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

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 August 16, 2011, 10:12 What is the Difference between Re=0 and Re=0.01 in Simulation of Viscoelastic Flow #1 New Member   Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 8 Sponsored Links 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, 10:26 #2 New Member   Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 8 BTW, when people simulate the case for Re=0, they just neglect the convective term in the momentum eqn.

 August 17, 2011, 03:11 #3 New Member   Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 8 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).

 August 18, 2011, 04:43 #4 New Member   Xingyuan Chen Join Date: Feb 2011 Location: Darmstadt Posts: 10 Rep Power: 8 still need help thanks

 August 9, 2012, 05:40 #5 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 8 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.

November 28, 2012, 13:14
#6
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Xingyuan Chen
Join Date: Feb 2011
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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?

November 28, 2012, 17:04
#7
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Filippo Maria Denaro
Join Date: Jul 2010
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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

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