CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

nut and nuTilda in simpleFoam

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   August 7, 2014, 15:02
Default nut and nuTilda in simpleFoam
  #1
Member
 
Michael Kruger
Join Date: Jul 2014
Location: South Africa
Posts: 37
Rep Power: 3
mich_K is on a distinguished road
What are the differences between nut and nuTilda in the simpleFoam solver?

In the PitzDaily simpleFoam tutorial, both nut and nuTilda are set to zero, does this mean the problem is modelled as inviscid?

In the airFoil2D tutorial both nut and nuTilda are given values of 0.14 m^2/s.

I believe the kinematic viscosity of air at room temp is about 15.11e-6 m^2/s, where in the world does the value of 0.14 m^2/s come from?? Is it perhaps because of a scaling factor introduced somewhere?

Any clarification on the subject will be greatly appreciated.

Thank you in advance.
mich_K is offline   Reply With Quote

Old   August 8, 2014, 03:33
Default
  #2
Senior Member
 
RodriguezFatz's Avatar
 
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,097
Rep Power: 16
RodriguezFatz will become famous soon enough
Hi Michael,

The files you are refering to provide boundary and initial values for the turbulent viscosity. (That's why it is "nut" and not just "nu"). Depending on the turbulence model you use they have different names. I don't know the airFoil2D tutorial, so I don't know which turbulence model it uses and thus which of the files is actualy needed. The fastes way is just to delete both files and start the solver. It will tell you the name of the files that are needed to run.
"Nutilda" comes from the Spalart-Allmaras model, where "nut" is transformed to "nuTilda" and the model equation is solved for nuTilda.
Anyway, if you set the value to zero in these files it just means that the initial value is zero. If you don't get convergence you can try other values, such as "0.14m^2/s" in the tutorial.
The viscosity of air is set in a different file (constant/transportProperties) and should match the value you wrote.

Philipp.
__________________
The skeleton ran out of shampoo in the shower.
RodriguezFatz is offline   Reply With Quote

Old   August 8, 2014, 03:38
Default
  #3
Member
 
Michael Kruger
Join Date: Jul 2014
Location: South Africa
Posts: 37
Rep Power: 3
mich_K is on a distinguished road
Excellent thank you Phillipp, that solves my problem.

Might you be able to help be with this question: Running a solver from a case directory stored anywhere?

Thank you in advance.
__________________
-------------------------------------------------------
Michael
mich_K is offline   Reply With Quote

Reply

Tags
nut nutilda, simplefoam, solvers

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
nut and nuTilda phile OpenFOAM Running, Solving & CFD 26 January 4, 2015 21:54
nut and nuTilda in simpleFoam mich_K OpenFOAM Running, Solving & CFD 0 August 7, 2014 13:42
how to set nut and nuTilda? aynjust OpenFOAM Pre-Processing 1 July 7, 2013 05:36
incorrect to use nuTilda wall functions for k-epsilon? newToOpenFoam OpenFOAM Pre-Processing 0 December 14, 2011 06:15
nut values asharma OpenFOAM 20 February 17, 2011 13:35


All times are GMT -4. The time now is 19:04.