[kdang]

Hello,

Could I get help with writing my first UDF in Fluent? I have written a UDF to assign a temperature to the cells whose z-coordinates are within a specified range. But it doesn't seem to work. Could everyone take a look at my code and point what I have done wrong?

I'm doing a series of transient simulations of the heat transfer between food cans and hot gas in a convection oven. I have a 228-in length filled with cans, and the can locations are periodic such that there are 19 units of cans. Each unit is 12 in long.

I want to use the UDF to set an initial temperature for the first unit of cans (Unit 1) and then solve for 16 s. Then, the current temperature of the Unit 1 will be the initial temperature of Unit 2. I will repeat this procedure until Unit 19.

I used DEFINE_ON_DEMAND instead of DEFINE_INIT because I'm using a steady-state solution as the initial solution for the hot gas.

Thank you so much in advance for your time and help!

#include "udf.h"

DEFINE_ON_DEMAND(can_unit_1_temp)
{
	/* declare domain pointer since it is not passed as an argument to the DEFINE macro */
	Domain *domain; 
	domain = Get_Domain(1); 

	/* get the cell thread pointer by using the macro Lookup_Thread(domain, zone_id) instead of thread *ct */
	int id = 55; /* ID of can solid cell zone */
	Thread *ct = Lookup_Thread(domain, id);

	cell_t c; /* cell index - an special Ansys Fluent data type */
	real pos[ND_ND];
 
	/* loop through all the cells in the cell thread of the can solid */
	begin_c_loop(c,ct)
	{
		C_CENTROID(pos,c,ct);
		if (0.1524 < pos[2] && pos[2] < 0.4572) /* the first 12 inch of cans (unit 1) is between 0.1524 and 0.4572 m */
			C_T(c,ct) = 600.0;
	}
	end_c_loop(c,ct)
}

[AlexanderZ]

code seems to be ok
by default fluent uses SI for all UNITs so check your values, that could be a problem

if (0.1524 < pos[2] && pos[2] < 0.4572)