bubble diameter distribution
 

Hello,
I am working on water-air flow thorugh horizontal channel. I use euler-euler mixture model for that. I want to give a bubble diameter distribution along radial direction instead of inserting a constant diameter value in the related menu. ( phases > secondary phase > diameter )
Below you can find the trial udf I wrote for that. y is the radial axis. I have the half of the channel thus y has the range between -r and +r, where r is the radius of the channel.

#include "udf.h"

DEFINE_PROPERTY(bubble_diameter,c,t)
{
real y;
real diameter= P_DIAM(c,t);

if (y < 0)
diameter = 0.001;

else
diameter = 0.005;

return diameter ;
}

I can interprate the udf successfully but after I initialize, it gives me the following error:

FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: ()

I think I have problems in the udf. I will be glad if someone could tell me what mistake I am doing.

Thanks in advance...