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-   -   What is the Difference between Re=0 and Re=0.01 in Simulation of Viscoelastic Flow (https://www.cfd-online.com/Forums/main/91596-what-difference-between-re-0-re-0-01-simulation-viscoelastic-flow.html)

 andreachan August 16, 2011 10:12

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

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?

 andreachan August 16, 2011 10:26

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

 andreachan August 17, 2011 03:11

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 04:43

still need help

thanks

 amin144 August 9, 2012 05:40

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 (Post 376159) 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 (Post 394705) 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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