Hello again,

I am modelling a channel with the properties below;

There is a carrier flow in the +x direction with solid particles inside. And there is a cross flow (of the same fluid) without particles in the -z direction. So, with the effect of the cross flow, the particles in the carrier fluid are moved to the direction of -z (to the accumulation wall) and of course at the same time in the +x direction by the carrier flow. So, I have to analyse those solid particles in the carrier flow.

For this reason, I used Lagrangian Model and I got some good results. My design of channel is right and I get right results.

But for very small particles (less than 10 micron), I have to consider also another phenomena, but I have difficulties in adding this phenomena to the model. It is that;

This cross flow is called field. So, there is FIELD-DRIVEN TRANSPORT in the -z direction. And there is DIFFUSION-DRIVEN TRANSPORT in the +z direction. For bigger particles, diffusion driven transport is neglected and I have already modelled them but for small particles the influence of this diffusion driven transport make the result totally the opposite to other case, so can not be neglected. So, I need to add this to the model somehow. I tried some solutions that came to my mind but they did not give the needed results.

If you know with which feature of STAR-CD I can model it pls. tell me. The problem is that I have only one month to finish my thesis and if I can not find this solution I will need to prolong it one more semester and I really do not want it.

Thanx in advance, selen

For the diffusion of the smallest particles, you can may be neglect them in the lagrangian phase and model them as a scalar in the carrier and see how this scalar diffuses in the continuous carrier phase. This way you may as well specify your diffusivity using user coding.