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#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 */
/*Set preprocessor directives here in order to change
behaviour of the routine:*/
#define not SCHEMEMFP /* shall MeanFreePath be scheme var.? */
#define SCHEMETMAC /* shall TMAC ... */
#define SCHEMEUDRLXCOEFF /* shall the under-relaxation
coefficient... */
#define not SCHEMEThAC /* shall ThAC ... */
#define not SCHEMESpHR /* shall SpHR ... */
#define SCHEMESIGMASQUARE /* shall sigma-square value... */
#define SCHEMEAMBPRESS /* shall ambient pressure value... */
34 A. Computational Routine
#define UNDERRLX /* shall slip veloc be under-relaxated in
severe cases? */
#define WALLMOTION /* shall wall-motion be regarded? */
/*
If the scheme variables are not used fall back to some default
values as below, also some constants are defined
*/
#ifndef SCHEMESIGMASQUARE
#define sigma_square 1.35305239e-19 /* squared value of
sigma(molecule diameter) */
#endif
#ifndef SCHEMEAMBPRESS
#define ambpress 101325 /* ambient pressure */
#endif
#ifndef SCHEMETMAC
#define TMAC 1.0 /* tangential momentum accomodation
coefficient */
#endif
#ifndef SCHEMEThAC
#define ThAC 1.0 /* thermal accomodation coefficient */
#endif
#ifndef SCHEMESpHR
#define SpHR 1.4 /* specific heat ratio; Air, Oxygen,
Nitrogen */
#endif
#ifndef SCHEMEUDRLXCOEFF
#define UDRLXCOEFF 0.02 /* under-relaxation coefficient */
#endif
#define Boltzmann 1.3806505e-23 /* Boltzmann constant */
#define PI 3.14159265358979323846 /* number pi */
#define SQRT_2 1.41421356237309504880 /* sqrt(2) */
A.1. Slip Velocity Routine 35


DEFINE_PROFILE(maxwell_slip_velocity_x_full,f_thread,index)
{
#ifdef SCHEMETMAC
real TMAC=1;
TMAC=RP_Get_Real("tmac");
#endif
real MeanFreePath=6.8e-8;
#ifdef SCHEMEMFP
MeanFreePath=RP_Get_Real("meanfreepath");
#endif
#ifdef SCHEMEUDRLXCOEFF
real UDRLXCOEFF=0.2;
UDRLXCOEFF=RP_Get_Real("udrlxcoeff");
#endif
#ifdef SCHEMESIGMASQUARE
real sigma_square=1.0e-19;
sigma_square=RP_Get_Real("sigmasquare");
#endif
#ifdef SCHEMEAMBPRESS
real ambpress;
ambpress=RP_Get_Real("ambpress");
#endif
face_t face;
cell_t cell;
36 A. Computational Routine
Thread *c_thread;
real slip, thcreep, dveloc;
real normal_slip, tangential_slip, tangential_thcreep;
real Coeff1[ND_ND], Coeff2[ND_ND];
real u[ND_ND];
/* call the routine that computes transformation coefficients,
once per iteration is sufficient
coord_coeff(f_thread) is called only in the velocity
$x$-coordinate routine and activated by the coordeval
scheme variable(integer) */
if (RP_Get_Integer("coordeval")==1) coord_coeff(f_thread)
if ((RP_Get_Integer("tempgradeval")>1)&&(Data_Valid_P()))
{
begin_f_loop(face,f_thread)
{
/* get cell and cell thread pointer */
cell=F_C0(face,f_thread);
c_thread=THREAD_T0(f_thread);
/* compute mean free path at every position */
#ifndef SCHEMEMFP
MeanFreePath = Boltzmann * F_T(face,f_thread) / (
sigma_square * (F_P(face,f_thread)+ambpress)*
PI * SQRT_2 ) ;
#endif
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