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

shear rate and strain rate

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

Like Tree1Likes
  • 1 Post By Lilly

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 16, 2014, 02:51
Default shear rate and strain rate
  #1
Senior Member
 
Join Date: Feb 2011
Posts: 140
Rep Power: 15
Lilly is on a distinguished road
Dear all,

I still don't really understand why strain rate and shear rate seem to be equal in fluent!
I wrote a viscosity udf at which the viscosity is dependent on the shear rate (this is what the original publication says, but I also found some publications using this model who are calling it "strain rate").
I also read the following thread

http://www.cfd-online.com/Forums/flu...magnitude.html

in which a quotation of the Fluent manual can be found
Quote:
"Strain Rate (in the Derivatives... category) relates shear stress to the viscosity. Also called the shear rate ( in Equation 8.4-17), the strain rate is related to the second invariant of the rate-of-deformation tensor . Its unit quantity is time-inverse. In 3D Cartesian coordinates, the strain rate,, is defined as Eq. (30.4-30)"

which means: shear rate= strain rate

I also couldn't find any Macro concerning the shear rate, that's why I used C_STRAIN_RATE_MAG.
But I don't really understand whether this is right or wrong? Why is the shear rate equal to the strain rate in Fluent?

It would be really nice, if somebody could help me!
Thank you in advance!
Lilly
jotac likes this.
Lilly is offline   Reply With Quote

Old   August 29, 2014, 00:46
Default
  #2
Senior Member
 
Sangwoo Kim
Join Date: Jul 2014
Location: Seoul, South Korea
Posts: 115
Rep Power: 12
swtbkim is on a distinguished road
I'm sorry for posting here..
I'm also confused about it.
Clearly Fluent User Guide says that strain rate is equal to shear rate,
but why??

Anyone has an idea??

Thank you.
swtbkim is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Shear Strain Rate Dave442 Main CFD Forum 5 October 25, 2013 04:08
Shear Strain Rate in non-circular conduit raphaelroselli CFX 16 September 24, 2013 06:49
Blood and shear strain rate Dave442 CFX 2 July 27, 2012 06:10
What is wall shear stress and shear strain rate? warlocklw Main CFD Forum 2 May 21, 2012 06:16
About "Shear strain rate" leo1985 CFX 0 April 26, 2008 04:48


All times are GMT -4. The time now is 02:50.