[2022821110240]

I want to compute OSI and RRT by udf in the fluent. I use the code which writed by the khuti in this forum, However, the influence of initial conditions on the calculation results must be taken into account, I need to compute the OSI and RRT for the second artery cycle. In my compute model, the pysical time step is 0.005s, the total compute time is 1s, arterial cycle is 0.5s. the code can work, but the results of OSI and RRT is not the results for the second cycle, any suggestions/helps will appreciate. the code is following:

/************************************************** ****
Oscillatory shear index
************************************************** ****/
#include "udf.h"
#include "math.h"
#include "storage.h"
#include "sg_udms.h"

#define domain_ID 1
#define zone_ID 16

/* Define Names for the WSS UDMI and its components */
DEFINE_EXECUTE_ON_LOADING(nameinit, libudf)
{
Set_User_Memory_Name(0, "uWSS");
Set_User_Memory_Name(1, "uWSSx");
Set_User_Memory_Name(2, "uWSSy");
Set_User_Memory_Name(3, "uWSSz");
Set_User_Memory_Name(4, "OSI");
Set_User_Memory_Name(5, "Timme0");
Set_User_Memory_Name(6, "Timme1");
Set_User_Memory_Name(7, "Timme2");
Set_User_Memory_Name(8, "RRT");
Set_User_Memory_Name(9, "area");
}


/* Initialize the UDM value to zero in complete domain */
DEFINE_INIT(meminit,domain)
{
Thread *c_thread;
cell_t c;

thread_loop_c(c_thread,domain)
{
begin_c_loop(c, c_thread)
{
C_UDMI(c,c_thread,0)= 0;
C_UDMI(c,c_thread,1)= 0;
C_UDMI(c,c_thread,2)= 0;
C_UDMI(c,c_thread,3)= 0;
C_UDMI(c,c_thread,4)= 0;
C_UDMI(c,c_thread,5)= 0;
C_UDMI(c,c_thread,6)= 0;
C_UDMI(c,c_thread,7)= 0;
C_UDMI(c,c_thread,8)= 0;
}
end_c_loop(c, c_thread)
}
}

/* Calculate wall shear stress and store them in UDM */
DEFINE_EXECUTE_AT_END(OSI)
{
Domain *domain;
real area;
face_t f;
real A[ND_ND];
cell_t c, c0;
Thread *t,*t0, *c_thread;
real wallshear [ND_ND];
real Timme [ND_3], Timme0,Timme1,Timme2;
domain = Get_Domain(domain_ID);
Timme0 = 0;
Timme1 = 0;
Timme2 = 0;
Timme0= RP_Get_Real("flow-time");
Timme1= RP_Get_Real("physical-time-step");
Timme2= RP_Get_Integer("time-step");
t = Lookup_Thread(domain,zone_ID);
if (Timme0 >=0.5)
begin_f_loop(f, t)
{
F_AREA(A,f,t);
area = NV_MAG(A);
NV_V(wallshear,=,F_STORAGE_R_N3V(f,t, SV_WALL_SHEAR));
c0 = F_C0(f,t);
t0 = THREAD_T0(t);
C_UDMI(c0,t0,0) += NV_MAG(wallshear)/area;
C_UDMI(c0,t0,1) += -wallshear[0]/area;
C_UDMI(c0,t0,2) += -wallshear[1]/area;
C_UDMI(c0,t0,3) += -wallshear[2]/area;
C_UDMI(c0,t0,4) = (1 - sqrt(C_UDMI(c0,t0,1)*C_UDMI(c0,t0,1) + C_UDMI(c0,t0,2)*C_UDMI(c0,t0,2) + C_UDMI(c0,t0,3)*C_UDMI(c0,t0,3))/C_UDMI(c0,t0,0))/2;
C_UDMI(c0,t0,5) = Timme0;
C_UDMI(c0,t0,6) = Timme1;
C_UDMI(c0,t0,7) = Timme2;
C_UDMI(c0,t0,8) = Timme0/sqrt(C_UDMI(c0,t0,1)*C_UDMI(c0,t0,1) + C_UDMI(c0,t0,2)*C_UDMI(c0,t0,2) + C_UDMI(c0,t0,3)*C_UDMI(c0,t0,3));
C_UDMI(c0,t0,9) = area;
}
end_f_loop(f,t)
end if
}

[mep20108@tezu.ac.in]

Hi,
I have checked your code the RRT not gives accurate results even for one cycle. It gives value under 0.5 only. I think the expression of RRT which you stored in UDM 8 is not correct. Please check.
C_UDMI(c0,t0,8) = Timme0/sqrt(C_UDMI(c0,t0,1)*C_UDMI(c0,t0,1) + C_UDMI(c0,t0,2)*C_UDMI(c0,t0,2) + C_UDMI(c0,t0,3)*C_UDMI(c0,t0,3));

If you solve your problem. please post updated code.

Thanking you
Asif