helicoidal udf

Geeno

Hi all, I'm working on a 3d model of a heated cylinder and I should impose a helicoidal distribution of temperature as boundary condition on the external lateral surface,to simulate heat transfer with helicoidal external channels around the cylinder where a gas flows. Parametric equations of helix are: x=r*cos(t), y=r*sin(t), z=c*t, the curve lenght is: s=sqrt(r^2+c^2)*t, gas temperature in the channel is variable according with the following equations: T(s)=((Tmax-Tmin)/smax)*s+Tmin. Tmax,Tmin,c and smax are constant that I fix. Can anyone help me with this udf,I'm having a big trouble with its C programming. Thanks.