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Old   April 18, 2010, 06:03
Default Friction coefficient
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Belgio
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Help needed...

I am new to Flow3D, I'm trying to model the shock tube using the standard example model as a base. But it is impossible to change friction coefficient in turbulence settings (it is always -1.0). I've tried to change fluid viscousity and other parameters but that doesn't solve the problem. Friction is still -1.0.

Thanks in advance!
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Old   April 21, 2010, 19:10
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michael barkhudarov
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You need to activate the viscous model in Physics > Viscosity and Turbulence. Make sure also that there is a non-zero viscosity coefficient in the fluid properties.

Using a positive friction coefficient means a partial slip at walls. Is it what you want to do for the gas?
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Old   April 25, 2010, 13:34
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Yes, I've tried what you said. Nothing helps. Miha! Pls. check your private inbox. Thx
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Old   April 25, 2010, 18:39
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michael barkhudarov
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Gleb,

If you have viscous flow activated and the viscosity is positive, then there is friction at walls. The friction coefficient stays at -1, as it should for all fluid. The -1 value effectively means infinite no-slip BC. A 0 value would mean free slip, and a positive value means partial slip, which is suitable for solid-like materials.

The fact that you do not see a noticeable effect on the shock is probably because the viscous boudnary layer is too thin to be resolved.
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Old   March 8, 2011, 22:55
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Quote:
Originally Posted by Belgio View Post
Help needed...

I am new to Flow3D, I'm trying to model the shock tube using the standard example model as a base. But it is impossible to change friction coefficient in turbulence settings (it is always -1.0). I've tried to change fluid viscousity and other parameters but that doesn't solve the problem. Friction is still -1.0.

Thanks in advance!
dear Belgio,i have the same problem ,have you ever solved the problem?i want to set the frictional coefficient zero.thanks.
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Old   March 9, 2011, 04:30
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No, I have not solved that.
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Old   March 12, 2011, 18:28
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michael barkhudarov
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Quote:
Originally Posted by Belgio View Post
No, I have not solved that.
Hi guys,

Do I understand correctly that you have not been able to simulate a shock wave in a test tube because you could not set a friction coefficeint?
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