[HHOS]

Hello,


I am trying to get an udf working for a modified particle drag. As a testing experiment, I am running some simulations trying to mimick the Morsi-Alexander Drag Law with an UDF. Running the test case, where I simply have a straight pipe with the default Fluent code and with my UDF, I am not getting the same values, and I don't really know why... The code I have used is below.


At this thread they claim that it works, but I don't really know how they managed...


The deviation I get from using the UDF or the Fluent embedded code is shown in the figure:






Any ideas??


Thanks and regards.

#include "udf.h"
DEFINE_DPM_DRAG(particle_drag_force, Re, p)
{
    real drag_force;
    real w;
    w=18*Re/24;
    if (Re < 0.01)
        {
            drag_force=18;
            return (drag_force);
        }
    else if (0.1 < Re < 1)
        {
            drag_force = (22.73/Re+0.0903/pow(Re,2)+3.69)*w;
            return (drag_force);
        }
    else if (1 < Re < 10)
        {
        drag_force = (29.1667/Re-3.8889/pow(Re,2)+1.222)*w;
        return (drag_force);
        }
    else if (10 < Re < 100)
        {
            drag_force = (46.5/Re-116.67/pow(Re,2)+0.6167)*w;
            return (drag_force);
        }
    else if (100 < Re < 1000)
        {
            drag_force = (98.33/Re-2778/pow(Re,2)+0.3644)*w;
            return (drag_force);
        }
    else if (1000 < Re < 5000)
        {
            drag_force = (148.62/Re-47500/pow(Re,2)+0.357)*w;
            return (drag_force);
        }
    else if (5000 < Re < 10000)
        {
            drag_force = (-490.546/Re-578700/pow(Re,2)+0.46)*w;
            return (drag_force);
        }
    else
        {
            drag_force = (-1662.5/Re+5.4167*pow(10,6)/pow(Re,2)+0.5191)*w;
            return (drag_force);
        }
}

[user_epsilon]

Did you find a solution? I have similar code and the results are about the same for some particle sizes but quite off for others

[HHOS]

Unfortunately did not, sorry.