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 January 9, 2010, 04:54 Temperature gradient macros on face #1 New Member   qwerty753 Join Date: May 2009 Posts: 16 Rep Power: 10 How to obtain a temperature gradient directly from the solver for the UDF purposes? Does any macro exist to compute temperature gradient on a face? my aim i to extract heat flux on a face! Thank you

March 9, 2010, 00:54
#2
Senior Member

Ji Junjie
Join Date: Feb 2010
Location: Shanghai, China
Posts: 110
Rep Power: 10
Quote:
 Originally Posted by qwerty753 How to obtain a temperature gradient directly from the solver for the UDF purposes? Does any macro exist to compute temperature gradient on a face? my aim i to extract heat flux on a face! Thank you
If your face is a wall boundary, then use WALL_HEAT_FLUX(face_t f,Thread*tf) to directly report the heat flux

 March 11, 2010, 08:35 #3 New Member   qwerty753 Join Date: May 2009 Posts: 16 Rep Power: 10 Thanks, but i don't need of a heat flux, i want to know dt/dn i.e. gradient. Bye.

March 12, 2010, 01:08
#4
Senior Member

Ji Junjie
Join Date: Feb 2010
Location: Shanghai, China
Posts: 110
Rep Power: 10
Quote:
 Originally Posted by qwerty753 How to obtain a temperature gradient directly from the solver for the UDF purposes? Does any macro exist to compute temperature gradient on a face? my aim i to extract heat flux on a face! Thank you
You can define a UDS. loop over all the cells and let its UDS value equal to the temperature gradient , C_UDSI(c,t,0)=C_T_G(c,t).
Then use the UDS gradient on cell, distance vector to compute the temperature gradient on face.

#include "udf.h"
DEFINE_ON_DEMAND(test)
{
face_t f;
cell_t c0;
Domain*domain=Get_Domain(1);
real NV_VEC(dist_vector);
real f_centoid[ND_ND],c_centroid[ND_ND];
real face_value,cell_value;
{
begin_f_loop(f, tf) /* loops over faces in a face thread */
{
F_CENTROID(f_centoid,f,tf); //centroid of a face
c0=F_C0(f,tf);
C_CENTROID(c_centroid,c0,t0); //centroid of the neighbour cell
NV_DD(dist_vector,=,f_centoid[0],f_centoid[1],0,-,c_centroid[0],c_centroid[1],0);
face_value=C_UDSI(c0,t0,0)+NV_DOT(C_UDSI_G(c0,t0,0 ),dist_vector);
cell_value=C_UDSI(c0,t0,0);
Message0("x coord.=%g,face value=%g,cell value=%g\n",f_centoid[0],face_value,cell_value);
}
}
}

 June 16, 2010, 03:38 convective boundary condition #5 New Member   askask Join Date: Jun 2010 Posts: 1 Rep Power: 0 after writing a similar face gradient, i have to give a mass convection boundary condition with the face and air, but i couldn't manage to put the cell (for air) and face (for solid face) together. can you help me?

 March 12, 2013, 08:20 #6 Member   Satish Gupta Join Date: Jun 2012 Posts: 30 Rep Power: 7 I am solving a 2D problem. I want to calculate temperature gradient (and also write it) on the surface(line) whose end points I know. Can anyone tell me how to do it Thank you

 July 31, 2016, 11:13 udf for temperature gradient #7 New Member   saad Join Date: May 2012 Posts: 6 Rep Power: 7 I want x and y component of temperature gradient, please tell me how can i be able to get it. i have done solve/set/expert to retain various gradients. but when i am try to run the simulation fatal error occurs. I am writing my code below. #include "udf.h" DEFINE_ADJUST(my_adjust,domain) { Thread*t; cell_t c; real vol_tot, tavg; tavg=0.; vol_tot=0.; domain=Get_Domain(1); thread_loop_c(t,domain) { begin_c_loop(c,t) { vol_tot += C_VOLUME(c,t); tavg += (C_T(c,t)*C_VOLUME(c,t)); end_c_loop(c,t) } tavg= tavg/vol_tot; printf("Volume integral of temperature:%g\n", tavg); } thread_loop_c(t,domain) { begin_c_loop(c,t) { C_UDMI(c,t,0)=tavg; C_UDSI(c,t,0)= C_T_G(c,t)[0]; } end_c_loop(c,t) } } DEFINE_SOURCE(mom_source,c,t,dS,eqn) { real x[ND_ND]; real source; C_CENTROID(x,c,t); source= 1.0+5.33*(C_T(c,t)-C_UDMI(c,t,0)); dS[eqn]= 0.0; return source; }

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