Learning Forum

[Muhammad Ali Uzair]

Hi

What does the option "inject wallfilm particles" mean? How is it different from the wall film boundary condition in the boundary conditions panel? thanks

[Rob]

The wall film bc will take particles that hit the wall & form a film. The injection adds the particles to the wall directly: ie they don't fly around first.

[dineshad]

Hi Rob

I can't see the option of 'Inject Wallfilm Particles' in my setup. Any prerequisites options, I need to check for this?

Thank you

[Rob]

Check, you may need either transient flow or transient particles on a steady flow model. 

[dineshad]

Hi Rob, Thanks for the reply. The flow is transient. Actually, I am modeling water droplets impinging on a wall to form a film. I am considering the DPM-VOF model for it and giving 'wall film' as a boundary condition on a wall. Can you please tell me if it's necessary to check the above option as I am not able to see it? 

Thanks

[Rob]

If you have a wall film moving to VOF why do you inject wall film droplets?  Note, there are two wall film models Lagrangian (DPM based) and Eulerian (facet based) that don't work together. The former is a DPM boundary option (in walls), the other is a wall option with it's own tab. 

[dineshad]

Hi Rob

I am simulating VOF-DPM Simulation. In the model transition tab, I have given 'Volume-Equivalent Sphere Diameter Range' as 0 to 0.5mm. So I considered that it will write the inj file for all particles ranging between these two given values but it is only writing values around 0.1 or 0.2 mm. It has not written particles with small diameters(like 1e-6 or 1e-7) which are visible in the results. Can you please help me on how to include small particles also?

Thanks in advance.

 

[Rob]

The transition will give droplets based on the shear etc, smaller droplets may form from secondary break up in the DPM model (you need to turn that on too). To get droplets in the 0.1 to 1.0 micron range you'd need enough mesh to resolve them, that would be incredibly cpu intensive and a huge cell count.