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January 3, 2005, 21:23 
Re: viscous source term

#1 
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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 'builtin' to EARTH. My question is how to activate/deactivate the viscous source term. mt 

February 2, 2005, 06:29 
Re: viscous source term

#2 
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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. 

February 2, 2005, 11:12 
Re: viscous source term

#3 
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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 

February 3, 2005, 03:00 
Re: viscous source term

#4 
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Just a note: deactivating the builtin source term for a specific transport equation actually deactivates ALL the builtin sources for this equation, not just the VISCOUS terms, as was originally asked about.


February 3, 2005, 13:07 
Re: viscous source term

#5 
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Goodpoint Rami,
My understanding is that the built in sources are as below : the pressuregradient 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. 

February 3, 2005, 23:30 
Re: viscous source term

#6 
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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 

February 4, 2005, 08:40 
Re: viscous source term

#7 
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I dont believe there are any sources for the P1 equation controlled by this switch.


February 7, 2005, 00:36 
Re: viscous source term

#8 
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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,....)) 

February 8, 2005, 08:18 
Re: viscous source term

#9 
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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. 

February 8, 2005, 13:24 
Re: viscous source term

#10 
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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 2phase 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 

February 11, 2005, 11:46 
Re: viscous source term

#11 
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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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