[sujay]

Dear Friends,

I want to inject particles into the water tank and want to check how many are going out of the water tank through the outlet and how many are floated to top surface (Transient case) . Theses particles are continuously entering through the inlet pipe (along with water). These particles are slightly lighter than water.

Materiel used are Water as Fluid and Particles as Dispersed Solid.

Problem associated are
1) Particle material properties : only density of particle is asked while creating material . Do i need to add any other property ?

2) Modelling of drag force: with default Cd = 0.44 all particles are floated to top surface.

Actually some particles are expected to leave tank through outlet along with water (~ 25 %) depending on the particle size.

How to simulate this in CFX.

Thank You,
Sujay

[ghorrocks]

Are you doing this with a lagrangian particle tracking model, or a eularian model?

What other particle properties do you want to add?

If all the particles are floating to the surface but in reality about 25% exit through the water outlet then one of two things has occurred:
* Your simulation is not numerically accurate. Check your simulation is converged, your model constants are correct and your mesh size is OK
* You have chosen the wrong physical models. Particles with Cd=0.44 float to the top, so what would make some of them remain in the water? Is there a turbulent dispersion force? Is the flow more turbulent than you have modelled? Is there forces acting on the particles other than drag and buoyancy (such as particle dispersion forces, agglomeration forces, sticking to walls)?

[sujay]

Lagrangian particle tracking model is used.

The particle properties like surface tension or contact angle between fluid and particle.

The tracking of the particle is continued till the maximum distance /time /time step and restitution coefficient defines sticking of particle to wall (here i am considering as particles floated to top). The flow is first solved for flow and then particles were injected and tracked with initial flow properties from the result file of flow. Mesh was checked.

I have considered only drag and buoyancy forces with turbulent flow. k-e turbulent model is used at inlet. Can you point what things to be added and if so will they have that much effect (25 % are expected to leave through outlet)

[ghorrocks]

Why is surface tension and contact angle important? If the particles are completely covered in liquid then these properties do not matter. Can you explain why this is important?

I have already listed in the previous post a few things to consider for what you might be missing. I will not comment further until you try those ideas.

[dotapro]

Can you explain the reason you made the assumption (25% are expected to leave through outlet)? Have a look at multiphase tutorial for better understanding.