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-   -   Herschel-Bulkley model (http://www.cfd-online.com/Forums/openfoam-solving/119722-herschel-bulkley-model.html)

sharonyue June 23, 2013 21:17

Herschel-Bulkley model
 
Hi,

The Herschel-Bulkley (HB) non-Newtonian viscosity model in OpenFOAM allows for a transition to Newtonian behavior when the shear rate is very low, thereby eliminating the undesirable discontinuity in the function at zero stress..........More details see here
http://www.cfd-online.com/Forums/ope...ign-error.html

my problem is in the last post, Thank you all!

Tushar@cfd June 24, 2013 00:38

Quote:

Originally Posted by sharonyue (Post 435500)
Hi,

The Herschel-Bulkley (HB) non-Newtonian viscosity model in OpenFOAM allows for a transition to Newtonian behavior when the shear rate is very low, thereby eliminating the undesirable discontinuity in the function at zero stress..........More details see here
http://www.cfd-online.com/Forums/ope...ign-error.html

my problem is in the last post, Thank you all!

Good work.
Do you think any problem with the Model?

Actually, the model seems to be correct in the new versions of OF. Earlier it had problem as mentioned in the post but later it was corrected.

sharonyue June 25, 2013 05:30

Quote:

Originally Posted by Tushar@cfd (Post 435509)
Good work.
Do you think any problem with the Model?

Actually, the model seems to be correct in the new versions of OF. Earlier it had problem as mentioned in the post but later it was corrected.

Hi Tushar,

I dont know thats thread's mean, is there any difference between tau0 and tauy?

Thanks

Tushar@cfd June 26, 2013 01:19

Quote:

Originally Posted by sharonyue (Post 435767)
Hi Tushar,

I dont know thats thread's mean, is there any difference between tau0 and tauy?

Thanks

Hello sharonyue,

May be, the author might have described in that manner.

As, far as I know:
when shear-rate = 0 then tauyx < tau0
Later with, shear-rate > 0, tauyx > tau0, and we have the model equation for the same.

Correct me, if I am wrong..

:)

Tushar@cfd June 26, 2013 03:49

http://www.cfd-online.com/Forums/ope...ign-error.html

tauy=tau0 in the present model when shear-rate = 0 (low shear rate)
I think author did found some relationship based on which he concluded tauy is not the same.

If you happen to see the fluent code,
It also contains same equation for the model just like the OpenFOAM code.

Anyways, this one seems to be a good post for debate.

sharonyue July 8, 2013 23:36

Quote:

Originally Posted by Tushar@cfd (Post 436015)
http://www.cfd-online.com/Forums/ope...ign-error.html

tauy=tau0 in the present model when shear-rate = 0 (low shear rate)
I think author did found some relationship based on which he concluded tauy is not the same.

If you happen to see the fluent code,
It also contains same equation for the model just like the OpenFOAM code.

Anyways, this one seems to be a good post for debate.

Sorry, very late.

But Im still confused about this tao0 and tauy, in HB model, there is only one taoy. Can you explain it more? With a image is the best. Thanks very much.


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