I try to implement a new numerical model called "Fictitious Particle Method” on the conventional CFD-DEM. This method uses for systems that have particles with a large difference in size (10 to 20 times).

In this method, the amount of momentum exchange between the fluid and the solids is estimated by assuming that large solid consists of small, dense fictitious particles. (as shown in the below figures)

For the implementation of this method, I need to change some equations that used in conventional CFD-DEM. Such as:

• Gas void fraction equation

• Sauter mean diameter that used in Reynolds number and β equation

• The average velocity of all solids existing in a computational cell.

• The equation of drag force acting on particles and coarse solid.

Finally, my question is how and with which subroutines can these changes be made?

Thank you very much for your help.