[PXY]

Hello everyone, I am learning Fluent, but I have a problem:
Can UDF get the value of another cell? For example, I want to define the viscosity of the cell, but I need to use the value of the cell adjacent to the wall. The line between these two points is perpendicular to the wall. I tried using Looping macros in DEFINE_PROPERTY Macros, or looping each cell in DEFINE_ADJUST Macro and then nested loops inside to get the value of the wall adjacent cell, but running would show: Received signal SIGSEGV. Is it because UDFs can't nest with loops?
Thank you very much！
here is my code

[PXY]

[CODE]
#include"udf.h"
#include"mem.h"
#define F 0.4
#define B 500
#define g 9.81
#define h 0.3
#define l 0.0051

DEFINE_ADJUST(adjust, d)
{
#if !RP_HOST
Thread* t;
cell_t c;
face_t f;
real x[ND_ND], xc[ND_ND];
real a;
int ID1 = 11, ID2 = 35;
Thread* t1 = Lookup_Thread(d, ID1);
Thread* t2 = Lookup_Thread(d, ID2);
thread_loop_c(t, d)
{
begin_c_loop(c, t)
{
if (C_VOF(c, t) >= 0.70)
{
C_CENTROID(x, c, t);
if ((x[1] - x[0]) / 2 > -h)
{
a = (x[1] - x[0]) / 2;
begin_f_loop(f, t1)
{
Thread* t0 = THREAD_T0(t1);
cell_t c0 = F_C0(f, t1);
C_CENTROID(xc, c0, t0);
if (sqrt(pow((xc[1] - a), 2) + pow((xc[0] + a), 2)) < l)
{
C_UDMI(c, t, 1) = C_UDMI(c0, t0, 0);
}
}
end_f_loop(f, t1)

begin_f_loop(f, t2)
{
Thread* t0 = THREAD_T0(t2);
cell_t c0 = F_C0(f, t2);
C_CENTROID(xc, c0, t0);
if (sqrt(pow((xc[1] + h), 2) + pow((xc[0] - x[0]), 2)) < l)
{
C_UDMI(c, t, 1) = C_UDMI(c0, t0, 0);
}
}
end_f_loop(f, t2)
}
else
{

begin_f_loop(f, t2)
{
Thread* t0 = THREAD_T0(t2);
cell_t c0 = F_C0(f, t2);
C_CENTROID(xc, c0, t0);
if (sqrt(pow((xc[1] - a), 2) + pow((xc[0] + a), 2)) < l)
{
C_UDMI(c, t, 1) = C_UDMI(c0, t0, 0);
}
}
end_f_loop(f, t2)
}

}
}
end_c_loop(c, t)
}
#endif /* only compute nodes are involved */
}
[CODE]