Get different value from FLUENT static pressure integration.

SNeCu · March 22, 2016, 09:29

I wrote following UDF to acquire pressure integration value of one flat boundary. However, the pressure integration function build in FLUENT gives me a totally different answer. Are there any problem in my code?

#include "udf.h"
#define rvol1_ID 22
DEFINE_EXECUTE_AT_END(pressureudf)
{
FILE *fp1;
real time1=CURRENT_TIME;
Domain *d;
Thread *thread;
face_t f;
double A[ND_ND];
double pressure=0.;
d= Get_Domain(1);
thread=Lookup_Thread(d, rvol1_ID);
begin_f_loop(f,thread)
{
F_AREA(A,f,thread);
pressure+=F_P(f,thread)*NV_MAG(A);
}
end_f_loop(f,thread)
fp1=fopen("pressure223.txt","a");
fprintf(fp1,"%g %g\n",time1,pressure);
fclose(fp1);

}

`e` · March 22, 2016, 16:58

The units of your variable 'pressure' is N (a force). Ensure your units are what you expect and whether or not gauge/dynamic/static pressure is used. For details on how Fluent treats pressure, have a read of this post.

SNeCu · March 23, 2016, 23:48

It is very weird that the problem is at fprintf(fp1,"%g %g\n",time1,pressure); which cannot show a correct answer. When I adjust the distance between time1 and pressure, it works and gives the same answer as FLUENT integral function.

March 22, 2016, 09:29	Get different value from FLUENT static pressure integration.	#1
SNeCu Member Nate Lau Join Date: Mar 2016 Posts: 33 Rep Power: 10	I wrote following UDF to acquire pressure integration value of one flat boundary. However, the pressure integration function build in FLUENT gives me a totally different answer. Are there any problem in my code? #include "udf.h" #define rvol1_ID 22 DEFINE_EXECUTE_AT_END(pressureudf) { FILE fp1; real time1=CURRENT_TIME; Domain d; Thread thread; face_t f; double A[ND_ND]; double pressure=0.; d= Get_Domain(1); thread=Lookup_Thread(d, rvol1_ID); begin_f_loop(f,thread) { F_AREA(A,f,thread); pressure+=F_P(f,thread)NV_MAG(A); } end_f_loop(f,thread) fp1=fopen("pressure223.txt","a"); fprintf(fp1,"%g %g\n",time1,pressure); fclose(fp1); }

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Wind tunnel Boundary Conditions in Fluent	metmet	FLUENT	6	October 30, 2019 13:23
static vs. total pressure	auf dem feld	FLUENT	17	February 26, 2016 14:04
Assign static pressure at inlet	Tanjina	FLUENT	0	November 3, 2013 12:34
Fluent natural ventilation pressure boundary condition	pierresandre	FLUENT	24	November 8, 2011 15:32
defining a term for a domain using DEFINE_ADJUST	MASOUD	Fluent UDF and Scheme Programming	1	September 24, 2010 06:08

March 22, 2016, 16:58		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	The units of your variable 'pressure' is N (a force). Ensure your units are what you expect and whether or not gauge/dynamic/static pressure is used. For details on how Fluent treats pressure, have a read of this post.

March 23, 2016, 23:48		#3
SNeCu Member Nate Lau Join Date: Mar 2016 Posts: 33 Rep Power: 10	It is very weird that the problem is at fprintf(fp1,"%g %g\n",time1,pressure); which cannot show a correct answer. When I adjust the distance between time1 and pressure, it works and gives the same answer as FLUENT integral function.