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-   -   Can I add a correlation for turbulent Prandtl No. ? (http://www.cfd-online.com/Forums/phoenics/65441-can-i-add-correlation-turbulent-prandtl-no.html)

ananta June 15, 2009 08:16

Can I add a correlation for turbulent Prandtl No. ?
 
Hi

I am trying to include a correlation to calculate Turbulent Prandtl Number (PRT) in PHOENICS through InForm (gr. 9). The correlation defines PRT as a function of PRANDTL, ENUT and ENUL.

But in the user manual it is mentioned that PRT values can not be set in GROUND (phoenics/d_polis/d_enc/ENC_P.HTM#prt). Does it mean that I cannot include any function for PRT?

Please comment,

Bye

Ananta

phoenics_cfd June 22, 2009 09:41

Variable turbulent Prandtl/Schmidt number
 
A variable turbulent Prandtl/Schmidt numebr can be implemented by setting PRT(PHI) for the variable PHI equal to 1E10; and then using PRNDTL(PHI) to specify either the laminar Prandtl/Schmidt number or laminar diffusivity for PHI so as to include the variable turbulent Prandtl/Schmidt number. Thus, if PRT(C1)=1.E10 and PRNDTL(C1)=GRND, the user can define in Group 9 a laminar Prandtl number equal to ENUL/(ENUL/PRLAM + ENUT/PRTURB) where ENUL and ENUT are the local kinematic laminar and turbulent viscosities, and PRLAM and PRTURB are the local lamianr and turbulent Prandtl/Schmidt numbers. It will be necessary to retrieve the required flow variables out of the PHOENICS F-array, but alternatively the INFORM facility could be used in Group 9 of the Q1 input file.

ananta November 10, 2009 01:30

Thanks for your reply.

As far as I understood from the reply is PRT should be known before I apply your approach. But in my case PRT has to be calculated by PHOENICS as below,


PRT= (0.7*ENUL)/(ENUT*PRNDTL) + 0.85


the above fromula has to be incorporated in PHOENICS and used for turbulent heat transfer calculation.

Please let me know how to incorporate the above formula in PHOENICS.


With best regards

Ananta

phoenics_cfd November 10, 2009 05:35

The turbulent Prandtl number PRTURB (or PRT in your terminology) can be computed directly in a Do Loop in Group 9 of GROUND from any formula that you wish. As explained in my previous post, in order to do this, "it will be necessary to retrieve the required flow variables out of the PHOENICS F-array". Thus, for example, you will need to retrieve the local values of ENUL and ENUT, so as to compute PRT from the formula youi have just quoted.


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