CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Suggestion on new dynamic viscosity expression in CFX

Register Blogs Community New Posts Updated Threads Search

Like Tree3Likes

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 13, 2018, 02:32
Default
  #21
Member
 
Dr Gurubasavaraju
Join Date: Dec 2014
Location: Bengaluru India
Posts: 77
Rep Power: 11
gbrajtm is on a distinguished road
Hi,

I am trying to implement HB model (Discussed in this thread) in transient analysis. Below is the CEL code I used. But I am getting an error (see attachment) any specific reason for this error.

CEL:
&replace EXPRESSIONS:
Bounded = min(max(Shear Strain Rate,MinValue[s^-1]),MaxValue[s^-1])
HB = ((1-exp(nu0*Bounded/tau0))*((tau0/Bounded)+K*Bounded^(n-1)))
K = 2 [Pa s^0.3]
MaxValue = 1.0e+10
MinValue = 1.0e-10
n = 0.3
nu0 = 0.6 [Pa s]
tau0 = 4000 [kg m^-1 s^-2]
END
END
END
Attached Images
File Type: jpg Error.JPG (56.4 KB, 10 views)
gbrajtm is offline   Reply With Quote

Old   June 13, 2018, 02:50
Default Suggestion on new dynamic viscosity expression in CFX
  #22
New Member
 
Titus Ofei
Join Date: Nov 2012
Posts: 14
Rep Power: 13
TitusOfei is on a distinguished road
Hi, floating error could be due to anything including poor meshing as well transient solution setup.
Again looking at your values, nu0 is too small and tau0 is too large. I think you have interchanged these values. Have a second look.
gbrajtm likes this.
TitusOfei is offline   Reply With Quote

Old   June 13, 2018, 04:07
Default
  #23
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 669
Rep Power: 22
Lance is on a distinguished road
Quote:
Originally Posted by gbrajtm View Post
K = 2 [Pa s^0.3]
Im not sure that CFX accept non-integer exponents.
gbrajtm likes this.
Lance is offline   Reply With Quote

Old   June 13, 2018, 04:31
Default
  #24
Senior Member
 
Gert-Jan
Join Date: Oct 2012
Location: Europe
Posts: 1,831
Rep Power: 27
Gert-Jan will become famous soon enough
I don't think it has anything to do with poor meshing ot transient solution setup, since your message already appears in the initialisation (see error messaage).
So, I think Titus is correct that something is wrong with your expression.
Did you evaluate the expressions in Pre, using the plotting function?
Alternatively, perform a first run with mild (small range) settings to get a reasonable initial guess and then your final case with the first run as initial guess.
gbrajtm likes this.
Gert-Jan is offline   Reply With Quote

Old   June 14, 2018, 00:36
Default
  #25
Member
 
Dr Gurubasavaraju
Join Date: Dec 2014
Location: Bengaluru India
Posts: 77
Rep Power: 11
gbrajtm is on a distinguished road
Quote:
Originally Posted by TitusOfei View Post
Hi, floating error could be due to anything including poor meshing as well transient solution setup.
Again looking at your values, nu0 is too small and tau0 is too large. I think you have interchanged these values. Have a second look.
Thank you, It was an issue with the values....
gbrajtm is offline   Reply With Quote

Old   June 14, 2018, 00:37
Default
  #26
Member
 
Dr Gurubasavaraju
Join Date: Dec 2014
Location: Bengaluru India
Posts: 77
Rep Power: 11
gbrajtm is on a distinguished road
Quote:
Originally Posted by Gert-Jan View Post
I don't think it has anything to do with poor meshing ot transient solution setup, since your message already appears in the initialisation (see error messaage).
So, I think Titus is correct that something is wrong with your expression.
Did you evaluate the expressions in Pre, using the plotting function?
Alternatively, perform a first run with mild (small range) settings to get a reasonable initial guess and then your final case with the first run as initial guess.
yes, values in the expressions were wrong....Thank you
gbrajtm is offline   Reply With Quote

Reply


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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
solid particle dynamic viscosity trinitron CFX 0 August 2, 2012 03:45
CGNS lib and Fortran compiler manaliac Main CFD Forum 2 November 29, 2010 06:25
dynamic viscosity setup fat bug CFX 5 March 20, 2008 11:01
Does CFX support LES, local dynamic mdoel JJ CFX 0 August 28, 2003 21:15
CFX 4.4 installation problem Pandu Sattvika CFX 1 December 1, 2001 04:07


All times are GMT -4. The time now is 20:17.