## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### FLUENT Boundary conditions UDF (heat flux – convective losses – rediation losses), error

• 100041488
Subscriber
Hi folks,nI am creating my first UDF and I have a problem, I do not understand how to read the face wall temperature n. Can anyone help me?. The code is almost ready except how to input this temperature. Many thanks in advance.nPS: If i set up temperature at 500 K all calculus are ok, but I would need to read the real one!nn#include udf.hn#define QMAX 407400 /* W/m2 */n#define EEPSILON 0.1n#define TAU 5.67e-8n#define T_AIRE 300n#define H_AIRE 40 /* convective coef.W/m2K */nn/* profile for heat flux*/nDEFINE_PROFILE(heatflux_profile, t, i)nn{n/* variable declaration */nreal centroide[ND_ND]; /* vector position */nreal x;nreal y;nface_t f;ncell_t cell;nreal seno; /* heat distribution */nreal T_p; /* wall temperature */begin_f_loop(f, t)n{nF_CENTROID(centroide,f,t);nx=centroide[0]; /* valor del cntroide en la componente x */ny=centroide[1]; /* valor del cntroide en la componente y */nseno=y/sqrt((x*x)+(y*y));T_p = 500; /* I NEED TO FIND THE FUNCTION IN ORDER TO READ THE WALL TEMPERATURE, DO NOT WHY F_T(f,t) DOES NOT WORK, it should be  T_p = F_T(f,t) */nnif (0 < y)n{nF_PROFILE(f,t,i)=(QMAX*seno)-TAU*((T_p*T_p*T_p*T_p )-(EEPSILON*T_AIRE*T_AIRE*T_AIRE*T_AIRE))-H_AIRE*(T_ p-T_AIRE);nn} else {nF_PROFILE(f,t,i)=0;n}n}nend_f_loop(f, t)n}n
• Karthik R
Administrator
Hello,nLooks like there are a few typos in your UDF syntax such as 'Centroide' Please see some of the UDFs available in this link below. You should be able to use F_T(f,t)nSince you are using an analytical expression, you should also be able to use Fluent expressions here. nThank you.nKarthikn
• 100041488
Subscriber
Hi, thanks for the feedback, the problem was the mesh, below is the final UDF (and it works)n#include udf.hn#define QMAX 407400 /* W/m2 */n#define EEPSILON 0.9n#define TAU 5.67e-8n#define T_AIRE 300n#define H_AIRE 40nn/* profile for heat flux*/nDEFINE_PROFILE(receiver, t, i)nn{n /* declaración de variables */nreal centroide[ND_ND]; /* vector de posición */nreal x;nreal y;nface_t f;ncell_t cell;nreal seno; /* para meter la distribucion de calor */nreal T_p; /* temperatura de la pared */begin_f_loop(f, t)n{nF_CENTROID(centroide,f,t);nx=centroide[0]; /* valor del cntroide en la componente x */ny=centroide[1]; /* valor del cntroide en la componente y */nseno=y/sqrt((x*x)+(y*y));T_p=F_T(f,t); if (0 < y)n{ntF_PROFILE(f,t,i)=(QMAX*seno)-TAU*((T_p*T_p*T_p*T_p)-(EEPSILON*T_p*T_p*T_p*T_p))-H_AIRE*(T_p-T_AIRE);ntn} else {ntF_PROFILE(f,t,i)=0;n}n}n
• Karthik R
Administrator
Perfect !! Good to know!n
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