[Hosea_Chan]

Dear forum users,

I am currently writing a code that sums the volume for 4 cell zones at the before the initialization, which the values will be used in 4 subsequent DEFINE_SOURCE macros. Specifically, I need to apply an x-momentum force that is dependent on the average velocity at the upstream face of the cell zone and apply the force evenly to the fluid body within the cell zone. Here is the portion of the code I have written for the volume sum:

#include "udf.h"
#define cell_zones 4

real total_volume[cell_zones];
real Ux[cell_zones];
int id_a[cell_zones] = {28,33,37,40}; /* get zone id of channel-in later, need input */
int id_v[cell_zones] = {9,10,11,12}; /* get zone id of channel volume later, need input */



DEFINE_ON_DEMAND(initialize)
{
	#if !RP_HOST

		Domain* d;
		
		int i;
		d = Get_Domain(1);
	
		for (i=0; i<4 ; i++) {
			Message0("Begin loop %d\n",i);
			cell_t c;
			Thread* t2 = Lookup_Thread(d,id_v[i]);
			begin_c_loop(c, t2) 
				{
				total_volume[i] += C_VOLUME(c,t2);
				}
			end_c_loop(c, t2)
			Message0("End loop %d\n",i);
			#if RP_NODE
				total_volume[i] = PRF_GRSUM1(total_volume[i]);
				
			#endif
			node_to_host_real_1(total_volume[i]);
			Message0("total_volume of zone %d: %12.4e\n", i,total_volume[i]);
			
		}
		#if RP_NODE

		#endif /* RP_NODE */
		
	#endif /* !RP_HOST */

}

However, when I execute this code through execute on demand, the code can execute to the end (as I have gotten the total volume displayed for all the cell zones) but Fluent are kept busy. I checked CPU usage and all the node processes are still busy as well. What could have gone wrong here? Thank you for the help in advance!

Best regards,
Hosea Chan

[AlexanderZ]

#include "udf.h"
#define cell_zones 4

real total_volume[cell_zones];
real Ux[cell_zones];
int id_a[cell_zones] = {28,33,37,40}; /* get zone id of channel-in later, need input */
int id_v[cell_zones] = {9,10,11,12}; /* get zone id of channel volume later, need input */



DEFINE_ON_DEMAND(initialize)
{
#if !RP_HOST

Domain* d;

int i;
d = Get_Domain(1);

for (i=0; i<4 ; i++) {
Message0("Begin loop %d\n",i);
cell_t c;
Thread* t2 = Lookup_Thread(d,id_v[i]);
begin_c_loop(c, t2)
{
total_volume[i] += C_VOLUME(c,t2);
}
end_c_loop(c, t2)
Message0("End loop %d\n",i);
#if RP_NODE
total_volume[i] = PRF_GRSUM1(total_volume[i]);

#endif
Message0("total_volume of zone %d: %12.4e\n", i,total_volume[i]);

}
#endif /* !RP_HOST */

}

[Hosea_Chan]

Dear Alex,

Thank you so much! The code works! So it seems like it is the line of

node_to_host_real1(total_volume[i]);

is holding up the macro. As I have defined total_volume as a global variable, do I need to transfer it back to the host so that the variable can be used in the subsequent macros? Thanks!

Best regards,
Hosea

[AlexanderZ]

usually, you want to return values to host in cases:
1. you want to read/write from/to file
2. you want to transfer values to cortex (to use in scheme code for instance)

so most likely you don't need to transfer.
But if you are going to transfer, read how to make it for arrays

Ansys Fluent Customization manual

[Hosea_Chan]

Dear Alex,

Thank you very much for your clear explanation! This is a great help over the manual text!

Best regards,
Hosea