Menu

Discussion Forum

New Discussion
Filtra

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Carreau or Carreau-Yasuda model

Posted 26 mag 2015, 11:35 GMT-4 Fluid & Heat, Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.0 4 Replies

James Sparkes
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

Is there an easy way to use the more general CY model in COMSOL 5 rather than the carreau model?
4 Replies Last Post 10 giu 2015, 21:41 GMT-4
Steve Conrad
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 9 giu 2015, 11:22 GMT-4
I think Carreau and Carreau-Yasuda are used interchangeably and refer to the same. COMSOL uses for former term.

One has the option of selecting a user-defined model if the built-in models don't meet your needs.

--
Steven Conrad, MD PhD
LSU Health
I think Carreau and Carreau-Yasuda are used interchangeably and refer to the same. COMSOL uses for former term. One has the option of selecting a user-defined model if the built-in models don't meet your needs. -- Steven Conrad, MD PhD LSU Health
James Sparkes
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 10 giu 2015, 06:40 GMT-4
I have solved this problem using a user defined viscosity:

eta_0*(1+(lambda*spf.sr)^a)^((n-1)/a)

The Carreau model, with a=2, is a specific form of the more general carreau-yasuda model.
I have solved this problem using a user defined viscosity: eta_0*(1+(lambda*spf.sr)^a)^((n-1)/a) The Carreau model, with a=2, is a specific form of the more general carreau-yasuda model.
Himanshu Khandelwal
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 10 giu 2015, 10:04 GMT-4
Can you tell me how can I add herschel-bulkley parameters or Bingham Plastic properties?
Can you tell me how can I add herschel-bulkley parameters or Bingham Plastic properties?
Steve Conrad
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 10 giu 2015, 21:41 GMT-4
James, thanks for the clarification

Himanshu, you can provide any equation that provides a dynamic viscosity value, and you have the COMSOL variable spf.sr available for the shear rate.

I have not worked with Bingham fluids, but here are my thoughts. Consider using a very large limiting viscosity for a shear rate (spf.sr) under a given value (to simulate the yield stress), and the characteristic plastic viscosity above that value. The COMSOL if() function can be used to select the value based on shear rate. The result will have to be smoothed with a Heaviside function to eliminate the discontinuity.

This can be extended to the Herschel-Bulkley model by applying a shear thinning/thickening coefficient such as spf.sr^(n-1). The article at en.wikipedia.org/wiki/Herschel–Bulkley_fluid gives an even more generalized approach based on shear rate.

If anyone sees any problem with this approach, please advise!

--
Steven Conrad, MD PhD
LSU Health
James, thanks for the clarification Himanshu, you can provide any equation that provides a dynamic viscosity value, and you have the COMSOL variable spf.sr available for the shear rate. I have not worked with Bingham fluids, but here are my thoughts. Consider using a very large limiting viscosity for a shear rate (spf.sr) under a given value (to simulate the yield stress), and the characteristic plastic viscosity above that value. The COMSOL if() function can be used to select the value based on shear rate. The result will have to be smoothed with a Heaviside function to eliminate the discontinuity. This can be extended to the Herschel-Bulkley model by applying a shear thinning/thickening coefficient such as spf.sr^(n-1). The article at http://en.wikipedia.org/wiki/Herschel–Bulkley_fluid gives an even more generalized approach based on shear rate. If anyone sees any problem with this approach, please advise! -- Steven Conrad, MD PhD LSU Health

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content