hi this is the udf for arbitary drag force from fluent users.com /* Arbitrary Drag coefficients for mixture multiphase model */

/* This may FAIL for MOVING reference frames and zones -- not tested!! */

/* This text offers three drag coefficients, marked by mx, my, mz. */ /* They are calculated using the following general form: % % c_D = c_{D0} + 1.0 * 24 / Re + 6.0 / (1. + sqrt(Re)) % | | | % my_cd my_fd my_tt % % Above are shown the RP variables bound to the parameters. */

/* Before using this, please enter the following in FLUENT6:

(rp-var-define 'mx-cd 0.7 'real #f) (rp-var-define 'mx-fd 1. 'real #f) (rp-var-define 'mx-tt 6. 'real #f) (rp-var-define 'my-cd 0.5 'real #f) (rp-var-define 'my-fd 1. 'real #f) (rp-var-define 'my-tt 6. 'real #f) (rp-var-define 'mz-cd 10. 'real #f) (rp-var-define 'mz-fd 1. 'real #f) (rp-var-define 'mz-tt 6. 'real #f)

(rp-var-define 'joslip-first-udm-in-use 0 'int #f)

Set individual variables using...

(rpsetvar 'my_fd 1.) etc.

Check variables using...

(rpgetvar 'my_fd) etc. ********************************** */

#include "udf.h"

#ifdef INTERPRETER Source code level macro naming problem with "INTERPRETER"...! #endif #ifdef PRINT Source code level macro naming problem with "PRINT"...! #endif #ifdef MyError Source code level macro naming problem with "MyError"...! #endif

#ifdef STRUCT_REF #define INTERPRETER 1 #define PRINT printf #define MyError PRINT #define Boolean int /* Interpreter doesn't accept char here... */ #else #define INTERPRETER 0 #define PRINT CX_Message #define MyError Error #endif

/* Original in mem.h: */ /* #define C_TYPE(c,t)C_STORAGE(c,t,SV_TYPE,uchar_fl *) */ /* This is used in c_face_loop and causes the interpreter to complain: */ /* "non-integer subscript expression: unsigned char" */ /* Therefore, I'm trying a re-definition -- I DON't know if this works! */ #if INTERPRETER #undef C_TYPE #define C_TYPE(c,t)C_STORAGE(c,t,SV_TYPE,int *) #endif

/* ================================ */

int joslip_first_udm_in_use = 32000;

real mx_cd = 0.; real mx_fd = 0.; real mx_tt = 0.; real my_cd = 0.; real my_fd = 0.; real my_tt = 0.; real mz_cd = 0.; real mz_fd = 0.; real mz_tt = 0.;

real drift_relax = 0.;

#if INTERPRETER int degas_warnNudm_done = 0; #endif

void degas_checkNudm(int minimum_number) { /* Check number of allocated User Defined Memory Locations..: */ #if ! INTERPRETER if (sg_udm < minimum_number)

{

Error("Please allocate at least %d User Defined Memory Locations!\n",

minimum_number);

} #else if (! degas_warnNudm_done)

{

PRINT( "Make sure you have allocated at least %d User Defined Memory Locations..\n",

minimum_number);

degas_warnNudm_done = 1;

} #endif }

DEFINE_ADJUST(adjust_myslip, domain) { Thread *t, *subt; Domain *subd; cell_t c; int phind;

joslip_first_udm_in_use = RP_Get_Integer("joslip-first-udm-in-use");

for (subd = DOMAIN_SUB_DOMAIN(domain,(phind=0)); NNULLP(subd);

subd = DOMAIN_SUB_DOMAIN(domain,(++phind))) /*..*/

;

degas_checkNudm(ND_ND * phind + joslip_first_udm_in_use);

mx_cd = RP_Get_Real("mx-cd"); mx_fd = RP_Get_Real("mx-fd"); mx_tt = RP_Get_Real("mx-tt"); my_cd = RP_Get_Real("my-cd"); my_fd = RP_Get_Real("my-fd"); my_tt = RP_Get_Real("my-tt"); mz_cd = RP_Get_Real("mz-cd"); mz_fd = RP_Get_Real("mz-fd"); mz_tt = RP_Get_Real("mz-tt");

drift_relax = RP_Get_Real("drift/relax");

thread_loop_c(t, domain)

{

for (subt = THREAD_SUB_THREAD(t,(phind=0)); NNULLP(subt);

subt = THREAD_SUB_THREAD(t,(++phind))) /*..*/

{

begin_c_loop(c,subt)

{

ND_SET(C_UDMI(c,t,phind * ND_ND + 0 + joslip_first_udm_in_use),

C_UDMI(c,t,phind * ND_ND + 1 + joslip_first_udm_in_use),

C_UDMI(c,t,phind * ND_ND + 2 + joslip_first_udm_in_use),

C_U(c,subt),

C_V(c,subt),

C_W(c,subt));

}

end_c_loop(c,subt)

}

} }

void m_slip(cell_t cell, Thread *mxtr_thrd, int scnd_clmn, int frst_clmn,

real (*fd_function)(real), real *rslt_vect) { Thread *scnd_thrd = THREAD_SUB_THREAD(mxtr_thrd, scnd_clmn); Thread *frst_thrd = THREAD_SUB_THREAD(mxtr_thrd, frst_clmn);

/* FiRST is the dispersed (granular) phase, SeCoND is the primary phase. */ /* The numbering refers to the phase columns in the "Interaction" panel. */

/*real diam = generic_property(cell, frst_thrd, %**** DOMAIN_PROPERTY(THREAD_DOMAIN(frst_thrd)), PROP_diameter, 293.); *** */ real diam = C_PHASE_DIAMETER(cell, frst_thrd); real diaQ = diam * diam; real NV_VEC(slipVel), velo, Re, f_d, tau; real ND_VEC(a_x, a_y, a_z);

real ND_VEC(*frstU, *frstV, *frstW),

ND_VEC(*scndU, *scndV, *scndW); real NV_VEC(torelax); real minus_relax = 1. - drift_relax;

if (0. == drift_relax)

{

MyError("m_slip(): drift_relax may not be zero..!\n");

}

ND_SET(frstU, frstV, frstW,

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

frst_clmn * ND_ND + 0 + joslip_first_udm_in_use),

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

frst_clmn * ND_ND + 1 + joslip_first_udm_in_use),

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

frst_clmn * ND_ND + 2 + joslip_first_udm_in_use));

ND_SET(scndU, scndV, scndW,

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

scnd_clmn * ND_ND + 0 + joslip_first_udm_in_use),

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

scnd_clmn * ND_ND + 1 + joslip_first_udm_in_use),

T_STORAGE_R_XV(mxtr_thrd, SV_UDM_I,

scnd_clmn * ND_ND + 2 + joslip_first_udm_in_use));

/* Calculate "momentum accelaration"

(acceleration due to "convective change")

due to flow cross section variation: */ ND_VEC( a_x = NVD_DOT(C_U_G(cell,mxtr_thrd), C_U(cell,mxtr_thrd),

C_V(cell,mxtr_thrd),

C_W(cell,mxtr_thrd)), a_y = NVD_DOT(C_V_G(cell,mxtr_thrd), C_U(cell,mxtr_thrd),

C_V(cell,mxtr_thrd),

C_W(cell,mxtr_thrd)), a_z = NVD_DOT(C_W_G(cell,mxtr_thrd), C_U(cell,mxtr_thrd),

C_V(cell,mxtr_thrd),

C_W(cell,mxtr_thrd))); /* Is the negative sign correct??? No, it wasn't -- cancelled...! */ /* This should be tested by looking at a bubbly multi-phase flow */ /* that experiences some horizontal acceleration (rotation...!) */

/* Add gravity term...: */

if (M_gravity_p)

{

ND_V(a_x, a_y, a_z, -=, M_gravity);

}

/* Add unsteady term... */

if (rp_unsteady)

{

real physical_time_step = RP_Get_Real("physical-time-step");

ND_DS(a_x, a_y, a_z, +=, C_U(cell,mxtr_thrd) - C_U_M1(cell,mxtr_thrd),

C_V(cell,mxtr_thrd) - C_V_M1(cell,mxtr_thrd),

C_W(cell,mxtr_thrd) - C_W_M1(cell,mxtr_thrd),

/, physical_time_step);

/* Is the negative sign (in "-=") correct? No, it wasn't -- changed. */

}

/* Now, the complete accelaration is in (a_x,a_y,a_z). */ /* Next, calculate the particle relaxation time...: */

/* Calculate [old] slip velocity in order to calculate Reynolds number: */ /* Phase velocities are not available at the time when this runs...! */ /*NV_DD(V, =, C_U(cell, frst_thrd), C_V(cell, frst_thrd), C_W(cell, frst_thrd), %% -, C_U(cell, scnd_thrd), C_V(cell, scnd_thrd), C_W(cell, scnd_thrd)); */ NV_DD(slipVel, =, frstU[cell], frstV[cell], frstW[cell],

-, scndU[cell], scndV[cell], scndW[cell]);

/* Build magnitude of [old] slip velocity: */

velo = NV_MAG(slipVel);

/* Calculated Reynolds number with this [old] slip velocity magnitude: */

Re = RE_NUMBER(C_R(cell, scnd_thrd), velo, diam, C_MU_L(cell, scnd_thrd));

/* Some definitions of drag coefficients..: */ /* Laminar is: C_D = 24. / Re */ /* Turbulent : C_D = const. */ /* we define : f_d = C_D * Re / 24. --- Thus..: */ /* Laminar is: f_d = 1. */ /* Turbulent : f_d ~ Re / 24. */

f_d = (*fd_function)(Re);

/*f_d = (mycd + mytt / (1 - sqrt(Re))) * Re / 24. + myfd;*/

/* (mycd, mytt, and myfd are taken from user settings..) */

/* Now calculate the particle relaxation time for the mixture model: */ /* (This has a different definition than the general part. rel. time!) */

tau = (C_R(cell,mxtr_thrd) - C_R(cell,frst_thrd)) * diaQ /*..*/

/ (18. * C_MU_L(cell,scnd_thrd) * f_d);

/* With this,...: d u_p / d t = 1/tau * (u - u_p) */

NV_DS(torelax, =, a_x, a_y, a_z, *, tau);

NV_VS_VS(rslt_vect, =, torelax, *, drift_relax, +, slipVel, *, minus_relax); }

real schiller_fd_func(real Re) { if (Re > 1000.)

{

return 0.44 * Re / 24.;

} else

{

return (1. + 0.15 * pow(Re, 0.687));

} }

DEFINE_VECTOR_EXCHANGE_PROPERTY(schi_slip, cell, mxtr_thrd, scnd_clmn, frst_clmn, rslt_vect) { m_slip(cell, mxtr_thrd, scnd_clmn, frst_clmn, schiller_fd_func, rslt_vect); }

real unity_fd_func(real Re) { return 1.; }

DEFINE_VECTOR_EXCHANGE_PROPERTY(unit_slip, cell, mxtr_thrd, scnd_clmn, frst_clmn, rslt_vect) { m_slip(cell, mxtr_thrd, scnd_clmn, frst_clmn, unity_fd_func, rslt_vect); }

real mx_fd_func(real Re) { return (mx_cd + mx_tt / (1 - sqrt(Re))) * Re / 24. + mx_fd; }

DEFINE_VECTOR_EXCHANGE_PROPERTY(mxslip, cell, mxtr_thrd, scnd_clmn, frst_clmn, rslt_vect) { m_slip(cell, mxtr_thrd, scnd_clmn, frst_clmn, mx_fd_func, rslt_vect); }

real my_fd_func(real Re) { return (my_cd + my_tt / (1 - sqrt(Re))) * Re / 24. + my_fd; }

DEFINE_VECTOR_EXCHANGE_PROPERTY(myslip, cell, mxtr_thrd, scnd_clmn, frst_clmn, rslt_vect) { m_slip(cell, mxtr_thrd, scnd_clmn, frst_clmn, my_fd_func, rslt_vect); }

real mz_fd_func(real Re) { return (mz_cd + mz_tt / (1 - sqrt(Re))) * Re / 24. + mz_fd; }

DEFINE_VECTOR_EXCHANGE_PROPERTY(mzslip, cell, mxtr_thrd, scnd_clmn, frst_clmn, rslt_vect) { m_slip(cell, mxtr_thrd, scnd_clmn, frst_clmn, mz_fd_func, rslt_vect); }

its given b4 using this enter the following in fluent..do we need to type this all

where to hook these all define vector exchange property in fluent

thanks

[niravtm007]

Hi friends i have cubical section it has two inlets one rectangular & other circular. i need to apply udf for circular inlet only. i am new to using udf's can one please tell how to use it on fluent.
i am working on two cases
1) inlet velocity with parabolic variation (space variation)
2) inlet velocity with sinusodial variation ( time variant)
please help me.