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transportModel problem in interFoam

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Old   December 3, 2014, 00:07
Default transportModel problem in interFoam
  #1
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Yongxiao Wang
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Hi,
I want to simulate a non-Newtonian fluid flow by using interFoam solver.
I modified the transportProperties as follows:
Code:
water
{
    transportModel  poweLaw;
    nu              nu [ 0 2 -1 0 0 0 0 ] 0.001;
    rho             rho [ 1 -3 0 0 0 0 0 ] 1000;
    powerLawCoeffs
    {
        k               k [0 2 -1 0 0 0 0] 100;
        n               n [0 0 0 0 0 0 0] 0.1;
        nuMin         nuMin [0 2 -1 0 0 0 0] 1;
        nuMax        nuMax [0 2 -1 0 0 0 0] 10000;
    }
}
And I run it. It seems that everything is fine.
But the result of alpha.* is keeping the initial state. In other words, the fluid does not flow. And other results (U/P) are also not correct.
I modify the water transportModel to Newtonian, and run it again.
Everything is fine.

Maybe this problem is infantile, but as a beginner I still don't know where is wrong. Any help is greatly appreciated.
Thanks!

Yongxiao
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Old   December 3, 2014, 05:00
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  #2
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Tushar Chourushi
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Quote:
Originally Posted by Yanci View Post
Hi,
I want to simulate a non-Newtonian fluid flow by using interFoam solver.
I modified the transportProperties as follows:
Code:
water
{
    transportModel  poweLaw;
    nu              nu [ 0 2 -1 0 0 0 0 ] 0.001;
    rho             rho [ 1 -3 0 0 0 0 0 ] 1000;
    powerLawCoeffs
    {
        k               k [0 2 -1 0 0 0 0] 100;
        n               n [0 0 0 0 0 0 0] 0.1;
        nuMin         nuMin [0 2 -1 0 0 0 0] 1;
        nuMax        nuMax [0 2 -1 0 0 0 0] 10000;
    }
}
And I run it. It seems that everything is fine.
But the result of alpha.* is keeping the initial state. In other words, the fluid does not flow. And other results (U/P) are also not correct.
I modify the water transportModel to Newtonian, and run it again.
Everything is fine.

Maybe this problem is infantile, but as a beginner I still don't know where is wrong. Any help is greatly appreciated.
Thanks!

Yongxiao
Hi Yanci,

Do the following changes in your case file:

Code:
{
    transportModel  powerLaw;
    nu              nu [ 0 2 -1 0 0 0 0 ] 0.001;
    rho             rho [ 1 -3 0 0 0 0 0 ] 1000;
    powerLawCoeffs
    {
        k               k [0 2 -1 0 0 0 0] 100;
        n               n [0 0 0 0 0 0 0] 0.1;
        nuMin         nuMin [0 2 -1 0 0 0 0] 0.0001;
        nuMax        nuMax [0 2 -1 0 0 0 0] 10000;
    }
}
I hope it will work now.

-
Best Luck!
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Old   December 3, 2014, 07:45
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Yongxiao Wang
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Hi Tushar,
Thank you for your reply.
But it's still not working properly.
Everything is like before.
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Old   December 3, 2014, 08:48
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Tushar Chourushi
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Hello Yanci,

Are you comparing your results with some standards (papers)?

Also, check the values of the viscosity for both the Newtonian and Non-Newtonian fluids. What is the viscosity value for the Newtonian fluid when it runs fine?

-
Best Regards!
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Old   December 3, 2014, 09:57
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Yongxiao Wang
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Hi Tushar,
Yes,you are right.
I must say I didn't compare my results with any standard.
In the fact, this is just a test for my own transportModel. Because I encountered a similar problem, when I implement my viscosity model into the interFoam.
So I don't care too much about the specific value in this test.
But now I seem to know where is wrong after your reminder.
I set a large value for flow index (k) according to the previous. And it makes the viscosity values become too large. In a short period of time,its shape does not change obviously only under the influence of gravity. So the result of alpha.* is keeping the initial state. What do you think, am I right?
Thank you for your reply.

Best Regards!

Yongxiao
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Old   December 4, 2014, 00:22
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Tushar Chourushi
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Quote:
Originally Posted by Yanci View Post
Hi Tushar,
Yes,you are right.
I must say I didn't compare my results with any standard.
In the fact, this is just a test for my own transportModel. Because I encountered a similar problem, when I implement my viscosity model into the interFoam.
So I don't care too much about the specific value in this test.
But now I seem to know where is wrong after your reminder.
I set a large value for flow index (k) according to the previous. And it makes the viscosity values become too large. In a short period of time,its shape does not change obviously only under the influence of gravity. So the result of alpha.* is keeping the initial state. What do you think, am I right?
Thank you for your reply.

Best Regards!

Yongxiao
Hi Yanci,

Sorry for the late reply, I was offline.
You himself found the answer. You are correct with n=0.1, you are simulating the case of shear-thinning fluid. The large value of flow consistency index makes your fluid very thick in the very short period of time (or, for initial fluid viscosity is very high). This could be the reason for it's inability to capture the physics.

Anyways Best Luck for your future work.

-
Best Regards!
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