[souria]

Hey every one,

I'm trying to adapt an UDF to follow particles, so in Fluent-UDF-Manuel I fund some examples, I want to know what does mean this :

alpha = M_PI/2. - acos(MAX(-1.,MIN(1.,NV_DOT(normal,P_VEL(p))/
MAX(NV_MAG(P_VEL(p)),DPM_SMALL))))

I understand : NV_DOT(normal,P_VEL(p))/(NV_MAG(P_VEL(p))

But I have no idea about the presence of MIN, MAX, DPM_SMALL

PS. Alpha is the angle of particle path with face normal

I hope I'm clear
Thanks for your help

[CeesH]

Hi Souria,

MIN and MAX are functions to select a value.
For example, MIN(1.,NV_DOT(normal,P_VEL(p)) will give as an output the minimum of 1 and NV_DOT(normal,P_VEL(p)). So, if NV_DOT(normal,P_VEL(p)) is larger than 1, the output is 1, otherwise it is whatever value the above expression has. MAX does the same, but selecting the maximum.

DPM_SMALL I guess is some macro that has a certain value; it's basically just a number. So the line MAX(NV_MAG(P_VEL(p)),DPM_SMALL)))) says: pick whatever is larger, NV_MAG(P_VEL(p)) or DPM_SMALL.

I hope that answers your question!

Best,
Cees

[souria]

Originally Posted by CeesH

Hi Souria,

MIN and MAX are functions to select a value.
For example, MIN(1.,NV_DOT(normal,P_VEL(p)) will give as an output the minimum of 1 and NV_DOT(normal,P_VEL(p)). So, if NV_DOT(normal,P_VEL(p)) is larger than 1, the output is 1, otherwise it is whatever value the above expression has. MAX does the same, but selecting the maximum.

DPM_SMALL I guess is some macro that has a certain value; it's basically just a number. So the line MAX(NV_MAG(P_VEL(p)),DPM_SMALL)))) says: pick whatever is larger, NV_MAG(P_VEL(p)) or DPM_SMALL.

I hope that answers your question!

Best,
Cees

Thanks CeesH for your quick answer.
it helps me a lot
Have a nice day