Learning Forum

[Vicky]

Hello,
I am modeling a fluid of air and solid particles in a horizontal pipe, an unsteady fluid, DEM collision.

When I plot the DPM Velocity Magnitude, my results are consistent in the middle of the pipe but not near the wall. I've refined my mesh, and it stays about the same, meaning I don't get consistent results near the wall.
Could you explain why this is happening to me, or does it mean that the particles do not reach the wall?

Thank you.

 

[Nikhil N]

Hi, what do you mean by consistent? Are you comparing this with other similar simulations? If so, are you changing any settings?


'does it mean that the particles do not reach the wall?'

This depends on which forces are dominant. If the weight of the particles dominates over the pressure-gradient force of the continuous fluids, it should reach the wall (provided you have defined gravity correctly)

[Rob]

To add, if the near wall mesh is very fine the particles get trapped in the viscous sublayer. Wall contact is only checked in the near wall cell, so we can finish up with "large" particles travelling parallel to the wall in the next-but-one-cell-layer that should have hit it. That's where Ansys Rocky may come into it's own. 

[Vicky]

Hello,

I made a mistake in my description; I was referring to a vertical pipe.

My results are the following:

(I don't understand why I didn't get consistent results close to the wall)

 

thank you.

 

 

[Rob]

Can you plot DPM velocity contour and concentration; node values on & off?  I wonder if there aren't any particles to get the data off. 

[Vicky]

Hello Rob,

Thanks for your answer. Those are the results:

DPM - Velocity contour (left - contours on)

 

DPM Concentration (left - contours on):

 

Do you know why I have those results close to the wall?

[Rob]

In 2d don't select anything, that way you get the filled contour.  

I think your problem is not the result but a lack of particles in cells towards the wall. As there's no particle there's no data to return so the curves look odd.