CFD Online Discussion Forums - Fluent UDF and Scheme Programming http://www.cfd-online.com/Forums/ en Wed, 08 Sep 2010 12:35:33 GMT vBulletin 60 http://www.cfd-online.com/Forums/images/misc/rss.jpg CFD Online Discussion Forums - Fluent UDF and Scheme Programming http://www.cfd-online.com/Forums/ Nv-s ?? Nv-d ?? Help!!! http://www.cfd-online.com/Forums/fluent-udf/79904-nv-s-nv-d-help.html Wed, 08 Sep 2010 10:33:26 GMT
Quote:
#include "udf.h"
DEFINE_GRID_MOTION(plate,domain,dt,time,dtime)
{
Thread *tf = DT_THREAD(dt);
face_t f;
Node *v;
real NV_VEC(omega), NV_VEC(axis), NV_VEC(dx);
real NV_VEC(origin), NV_VEC(rvec);
real sign;
int n;
/* set deforming flag on adjacent cell zone */
SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));
sign = -5.0 * sin (26.178 * time);
Message ("time = %f, omega = %f\n", time, sign);
NV_S(omega, =, 0.0);
NV_D(axis, =, 0.0, 1.0, 0.0);
NV_D(origin, =, 0.0, 0.0, 0.152);
begin_f_loop(f,tf)
{
f_node_loop(f,tf,n)
{
v = F_NODE(f,tf,n);
/* update node if x position is greater than 0.02
and that the current node has not been previously
visited when looping through previous faces */
if (NODE_X(v) > 0.020 && NODE_POS_NEED_UPDATE (v))
{
/* indicate that node position has been update
so that it’s not updated more than once */
NODE_POS_UPDATED(v);
omega[1] = sign * pow (NODE_X(v)/0.230, 0.5);
NV_VV(rvec, =, NODE_COORD(v), -, origin);
NV_CROSS(dx, omega, rvec);
NV_S(dx, *=, dtime);
NV_V(NODE_COORD(v), +=, dx);
}
}
}
end_f_loop(f,tf);
}
I don't know that means. I didn't find a whole day in google and UDF manual.

please explain to me.. ]]> Fluent UDF and Scheme Programming oilsok http://www.cfd-online.com/Forums/fluent-udf/79904-nv-s-nv-d-help.html Heat generation is depend on x value and time. http://www.cfd-online.com/Forums/fluent-udf/79820-heat-generation-depend-x-value-time.html Sun, 05 Sep 2010 17:17:55 GMT Hi,

Heat generation is depend on x value and time in my simulation.
How to add x variation below code?

#include "udf.h"
DEFINE_SOURCE(heat_gen_time,cell,thread,dS,eqn)
{
real source;
real time;
time = CURRENT_TIME;
source = 86.44*pow(time,-.3);
dS[eqn] = -25.932*pow(time,-1.3);
return source;
} ]]> Fluent UDF and Scheme Programming omurakbayir http://www.cfd-online.com/Forums/fluent-udf/79820-heat-generation-depend-x-value-time.html ACCESS_VIOLATION error for tempreture jump boundary condition http://www.cfd-online.com/Forums/fluent-udf/79799-access_violation-error-tempreture-jump-boundary-condition.html Sat, 04 Sep 2010 12:22:10 GMT hi all I am trying to simulate heat transfer between parallel plates with tempreture jump boundary condition. this is my udf: #include... hi all

I am trying to simulate heat transfer between parallel plates with tempreture jump boundary condition.

this is my udf:

#include "udf.h"
#define TMAC 1
#define meanfreepath 6.8e-8
#define underrlx 0.02
#define SPHR 1.4
#define THAC 1
#define prandtl 0.707
DEFINE_PROFILE(temprature_jump_top,f_thread,index)
{
face_t f;

cell_t c;
Thread *cell_thread;
real gamma;
real temp;
begin_f_loop(f,f_thread)
{
c=F_C0(f,f_thread);

cell_thread=THREAD_T0(f_thread);
gamma=(2*SPHR)/(SPHR+1);
temp=(-2+THAC)/(THAC)*gamma*meanfreepath/prandtl*(C_T_G(c,cell_thread)[1]);
temp=(1-underrlx)*F_T(f,f_thread)+(underrlx*temp);
F_PROFILE(f,f_thread,index)=temp;
}
end_f_loop(face,f_thread)
}


but when i want to use them as a boundary condition,or when i want to iterate it,this error will be appear:

Error:
FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: ()

how can i solve this error?:(

I appreciate for any help ]]> Fluent UDF and Scheme Programming eeman http://www.cfd-online.com/Forums/fluent-udf/79799-access_violation-error-tempreture-jump-boundary-condition.html Use flow fild, but calculate only UDS http://www.cfd-online.com/Forums/fluent-udf/79604-use-flow-fild-but-calculate-only-uds.html Sat, 28 Aug 2010 10:11:19 GMT Is it possible to solve equations for UDS by UDF without flow calculation but with flow field from previous FLUENT solution (with scaled mesh)? Is it possible to solve equations for UDS by UDF without flow calculation
but with flow field from previous FLUENT solution (with scaled mesh)? ]]> Fluent UDF and Scheme Programming teop http://www.cfd-online.com/Forums/fluent-udf/79604-use-flow-fild-but-calculate-only-uds.html error while running the udf http://www.cfd-online.com/Forums/fluent-udf/79551-error-while-running-udf.html Thu, 26 Aug 2010 19:29:23 GMT hello everyone.... now the udf is compiling and loading without error... but while running the simulation at the bigining itself giving error, says... hello everyone....
now the udf is compiling and loading without error...
but while running the simulation at the bigining itself giving error, says
Absolute pressure Limited to 1.0000e+00 in zone 2
Error:> (Greater-than) : invalid argument [2] : wrong type [not a number]
Error object : nan
what it means.. where should i correct..

thanks
sugu ]]> Fluent UDF and Scheme Programming sugumaran http://www.cfd-online.com/Forums/fluent-udf/79551-error-while-running-udf.html Problems with hooking UDF http://www.cfd-online.com/Forums/fluent-udf/79526-problems-hooking-udf.html Thu, 26 Aug 2010 09:31:42 GMT Hello, I cant seem to hook my UDF onto my model, I can interept my code into Fluent with no problems but when trying to hook my UDF then my source... Hello,
I cant seem to hook my UDF onto my model, I can interept my code into Fluent with no problems but when trying to hook my UDF then my source terms do not appear as extra options and when I do hook any of the functions then I get a ACCESS_VIOLATION error.
Does anyone know why my source terms would not be available for hooking?
Thanks for any help ]]> Fluent UDF and Scheme Programming whelk123 http://www.cfd-online.com/Forums/fluent-udf/79526-problems-hooking-udf.html UDF for Boundary layer at inlet for cavity study http://www.cfd-online.com/Forums/fluent-udf/79525-udf-boundary-layer-inlet-cavity-study.html Thu, 26 Aug 2010 09:22:46 GMT hii.. m' working on cavity flow study.. i need a boundary layer of 5mm in front of the cavity. i need the equation of boundary layer velocity profile for the UDF n also i want to know the macro to be used for compressible fluid where pressure inlet boundary is given at inlet instead of velocity inlet... plzz sme1 guide me
thank u ]]> Fluent UDF and Scheme Programming vasuaero1988 http://www.cfd-online.com/Forums/fluent-udf/79525-udf-boundary-layer-inlet-cavity-study.html Ramp BC per Iteration http://www.cfd-online.com/Forums/fluent-udf/79494-ramp-bc-per-iteration.html Wed, 25 Aug 2010 15:21:30 GMT I have a converged Steady State solution. I am running a family of solutions with slightly different boundary conditions. In this case I am varying... I have a converged Steady State solution. I am running a family of solutions with slightly different boundary conditions. In this case I am varying the swirl at an inlet. For low values of swirl I find that I can use the existing solution simply change the values and keep running. As the absolute value gets large, I find that the amount of change the solution can absorb without diverging gets small. Even with signifcant relaxation and a small CFL number.

I think it would be simplest to define a UDF which ramps the swirl from one value to the next over some number of iterations. I understand how to define the profile, but not how to access the iteration number in an UDF.

Any help is appreciated
Thanks
- Andy R ]]> Fluent UDF and Scheme Programming AndyR http://www.cfd-online.com/Forums/fluent-udf/79494-ramp-bc-per-iteration.html ACCESS_VIOLATION error http://www.cfd-online.com/Forums/fluent-udf/79479-access_violation-error.html Wed, 25 Aug 2010 09:10:16 GMT Hello, I am trying to model the heat transfer within a hydrogen fuel cell and I keep getting the message ACCESS_VIOLATION when I try applying my UDF.... Hello, I am trying to model the heat transfer within a hydrogen fuel cell and I keep getting the message ACCESS_VIOLATION when I try applying my UDF.
#include "udf.h"
DEFINE_INIT(init_func,d)
{
Domain *d;
Thread *t;
real sum_diss=0.;
cell_t c;
d = Get_Domain(1);
}
DEFINE_SOURCE(sink_mass, c, t, dS, eqn)
{
real sink_mass;
sink_mass=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros);
return sink_mass;

}
DEFINE_SOURCE(energy_source, c, t, dS, eqn)
{
real energy_source;
energy_source=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros)*deltah/mh2;
return energy_source;
}
DEFINE_EXECUTE_AT_END(execute_at_end)
{
real step =RP_Get_Real("physical-time-step");
Domain *domain = Get_Domain(1);
int ID=2;
Thread *t =Lookup_Thread(domain, ID);
cell_t c;
begin_c_loop(c,t)
{
double temper,P,hsmp,lnpeq,Peq, dxdt;
temper=C_T(c,t);
P=(C_R(c,t)*rgp*C_T(c,t)/mh2)*0.00001;


hsmp= C_UDMI(c,t, 1 )*(HsMmaxprim-hsurm)+hsurm;
lnpeq=A-B/temper+C*hsmp+D*pow(tan(pi*hsmp/2.0/HsMmaxprim),n)+E*pow(tan(pi*hsmp/2.0/HsMmaxprim),(-m));
Peq=exp(lnpeq);
C_UDMI(c,t,0)=mh2*Ca*exp(Ea/(rgp*temper))*log(P/Peq)/0.0166;
C_UDMI(c,t,1 )=C_UDMI(c,t,1 )+C_UDMI(c,t,0)*step;
}
end_c_loop(c,t)
}

I have defined things but didnt think that was important. Can anyone please tell me what is wrong with this code!! It is fairly urgent!
Thank you for any help ]]> Fluent UDF and Scheme Programming whelk123 http://www.cfd-online.com/Forums/fluent-udf/79479-access_violation-error.html error in compiling udf http://www.cfd-online.com/Forums/fluent-udf/79463-error-compiling-udf.html Tue, 24 Aug 2010 18:54:37 GMT hello everyone...
i wrote my udf for real gas model... while compiling i got error message like this,,
1 file(s) copied.
(system "copy C:\Fluent.Inc\fluent6.3.26\src\makefile_nt.udf libudf\ntx86\2d\makefile")
1 file(s) copied.
(chdir "libudf")()
(chdir "ntx86\2d")()
'nmake' is not recognized as an internal or external command,
operable program or batch file.
'nmake' is not recognized as an internal or external command,
operable program or batch file.

Done.
"e:/sugu/vt/2d cases/gambit files/mesh files"

Opening library "libudf"...
Error: open_udf_library: The system cannot find the file specified.

Error Object: ()
this udf file is just example given in fluent manual only... still i m getting probs....
please help me... ]]> Fluent UDF and Scheme Programming sugumaran http://www.cfd-online.com/Forums/fluent-udf/79463-error-compiling-udf.html Boundary conditions by UDF http://www.cfd-online.com/Forums/fluent-udf/79418-boundary-conditions-udf.html Mon, 23 Aug 2010 15:30:55 GMT Dear all, I am new in CFD world. I want to write UDF for boundary conditions. My boundary conditions are as following: at interface :... Dear all,

I am new in CFD world. I want to write UDF for boundary conditions. My boundary conditions are as following:

at interface : Temperature fluid 1 = Temperature fluid 2
also for mass transfer : Relative humidity fluid 1= Relative Humidity fluid 2

I do not know, how can explain this relation by C program in UDF.

I appreciate if you kindly help me. please write or send me some examples.

Samaneh ]]> Fluent UDF and Scheme Programming s.sami http://www.cfd-online.com/Forums/fluent-udf/79418-boundary-conditions-udf.html Errors when interpreting UDF http://www.cfd-online.com/Forums/fluent-udf/79408-errors-when-interpreting-udf.html Mon, 23 Aug 2010 12:27:42 GMT I wrote a udf for thermal conductivity dependent on a temperature.
#include "udf.h"
DEFINE_PROPERTY(cell_thermalconductivity,cell,thre ad)
{
real ktc;
real temp = C_T(cell,thread);
ktc=(0.6*(1+(0.023*((pow(temp,1.2321))/(pow(10,(363.94/(temp-140))))))));
}
when I run fluent,I see this error:
Error: Floating point error: invalid number
Error Object: ()
could you help me?
thanks ]]> Fluent UDF and Scheme Programming elah599 http://www.cfd-online.com/Forums/fluent-udf/79408-errors-when-interpreting-udf.html 1/7 prandtle velocity profile http://www.cfd-online.com/Forums/fluent-udf/79358-1-7-prandtle-velocity-profile.html Sat, 21 Aug 2010 10:44:14 GMT i need profile 1/7 prandtle for inlet rectangular surface for pressure inlet boundary condition. is it possible set top udf(1/7 prandtle velocity... i need profile 1/7 prandtle for inlet rectangular surface for pressure inlet boundary condition.
is it possible set top udf(1/7 prandtle velocity profile) on pressure inletboundarycondition?
Thanks in advance. ]]> Fluent UDF and Scheme Programming behnam87 http://www.cfd-online.com/Forums/fluent-udf/79358-1-7-prandtle-velocity-profile.html How to get the gradient of species mass fraction? http://www.cfd-online.com/Forums/fluent-udf/79318-how-get-gradient-species-mass-fraction.html Thu, 19 Aug 2010 16:47:26 GMT Dear my friends. I want to get access to the gradient of species mass fractions. The manual said that the macro C_YI_G(c,t,i) can be used only in... Dear my friends.

I want to get access to the gradient of species mass fractions. The manual said that the macro C_YI_G(c,t,i) can be used only in the density-based solver. To use this in the pressure-based solver, you will need to set the rpvar 'species/save-gradients? to #t. What does that means? How can I set the "rpvar"? Since I know nothing about the scheming languages, can someone give me an example of how to set the rpval in my UDFs?

Thanks a lot. ]]> Fluent UDF and Scheme Programming legendyxg http://www.cfd-online.com/Forums/fluent-udf/79318-how-get-gradient-species-mass-fraction.html where is the mistake? http://www.cfd-online.com/Forums/fluent-udf/79304-where-mistake.html Thu, 19 Aug 2010 10:43:46 GMT Hello,

I want to have a static pressure profile at the outlet for a 2D calculation. For the boundary "outlet" there is y=const. when I use the following UDF, I do get a parabolic profile. But the problem is, at starting point (x=0) and end point, I don't have p=0. so that is not the exact curve I am expecting. I always check through "xy plot" afte initializing over inlet.

So, does anybody know where the problem is?

#include "udf.h"

DEFINE_PROFILE(pressure_profile,t,i)
{
real x[ND_ND];
real a;
face_t f;

begin_f_loop(f,t)
{

F_CENTROID(x,f,t);
a = x[0];
F_PROFILE(f,t,i) = 2.435e5 - (a-0.025)*(a-0.025)/(0.025*0.025)*2.435e5;
}
end_f_loop(f,t)
} ]]> Fluent UDF and Scheme Programming mehendis http://www.cfd-online.com/Forums/fluent-udf/79304-where-mistake.html