mut and alphat & compressible flow

sasanghomi · September 17, 2013, 07:41

Hi foamers ,

I have a question about setting mut and alphat file in the 0 directory .
I checked rhopimpleFoam tutorial . In this case all values of mut and alphat on the walls are 0 .

type mutwallFunction; ------> for mut
value uniform 0;

type alphatwallFunction; ------> for alphat
value uniform 0;

Also I checked kEpsilon.C in this source code I found a formula for calculating mut and alphat .

mut_ = Cmu_*rho_*sqr(k_)/epsilon_;
alphat_ = mut_/Prt_;

I want to create a case by coldEngineFoam . So I should set mut and alphat file and I am confusing about setting these files.
Please anybody guide me. I should set uniform 0 for them or I should calculate them by using their formula . Why in the tutorial the values have set uniform 0 ??

I appreciate any help from you.
Thanks and best regards,
Sasan.

nimasam · September 17, 2013, 12:54

as much as i know

, when you are using wall function, the value is place holder! so that value is not important and the value of variable will be calculated based upon correlation

sasanghomi · September 17, 2013, 14:42

Dr.Sam
Thank you very much for your reply.

September 17, 2013, 07:41	mut and alphat & compressible flow	#1
sasanghomi Senior Member Sasan Ghomi Join Date: Sep 2012 Location: Denmark Posts: 292 Rep Power: 14	Hi foamers , I have a question about setting mut and alphat file in the 0 directory . I checked rhopimpleFoam tutorial . In this case all values of mut and alphat on the walls are 0 . type mutwallFunction; ------> for mut value uniform 0; type alphatwallFunction; ------> for alphat value uniform 0; Also I checked kEpsilon.C in this source code I found a formula for calculating mut and alphat . *mut_ = Cmu_rho_sqr(k_)/epsilon_;* alphat_ = mut_/Prt_; I want to create a case by coldEngineFoam . So I should set mut and alphat file and I am confusing about setting these files. Please anybody guide me. I should set uniform 0 for them or I should calculate them by using their formula . Why in the tutorial the values have set uniform 0 ?? I appreciate any help from you. Thanks and best regards, Sasan.

September 17, 2013, 12:54		#2
nimasam Senior Member Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,266 Blog Entries: 1 Rep Power: 24	as much as i know , when you are using wall function, the value is place holder! so that value is not important and the value of variable will be calculated based upon correlation Ramzy1990 and joserraw like this. __________________ My Personal Website (http://nimasamkhaniani.ir/) Telegram channel (https://t.me/cfd_foam)

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September 17, 2013, 14:42		#3
sasanghomi Senior Member Sasan Ghomi Join Date: Sep 2012 Location: Denmark Posts: 292 Rep Power: 14	Dr.Sam Thank you very much for your reply.