Power - Law Viscosity Model for Polymers

NickolasPl · August 12, 2011, 07:23

Hello everybody,

I'm working on a project for my Master Thesis and I m studying polymer rheology and polymer melt flow under certain geometries. I have benchmarked some very rough and primitive cases for polymer flows using power - law viscosity model and the results are very good. However, in polymer melts, the viscosity is strongly affected by the temperature and this is expressed as:

eta = eta0*exp[-b(T-Tref.)]

etao is the reference viscosity at the reference temperature Tref. b variable, is a value that shows how much the viscosity is affected by temperature and actually b values are tabulated and in many softwares this is an input value.
So my question is if this value is included in the power law viscosity model? I understand all tha input data in TransportProperties dictionary but I dont see anyware any input value for b. Can anyone help me out?is there a possibility to change the viscosity model so that the viscosity is affected by temperature through the b value?

Thanks in advance!

elvis · August 12, 2011, 08:19

Hi,

I just wanted to point out that there are many viscosity laws implemented by Jovani Favero.
These laws are only available on Of1.5-dev or Of1.6-extend not on OpenCFD version of Openfoam

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

NickolasPl · August 12, 2011, 08:26

thanx for your comment Elvis. I have seen this thread sometime ago but it covers a different subject of polymer rheology. However, I m gonna make a post there also. Thanx!

August 12, 2011, 07:23	Power - Law Viscosity Model for Polymers	#1
NickolasPl Member Nickolas P Join Date: Oct 2010 Location: Greece Posts: 30 Rep Power: 15	Hello everybody, I'm working on a project for my Master Thesis and I m studying polymer rheology and polymer melt flow under certain geometries. I have benchmarked some very rough and primitive cases for polymer flows using power - law viscosity model and the results are very good. However, in polymer melts, the viscosity is strongly affected by the temperature and this is expressed as: eta = eta0*exp[-b(T-Tref.)] etao is the reference viscosity at the reference temperature Tref. b variable, is a value that shows how much the viscosity is affected by temperature and actually b values are tabulated and in many softwares this is an input value. So my question is if this value is included in the power law viscosity model? I understand all tha input data in TransportProperties dictionary but I dont see anyware any input value for b. Can anyone help me out?is there a possibility to change the viscosity model so that the viscosity is affected by temperature through the b value? Thanks in advance!

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August 12, 2011, 08:19		#2
elvis Senior Member Elvis Join Date: Mar 2009 Location: Sindelfingen, Germany Posts: 620 Blog Entries: 6 Rep Power: 24	Hi, I just wanted to point out that there are many viscosity laws implemented by Jovani Favero. These laws are only available on Of1.5-dev or Of1.6-extend not on OpenCFD version of Openfoam http://www.cfd-online.com/Forums/ope...fluidfoam.html

August 12, 2011, 08:26		#3
NickolasPl Member Nickolas P Join Date: Oct 2010 Location: Greece Posts: 30 Rep Power: 15	thanx for your comment Elvis. I have seen this thread sometime ago but it covers a different subject of polymer rheology. However, I m gonna make a post there also. Thanx!