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Transient or Steady? What do you think?

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Old   April 9, 2015, 08:45
Default Transient or Steady? What do you think?
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Zhiyi Li
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Hallo everyone,

I am working on a cyclone simulation with only air inflow at the first place. Do you think I should use steady simulation or transient simulation? Since turbulence and the flow situation is changing after inflow of the air, should I use transient?

I used steady af first, even though my minimum othogonal mesh quality is 0.35, I could not get a converged (residual lower than 0.001) result after 5000 times of steady simulation. So I changed to transient after 5000 times of simulation, this time I got converged situation.

Do you think the method I used in the last paragraph is applicable? Or should I run the transient simulation at the first place? I am using 'Reynolds Stress Model (seven equation)'.

Thank you

Best Regards

Litchy
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Old   April 9, 2015, 08:50
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subhendu
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i think transient a you said it is changing with time
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Old   April 9, 2015, 15:35
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Hi,

We can get good converged solution with steady state itself.

What boundary conditions and discretization method are you using for the simulation?
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Old   April 10, 2015, 04:09
Default boundary condition and discretization method
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Zhiyi Li
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Quote:
Originally Posted by jsm View Post
Hi,

We can get good converged solution with steady state itself.

What boundary conditions and discretization method are you using for the simulation?
Thank you for your reply

The discretization method I used is velocity and pressure coupling: SIMPLE
Pressure: PRESTO! because of the highly swirl flow
And the other discretization methods keep default.

Boundary condition: Velocity_inlet: 10m/s and turbulent intensity:5%, hydraulic diameter: caulculated from the geometry, around 0.166m
pressure_outlet: others keep default, turbulent intensity:5%, hydraulic diameter:0.2m
The fluid is only air currently.

Solver is pressure based, raynolds stress method-7 equations method.

Do you think there may be some problems with my settings?

Best Regards

Litchy
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Old   April 10, 2015, 04:11
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Quote:
Originally Posted by subhsngh View Post
i think transient a you said it is changing with time
Well, it is changing first, when you put in the inflow air. But after a while, with the inflow air reach a balance, there is not much changing, I suppose
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