2005, 13:07
Default Re: viscous source term
  #5
Mick Hughes
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Goodpoint Rami,

My understanding is that the built in sources are as below :

the pressure-gradient source for velocity; the centrifugal and Coriolis source for velocity (polar cartes=F); the DPDt term in the energy equation the dissipation of mechanical energy into heat in the energy equation.

By viscous term, I assume that one means this last term on the list (viscous heating). In which case I would remove all the built in sources and add the DPDt source myself with a patch/coval if it was required.

However as the default is to solve for TOTAL Temp then its not included anyway, so removing all the built in sources would do the job

If by viscous term one means the diffusion term, then this can be removed through the TERMS command also.

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Old   February 3, 2005, 23:30
Default Re: viscous source term
  #6
tah
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thank you Rami

I want to know what is the exact meaning of the built in source term for P1.

( is it from continuity equation ? )

regards,

tah
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Old   February 4, 2005, 08:40
Default Re: viscous source term
  #7
Mick Hughes
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I dont believe there are any sources for the P1 equation controlled by this switch.
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Old   February 7, 2005, 00:36
Default Re: viscous source term
  #8
tah
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Theorecally in FVM there is no source term for the P1 variable. so, what is the diffrence when TERMS 1 SOUR is toggled to N/Y for P1.

( terms (P1, Y, ....) and terms (P1, N,....))

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Old   February 8, 2005, 08:18
Default Re: viscous source term
  #9
Mick Hughes
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I dont know, why dont you try toggling on/off and see.

I just did and .. as far as I can tell there is no difference in the solution so I am confident there are NO sources for P1.

But from a software development viewpoint, do you expect P1 to not have a TERMS(N/Y option and be different from most other variables.

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Old   February 8, 2005, 13:24
Default Re: viscous source term
  #10
Mick Hughes
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Hi tah,

I have asked some colleagues and have some extra info which may be of interest.

The are some extra terms to the P1, these are for 2-phase flows :

1/ interphase mass transfer 2/ phase diffusion

but 1/ is specified through "mdot" and 2/ is automatically included.

Additionally with the the diffusion term, only the d/dx (gamma d/dx) "shearing" terms are added not the d/dx(gamma d/dy) type terms......(hope that makes sense)

but none of the above through TERMS..

regards

mick

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Old   February 11, 2005, 11:46
Default Re: viscous source term
  #11
tah
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Hi Mick,

thank you for your explanation. they were very useful for me. I understand that in the case of single flow phase, terms(P1, N/Y,....) is irrelevant.

tah
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