What is the Difference between Re=0 and Re=0.01 in Simulation of Viscoelastic Flow

andreachan · August 16, 2011, 11:12

Hello,

I have a question for quite a long time. When people simulate viscoelastic flow, they usually do the simulation at Reynolds Number Re=0, in order to simulate the creeping flow. However there is no physical meaning for Re=0, except that the velocity is 0. But when the velocity is 0 then actually there is no 'Flow'.

So why people simulate Re=0?

Why not do the simulation for Re=0.01 or smaller instead of Re=0? Is there great difference between the results of Re=0 and Re=0.01?

Thanks for your reply in advance!

andreachan · August 16, 2011, 11:26

BTW, when people simulate the case for Re=0, they just neglect the convective term in the momentum eqn.

andreachan · August 17, 2011, 04:11

one difference is, when we consider the elastic number E=Wi/Re, where Wi is the Weissenberg number, then Re=0 and Re=0.01 are great different. But the problem is the elastic number can be also calculated by E= viscosity*relaxation time/(density*length*length).

andreachan · August 18, 2011, 05:43

still need help

thanks

amin144 · August 9, 2012, 06:40

some models can't be used for Re=0 or Wi=0 because of being this numbers in denominator.
after this, Re=.000001 is creeping flow and in viscoelastic viscous forces ( they are dominant in creep flow even for newtonian) are very important.

andreachan · November 28, 2012, 13:14

Quote:

Originally Posted by amin144

some models can't be used for Re=0 or Wi=0 because of being this numbers in denominator.
after this, Re=.000001 is creeping flow and in viscoelastic viscous forces ( they are dominant in creep flow even for newtonian) are very important.

Could you please give me some examples that can not be used for Re=0?

FMDenaro · November 28, 2012, 17:04

Quote:

Originally Posted by andreachan

Could you please give me some examples that can not be used for Re=0?

Re=0 means simply that you are assuming:

Re * (du/dt + div (u u) + grad p') = Lap u = 0

this is more a mathematical assumption than a physical condition

August 16, 2011, 11:12	What is the Difference between Re=0 and Re=0.01 in Simulation of Viscoelastic Flow	#1
andreachan New Member Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 15	Hello, I have a question for quite a long time. When people simulate viscoelastic flow, they usually do the simulation at Reynolds Number Re=0, in order to simulate the creeping flow. However there is no physical meaning for Re=0, except that the velocity is 0. But when the velocity is 0 then actually there is no 'Flow'. So why people simulate Re=0? Why not do the simulation for Re=0.01 or smaller instead of Re=0? Is there great difference between the results of Re=0 and Re=0.01? Thanks for your reply in advance!

August 16, 2011, 11:26		#2
andreachan New Member Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 15	BTW, when people simulate the case for Re=0, they just neglect the convective term in the momentum eqn.

August 17, 2011, 04:11		#3
andreachan New Member Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 15	one difference is, when we consider the elastic number E=Wi/Re, where Wi is the Weissenberg number, then Re=0 and Re=0.01 are great different. But the problem is the elastic number can be also calculated by E= viscosityrelaxation time/(densitylength*length).

August 18, 2011, 05:43		#4
andreachan New Member Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 15	still need help thanks

August 9, 2012, 06:40		#5
amin144 Member Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 15	some models can't be used for Re=0 or Wi=0 because of being this numbers in denominator. after this, Re=.000001 is creeping flow and in viscoelastic viscous forces ( they are dominant in creep flow even for newtonian) are very important.