about custom drag in mixture model
 

I use a UDF program of customing drag in the mixture model. It is a program from the FLUENTUSERS.com and everything is ok and I compiled it successfully. the error occures immediately after I begin to iterate,It shows in the control window that : Updating solution at time level N... done. iter continuity x-velocity y-velocity z-velocity k epsilon uu-stress vv-stress ww-stress uv-stress vw-stress uw-stress vf-bub time/iter 99573 5.2328e-02 9.0766e-05 5.3900e-05 3.6095e-05 1.1646e-03 3.2961e-03 4.0613e-04 9.8431e-04 3.6854e-04 1.1754e-03 2.6536e-03 1.8777e-04 1.0813e-04 0:00:00 50

reversed flow in 4 faces on pressure-outlet 8.

reversed flow in 1382 faces on pressure-inlet 10.

Error: get_udf_function: function mzslip has wrong type: 3 != 4 Error Object: ()

what's is the mean of 'get_udf_function'? mzslip is a udf function in my UDF. If someone interested in it, I will send you the program.