[zwirekk]

Hi all,
I have problem with my UDF. I modeling convection in magnetic field and I need to define new source which have impact on my fluid. So I calculated gradient of magnetic field for every cell centred of my mesh. Now I have to make array with my calculated data, but i don't know how excactly do it. It is my UDF code but i know that something is wrong.
I will be grateful for your help.

[AlexanderZ]

this is your UDF

#include "udf.h"

#define N 2304
#define vf 0.000032768
#define xm -8.86E-9
#define ro 997.96
#define beta 21.37E-5
#define To 293
#define mi 9.84E-4

float GradB[N] =
{.......}    

Temp=C_T(c,t);

DEFINE_SOURCE(xmagnetic_source,c,t,dS,eqn)
{
	real xm_source;
		thread_loop_c(t,d)	// loop over all cells in model
	{
		begin_c_loop(c,t)
		{
				xm_source=-(xm*ro*beta*(Temp-To)*GradB*vf)/(2*mi)
				}
			}
		}
		end_c_loop (c,t)
	}
	
return xm_source;
	
}

DEFINE_SOURCE(ymagnetic_source,c,t,dS,eqn)
{
	real ym_source;
		thread_loop_c(t,d)	// loop over all cells in model
	{
		begin_c_loop(c,t)
		{
				ym_source=-(xm*ro*beta*(Temp-To)*GradB*vf)/(2*mi)
				}
			}
		}
		end_c_loop (c,t)
	}
	
return ym_source;
	
}

it has several problems.

but first of all, what information does your array GradB contains? Why are you trying to multiply array on scalar?

best regards

[zwirekk]

GradB are values in every cell center of my geometry and gradB is used to get value of xm_source and ym_source.

[AlexanderZ]

using

thread_loop_c(t,d)	// loop over all cells in model
	{
		begin_c_loop(c,t)
		{

you make a loop over all cell in domain. so you should pick a value from your array and apply it to each cell. However, how do you know, that the order in your array and in loop is the same? You should think about it.
How did you get GradB?

Lets assume that the ordr is the same than you will get:

#include "udf.h"

#define N 2304
#define vf 0.000032768
#define xm -8.86E-9
#define ro 997.96
#define beta 21.37E-5
#define To 293
#define mi 9.84E-4

float GradB[N] =
{.......}  

DEFINE_SOURCE(xmagnetic_source,c,t,dS,eqn)
{
	real xm_source;
	real Temp;
	int i;
	i = 0;
		thread_loop_c(t,d)	// loop over all cells in model
		{
			begin_c_loop(c,t)
			{
				Temp = C_T(c,t);
				xm_source=-(xm*ro*beta*(Temp-To)*GradB[i]*vf)/(2*mi);
				C_UDMI(c,t,0) = GradB[i];
				C_UDMI(c,t,1) = xm_source;
				i++;
			}
			end_c_loop(c,t)
		}	
	return xm_source;
}

DEFINE_SOURCE(ymagnetic_source,c,t,dS,eqn)
{
	real ym_source;
	real Temp;
	int i;
	i = 0;
		thread_loop_c(t,d)	// loop over all cells in model
		{
			begin_c_loop(c,t)
			{
				Temp = C_T(c,t);
				ym_source=-(xm*ro*beta*(Temp-To)*GradB*vf)/(2*mi);
				C_UDMI(c,t,2) = ym_source;
				i++;
			}
			end_c_loop(c,t)
		}	
	return ym_source;
}

Using UDMIs you may make contors of your variables and check them.
Remember to allocate memory for UDMIs yousing Fluent GUI: User-Defined -> memory -> number of user-defined memory location -> set 3

best regards

[zwirekk]

Thanks for your reply.

I get GradB from Matlab. I copy coordinates of cell center in fluent and then I calculate value of GradB to my XY.

[zwirekk]

I don't know why i get error in line 12, there is my array.

[AlexanderZ]

you should put here output each time you have error, or any other question.

but this time most likely you forgot to put ; after {}

best regards

[zwirekk]

Hi AlexanderZ i corrected my mistakes which you mentioned me. Can you check this UDF one more time because I am getting two warrnings
Warning: line 2323: t definition shadows previous definition
Warning: line 2347: t definition shadows previous definition.
And I want to ask if it is possible to make contour in fluent with my values?
Thank you for help.

[AlexanderZ]

remove

Thread *t;

at lines : 2323 and 2347

threads are already defined in the header of each function,
for example here

DEFINE_SOURCE(ymagnetic_source,c,t,dS,eqn)

best regards

[zwirekk]

Thanks it help but now I have problem to start calculation. I get error and Fluent is crashing.
MPI Application rank 0 exited before MPI_Finalize() with status 2
The f1 process could not be started.

[AlexanderZ]

Remember to allocate memory for UDMIs yousing Fluent GUI: User-Defined -> memory -> number of user-defined memory location -> set 3

best regards

[zwirekk]

Hi sorry for so many questionons about this but i have problem. I allocate memory for UDMIs to number of user-defined memory location and number of user-defined memory location for node, next i choose source terms in cell zone conditions and next i initializate. I think my source should be in contours after initialization but something is wrong because nothing has change. Can anyone help me with this problem?

[zwirekk]

I also tried to compiled my udf in no parrarel mode but when i initializate my calculation my UDM are zero. And when i start calculation I get error received fatal signal.

[AlexanderZ]

for this code you need to allocate 4 UDMs, check it

best rergards

[zwirekk]

Originally Posted by AlexanderZ

for this code you need to allocate 4 UDMs, check it

best rergards

Hi i allocated 4 UDMs and something is wrong

[AlexanderZ]

check how many elements are in your model and how long is your array

best regards

[zwirekk]

Originally Posted by AlexanderZ

check how many elements are in your model and how long is your array

best regards

Thanks for reply. I checked number of elements and i have 94208 elements in mesh and the same in array. I dont know but when my UDF is interpreted very well. But the problem is to start calculation
best regards

[AlexanderZ]

load here your case file with all settings and udf

best regards

[Vikaskori]

hello,

i need udf file of the Magnetic body force
where can i get it?

[ammar-1990]

I need a UDF to add the effect of MHD on nanofluid flow,