[ebtedaei]

Dear All,

Why are the simulation results of the vertical and angled geometries different?

Other simulation conditions are equal.

Thanks

[KaLium]

Do you have gravity in your simulation?

Maybe you should send some pictures and more information.

[ebtedaei]

Yes I have.

[ebtedaei]

Hi,
Some pictures are attached by this reply:

The result of the vertical case is correct but the angled incorrect! why?
The simulation conditions are equal and for both g=-9.81.

Please help me.
Thanks

[divergence]

If the gravity is affecting in the same direction (for instance -y direction) in both of the cases, the case is not the same. Additionally, the axial velocity parameter might fool you if the directions are changed. Try to plot the velocity profiles with velocity-magnitude and see if there is a big difference still. Anyhow, you could run a test case of the first case without gravity and see whether it is really necessary to have it included in the calculations.

[ebtedaei]

Originally Posted by divergence

If the gravity is affecting in the same direction (for instance -y direction) in both of the cases, the case is not the same. Additionally, the axial velocity parameter might fool you if the directions are changed. Try to plot the velocity profiles with velocity-magnitude and see if there is a big difference still. Anyhow, you could run a test case of the first case without gravity and see whether it is really necessary to have it included in the calculations.

Thank you for your suggestions. Before I answer you, I need to note that in my case gravity is really necessary to have it included in the calculations because it is a real case and gravity effects on it in the -y direction.

I performed them:
- I plotted the velocity profiles with the velocity-magnitude, also the pressure profiles with the pressure that their results were correct! So we conclude that for both Vertical and Diagonal geometries, the results of scalar parameters are similar and correct but the results of vector parameters are different and incorrect!!!

- I run a test case of vertical case without gravity and saw that the results was become incorrect! So it means that gravity is really necessary to have it included in the calculations.

Why the vector parameters are incorrect for Diagonal case?
Why the vector parameters are different for both vertical and Diagonal?

What changes should I do to correct the results of the diagonal case?

Thanks

[divergence]

I think that the axial, radial and tangential velocity parameters defined by Fluent rely completely on the axis definition. For instance, in the first picture you sent, the axial velocity parameter was illustrated, but in reality I would guess that it is the x-velocity (x-axis <--> axial direction in Fluent's mindset). You can check this theory by visualizing the x-velocity on the same plane as portrayed in figure 1 (vertical_velocity.jpg).

If you specifically want to use the axial, radial and tangential velocity parameters in post-processing, then you might have to rotate the axis in such order that the x-axis is the axial direction. Alternatively, you could try to create a custom field function from the x, y and z velocities in order to get axial velocity also for the 25 deg case. In any case, the velocity-magnitude parameter should give you correct answers in any case.

[ebtedaei]

Thanks for your help, I knew how to simulate the diagonal case. Actually, the geometry was held as fixed and vector g was distributed in X, Y and Z directions.

Now, I can't correctly simulate Tangential and Radial velocities (the results are in correct!!!) why?

Axial velocity = Y velocity
Tangential velocity = ?
Radial velocity = ?

Thank you for helping me.

[ebtedaei]

The correct figure of the diagonal case is attached by this post:

[KaLium]

I think that problem is in visualization, not in simulation.

Tangential and Radial velocity are hard to define unambiguously.