non newtonian viscosity

mina.p · October 9, 2014, 17:06

Hi
To calculate the average velocity of ostwald de waele fluid flow at Re=50 as an inlet boundary, i need to write an expression for its viscosity first. can anybody help me to write this according m,n,max & min shear strain rate? is it possible?
thanks

ghorrocks · October 9, 2014, 18:58

If you know the viscosity function and parameters then why can't you calculate the viscosity?

mina.p · October 10, 2014, 02:34

Because of shear strain rate. In ostwald fluid we define max & min for shear strain rate so we have a span for it not a constant value.

ghorrocks · October 10, 2014, 02:40

You can access the shear strain rate variable in CFX, then you could use this in your calculation. This would make the boundary condition a function of the flow domain but often this sort of coupling works OK.

Alternately you could just estimate the SSR, maybe from a simple pipe flow or something with a simpler answer.

October 9, 2014, 17:06	non newtonian viscosity	#1
mina.p New Member mina Join Date: Nov 2013 Posts: 20 Rep Power: 13	Hi To calculate the average velocity of ostwald de waele fluid flow at Re=50 as an inlet boundary, i need to write an expression for its viscosity first. can anybody help me to write this according m,n,max & min shear strain rate? is it possible? thanks

October 10, 2014, 02:40		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	You can access the shear strain rate variable in CFX, then you could use this in your calculation. This would make the boundary condition a function of the flow domain but often this sort of coupling works OK. Alternately you could just estimate the SSR, maybe from a simple pipe flow or something with a simpler answer. mina.p likes this.

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October 9, 2014, 18:58		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	If you know the viscosity function and parameters then why can't you calculate the viscosity?

October 10, 2014, 02:34		#3
mina.p New Member mina Join Date: Nov 2013 Posts: 20 Rep Power: 13	Because of shear strain rate. In ostwald fluid we define max & min for shear strain rate so we have a span for it not a constant value.