[Zerzura]

Good day all,

I would like to implement an Anisotropic Diffusivity for my UDS in a cylinder. This is actually mimicking a drug that is distributing in the arterial wall.
There was a nice example in the UDF manual 12.0 how to do this, unfortunately this does not work in my fluent program and I do not know why. There is already a error message for line 4.
Can somebody please help me?
(I do not know exactly what line 4 and 5 do)

I really appreciate your help!
Have a good day.

UDF:

#include "udf.h"

/* computation of anisotropic diffusivity matrix for cylindrical orthotropic diffusivity */
static const real origin[3] = {0.0, 0.0, 0.0};
static const real axis[3] = {0.0, 0.0, 1.0};

DEFINE_ANISOTROPIC_DIFFUSIVITY(cylc_diff,c,t,i,dma trix)
{
real x[3][3];
real xcent[ND_ND];
real R;
/*diffusivities in radia, tangential and axial directions */
real dd1, dd2, dd3;
dd1 = 3e-14*C_R(c,t);
dd2 = 7e-11*C_R(c,t);
dd3 = 7e-11*C_R(c,t);

static const real diff[3] = {dd1,dd2,dd3};

C_CENTROID(xcent,c,t);

NV_VV(x[0],=,xcent,-,origin);
#if RP_3D
NV_V(x[2],=,axis);
#endif
#if RP_3D
R = NV_DOT(x[0],x[2]);
NV_VS(x[0],-=,x[2],*,R);
#endif
R= NV_MAG(x[0]);
if (R>0.0)
NV_S(x[0],/=,R);
#if RP_3D
N3V_CROSS(x[1],x[2],x[0]);
#else
x[1][0] = -x[0][1];
x[1][1] = x[0][0];
#endif

dmatrix[0][0] = diff[0]*x[0][0]*x[0][0]+diff[1]*x[1][0]*[1][0]
#if RP_3D
+diff[2]*x[2][0]*x[2][0]
#endif
;
dmatrix[1][1]=diff[0]*x[0][1]*x[0][1]
+diff[1]*x[1][1]*x[1][1]
#if RP_3D
+diff[2]*x[2][1]*x[2][1]
#endif
;
dmatrix[1][0] = diff[0]*x[0][1]*x[0][0]
+diff[1]*x[1][1]*x[1][0]
#if RP_3D
+diff[2]*x[2][1]*[2][0]
#endif
;
dmatrix[0][1] = dmatrix[1][0];

#if RP_3D
dmatrix[2][2] =diff[0]*x[0][2]*x[0][2]
+diff[1]*x[1][2]*x[1][2]
+diff[2]*x[2][2]*x[2][2]
;
dmatrix[0][2] = diff[0] *x[0][2]*x[0][2]
+diff[1]*x[1][0]*x[1][2]
+diff[2]*x[2][0]*x[2][2]
;
dmatrix[2][0] =dmatrxi[0][2];

dmatrix[1][2] = diff[0] *x[0][1]*x[0][2]
+diff[1]*x[1][1]*x[1][2]
+diff[2]*x[2][1]*x[2][2]
;
dmatrix[2][1] =dmatrxi[1][2];
#endif
}

[ssss]

There is a bug in your code, dmatrxi[1][2] should be dmatrix

[Zerzura]

I am sorry for my late reply!
Thank you for your answer, you are indeed correct! However I changed my method and no longer need this UDF.

Kind regards, and thanks again!