Learning Forum

[Saeed]

Hello,

Im doinf a cfd-dem simulation of a mixing tank. I think the results I am getting are not realistic. as you can see in the picture below, some of the particles pile up at bottom center or top center of the tank. my particles have density lest than the fluid so the should all go up. I have tried different time steps for both fluent and Rocky also different particle size and same thing happens. 

my cfd model is standard K-epsilone with scalable wall function and production limiter on. 

Thanks 

[Rob]

Is the mixer running? 

[Saeed]

Dear Rob, 

Thank you for your reply.

Yes it is running, even if it was not running the particles at the bottom should have a upward movment. 

Thanks 

[Rob]

Should they? What is the downwards fluid velocity relative to the Stokes terminal velocity?

[Saeed]

thank you for your reply.

The particle density is less thank fluid so it should be going up not to stay there and pile up.

The fluid z velocity in that region is about -0.2 m/s and stokes terminal velocity is -0.122 so their fraction is 1.63 . 

 

[Rob]

Downflow is 0.2m/s? 

[Saeed]

yes its almost 0.2 m/s 

[Rob]

And the terminal (floating) velocity is 0.122m/s?