Thixotropy in Ansys CFX

thomas_blunschi · July 12, 2015, 08:07

How is it possible to implement thixotropic effects in CFX? I haven't figured out how this works so far and haven't found anything useful relating to this topic.

By the way, I am using the non-newtonian model Bird Carreau. So I can not simply implement a CEL (viscosity as a funtion of time) because with this model the viscosity is already a function of the shear rate.

I appreciate any help that you can provide.

thomas_blunschi · July 19, 2015, 06:22

Please, guys

ghorrocks · July 19, 2015, 08:11

You can define viscosity to be a function of time. Well, at least I think you can (I have not tried it). Give it a go and see what happens.

thomas_blunschi · July 19, 2015, 09:46

Thanks Glenn for your answer!
I would not ask if viscosity was only a function of time but it is already a function of shear rate. I've been searching for how to implement this function depending on two variables but without any success so far.
Do you know how to do this? Does it work with a 3d-Interpolation Data?

Best regards,
Thomas

ghorrocks · July 19, 2015, 19:39

Have you tried it? CFX will give you a warning/error message if you are trying to make viscosity a function of something it does not accept.

Also: This approach will only work when the second order terms (caused from the addition of time and shear rate terms in the viscosity term) are small enough to be insignificant. If these terms are big enough to be important then you will not be able to model it as only the primary effect (ie viscosity) will be included.

What function are you trying to implement? How are you trying to implement it?

July 12, 2015, 08:07	Thixotropy in Ansys CFX	#1
thomas_blunschi New Member Schweiz Join Date: Jan 2015 Posts: 6 Rep Power: 11	How is it possible to implement thixotropic effects in CFX? I haven't figured out how this works so far and haven't found anything useful relating to this topic. By the way, I am using the non-newtonian model Bird Carreau. So I can not simply implement a CEL (viscosity as a funtion of time) because with this model the viscosity is already a function of the shear rate. I appreciate any help that you can provide.

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July 19, 2015, 06:22		#2
thomas_blunschi New Member Schweiz Join Date: Jan 2015 Posts: 6 Rep Power: 11	Please, guys

July 19, 2015, 08:11		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	You can define viscosity to be a function of time. Well, at least I think you can (I have not tried it). Give it a go and see what happens.

July 19, 2015, 09:46		#4
thomas_blunschi New Member Schweiz Join Date: Jan 2015 Posts: 6 Rep Power: 11	Thanks Glenn for your answer! I would not ask if viscosity was only a function of time but it is already a function of shear rate. I've been searching for how to implement this function depending on two variables but without any success so far. Do you know how to do this? Does it work with a 3d-Interpolation Data? Best regards, Thomas

July 19, 2015, 19:39		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Have you tried it? CFX will give you a warning/error message if you are trying to make viscosity a function of something it does not accept. Also: This approach will only work when the second order terms (caused from the addition of time and shear rate terms in the viscosity term) are small enough to be insignificant. If these terms are big enough to be important then you will not be able to model it as only the primary effect (ie viscosity) will be included. What function are you trying to implement? How are you trying to implement it?