Calculating Gradient of a Scalar

ali hemmati · August 3, 2011, 05:17

Hello,

I am going to calculate gradient of a scalar (UDS) which is solved through iterations, and its quantity is known. Here is my 'on demand' UDF which tries(!) to store x-gradient of scalar 0 to scalar 1, yet after executing the UDF, I receive an 'ACCESS VIOLATION' error.
Would you please help me.

Thanks.

Code:

#include "udf.h"

DEFINE_ON_DEMAND(grad_calc)
{

Domain *domain;
Thread *t;
cell_t c;

domain = Get_Domain(1);

	thread_loop_c(t,domain)
	{
		begin_c_loop(c,t)
		{
			C_UDSI(c,t,1) = C_UDSI_G(c,t,0)[0];		
		}
		end_c_loop(c,t)
	}

}

Amir · August 3, 2011, 16:10

Did you activate 2 UDSs?
Did you set a command in TUI in order to store gradients during iteration?
if yes, before executing this macro, allocate 2nd UDS simply by patching it with arbitrary value.

Amir

ali hemmati · August 4, 2011, 05:05

Hi Amir,

Thanks for your help. I pursued these two methods and got desired solution:

1. I solved the problem with defining all UDSs before iterating.
2. I solved the problem just by defining scalar 0 and after convergence, I patched scalar 1 to fluid zone with arbitrary value.

Subsequent to things done above, I executed the UDF without any error.

Thanks again.

August 3, 2011, 05:17	Calculating Gradient of a Scalar	#1
ali hemmati New Member Ali Join Date: Mar 2011 Posts: 27 Rep Power: 15	Hello, I am going to calculate gradient of a scalar (UDS) which is solved through iterations, and its quantity is known. Here is my 'on demand' UDF which tries(!) to store x-gradient of scalar 0 to scalar 1, yet after executing the UDF, I receive an 'ACCESS VIOLATION' error. Would you please help me. Thanks. Code: #include "udf.h" DEFINE_ON_DEMAND(grad_calc) { Domain domain; Thread t; cell_t c; domain = Get_Domain(1); thread_loop_c(t,domain) { begin_c_loop(c,t) { C_UDSI(c,t,1) = C_UDSI_G(c,t,0)[0]; } end_c_loop(c,t) } }

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August 3, 2011, 16:10		#2
Amir Senior Member Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23	Did you activate 2 UDSs? Did you set a command in TUI in order to store gradients during iteration? if yes, before executing this macro, allocate 2nd UDS simply by patching it with arbitrary value. Amir

August 4, 2011, 05:05		#3
ali hemmati New Member Ali Join Date: Mar 2011 Posts: 27 Rep Power: 15	Hi Amir, Thanks for your help. I pursued these two methods and got desired solution: 1. I solved the problem with defining all UDSs before iterating. 2. I solved the problem just by defining scalar 0 and after convergence, I patched scalar 1 to fluid zone with arbitrary value. Subsequent to things done above, I executed the UDF without any error. Thanks again.