[KHAN REHAN WASIM]

I encountered the following error "temperatuejump.c: line 66: coord_coeff: undeclared variable" while solving the problem using the code mention below

/* ================================================== ======
Temperature change at wall boundaries
================================================== ==== */
#include "udf.h" /* must be at the beginning of every UDF */
#include "sg.h" /*must be at the beginning of this UDF */
#include "math.h" /* must be at the beginning of this UDF */

# ifndef SCHEMESIGMASQUARE
# define sigma_square 1.35305239e-19
# endif
# ifndef SCHEMEAMPRESS
# define ambpress 101325
# endif

# ifndef SCHEMETMAC
# define TMAC 1.0
# endif
# ifndef SCHEMEThAC
# define ThAC 1.0
# endif
# ifndef SCHEMESpHR
# define SpHR 1.4

# endif

# ifndef SCHEMEUDRLXCOEFF
# define UDRLXCOEFF 0.02
# endif

# define Boltzmann 1.3806505e-23
# define PI 3.14159265358979323846
# define SQRT_2 1.41421356237309504880

DEFINE_PROFILE(temperature_jump,f_thread,index)
{
real MeanFreePath;
#ifdef SCHEMEMFP
MeanFreePath=RP_Get_Real("meanfreepath");
#endif

#ifdef SCHEMEThAC
real ThAC= 1;
ThAC=RP_Get_Real("thac");
#endif

#ifdef SCHEMEUDRLXCOEFF
real UDRLXCOEFF=O.2;
UDRLXCOEFF=RP_Get_Real("udrlxcoeff");
#endif

#ifdef SCHEMESpHR
real SpHR;
SpHR=RP_Get_Real("sphr");
#endif

face_t face;
cell_t cell;

Thread*c_thread;

real Coeff2[ND_ND];

real Prandtl,gamma,temp,normal;

/* call the routine that computes the transformation coefficients, once per iteration should be enough*/
coord_coeff(f_thread);

/* loops over all faces in the thread passed into the DEFINE macro argument */

begin_f_loop(face,f_thread);

{
cell=F_C0(face,f_thread);
c_thread=THREAD_T0(f_thread);

#ifndef SCHEMEMFP
MeanFreePath = Boltzmann*F_T(face,f_thread)/(sigma_square*(F_P(face,f_thread)+ambpress)* PI*SQRT_2);

#endif

Prandtl=(C_MU_L(cell,c_thread)*C_CP(cell,c_thread) )/C_K_L(cell,c_thread);

ND_SET(Coeff2[0],Coeff2[1],Coeff2[2],
F_UDMI(face,f_thread,3),
F_UDMI(face,f_thread,4),
F_UDMI(face,f_thread,5));

/* evaluate the dT/dn (normal to surface) term in the local coord. system */

normal=NV_DOT(Coeff2,C_T_G(cell,c_thread));

gamma=(2*SpHR)/(SpHR+1);
temp=((2-ThAC)/ThAC)*gamma*
MeanFreePath/Prandtl*normal;
/* in order to set wall temperature a user definedd scalar variahle F_UDSI( ....,0) has to be created (its transport is not important and won't effect ths result)*/

#ifdef UNDERRLX

F_PROFILE(face,f_thread,index)=
F_T(face,f_thread)*(l-UDRLXCOEFF)+
(F_UDSI(face,f_thread,0)+temp);
#else

F_PROFILE(face,f_thread,index)=(F_UDSI(face,f_thre ad,0)+temp);

#endif

}
end_f_loop(f,thread)

}

void coord_coeff(Thread *f_thread)
{
face_t face;
cell_t cell;
Thread *c_thread;
real y[ND_ND];
real u[ND_ND],a;
real A[ND_ND];
real dr0[ND_ND],es[ND_ND],ds,A_by_es;

begin_f_loop(face,f_thread)
{
F_CENTROID(y,face,f_thread);
cell=F_C0(face,f_thread);
c_thread=THREAD_T0(f_thread);

BOUNDARY_FACE_GEOMETRY(face,f_thread,A,ds,es,A_by_ es,dr0);

ND_SET(u[0],u[1],u[2],
C_U(face,f_thread),
C_V(face,f_thread),
C_W(face,f_thread));
a=NV_MAG(u);

ND_SET(F_UDMI(face,f_thread,0),
F_UDMI(face,f_thread,1),
F_UDMI(face,f_thread,2),
NVD_DOT(u,1,0,0)/a,
NVD_DOT(u,0,1,0)/a,
NVD_DOT(u,0,0,1)/a);

ND_SET(F_UDMI(face,f_thread,3),
F_UDMI(face,f_thread,4),
F_UDMI(face,f_thread,5),
NVD_DOT(A,1,0,0)/A_by_es,
NVD_DOT(A,0,1,0)/A_by_es,
NVD_DOT(A,0,0,1)/A_by_es);
}

end_f_loop(face,f_thread)

}

I will be grateful if someone can help in solving the issue

[msaeedsadeghi]

send this function (void coord_coeff) to top of (DEFINE_PROFILE) function.
I have modeled microchannel flow before

[Soner_isik]

Hi Guys

I am trying to use UDF given above for simulating temperature jump in a micro channel. as I understood, 1 user defined scalar and 6 user defined memory units should be allocated before assigning UDF to wall temp. but when I try to use it as thermal BC, fluent gives me Fatal Signal received access violation.what should I do?

please help me
Regards
Soner

[MichaelChan]

Originally Posted by Soner_isik

Hi Guys

I am trying to use UDF given above for simulating temperature jump in a micro channel. as I understood, 1 user defined scalar and 6 user defined memory units should be allocated before assigning UDF to wall temp. but when I try to use it as thermal BC, fluent gives me Fatal Signal received access violation.what should I do?

please help me
Regards
Soner

I don't know how to use F_UDSI for temperature.
Could you help me?
Thx in advance

[zhangdongjie]

Originally Posted by msaeedsadeghi

send this function (void coord_coeff) to top of (DEFINE_PROFILE) function.
I have modeled microchannel flow before

Hello, I'm studying wall slip and temperature jump. Would you please send me a UDF? Thank you very much. In addition, where is the temperature jump UDF loaded? Is it on the wall temperature?thanks。

[pakk]

Originally Posted by zhangdongjie

Hello, I'm studying wall slip and temperature jump. Would you please send me a UDF? Thank you very much. In addition, where is the temperature jump UDF loaded? Is it on the wall temperature?thanks。

1. The UDF is shown in the first post.
2. You don't need this UDF (anymore), just use pressure based over and use low - pressure - boundary - slip. It has temperature jump, read the manual.

[zhangdongjie]

Originally Posted by pakk

1. The UDF is shown in the first post.
2. You don't need this UDF (anymore), just use pressure based over and use low - pressure - boundary - slip. It has temperature jump, read the manual.

Thank you very much for your reply. Low - pressure - Boundary - slip is only applicable to "pressure based", but I am based on "density based". When I choose "density based" instead of "pressure based". "Low pressure boundary slip" is not available. That's why I choose to use UDF, but I don't know where to load UDF with temperature jump?

[pakk]

Originally Posted by zhangdongjie

Thank you very much for your reply. Low - pressure - Boundary - slip is only applicable to "pressure based", but I am based on "density based". When I choose "density based" instead of "pressure based". "Low pressure boundary slip" is not available. That's why I choose to use UDF, but I don't know where to load UDF with temperature jump?

Solution is extremely simple: don't use density-based!

[zhangdongjie]

Originally Posted by pakk

Solution is extremely simple: don't use density-based!

This is a very good method, but my simulated Mach number is more than 3. If you use "pressure based", it may not be very accurate

[pakk]

Modern pressure-based methods such as implemented in Fluent can do reasonably well with high Mach numbers, there is some benchmarking study in the manual.