[Research_Eva]

Hi everyone,

Hope someone can help me! I'm new to CFD and currently trying to simulate bloodflow in the large arteries around the human heart.

I wrote an UDF defying the mass flow over time during a heartbeat which is intepreted without problems. But when I intitialize the solution I directly get an error saying:

Error: Divergence detected in AMG solver: ads-0
Error Object: #f

Before, with use of another UDF I had no problems. It's with the same anatomy and Mesh so I think the problem is in the UDF and not in the geometry.
Does anyone have tips on how to solve this problem?

Thank you in advance!

This is my current UDF:

// UDF for specifying time dependant mass flow inlet profile boundary condition
// Mass flow inlet with diastolic backflow (regurgitation)

#include "udf.h"//file that contains definitions for define functions and fluent operations
#define PI 3.141592654
#define Systtime 0.67// systolic time 2/3 of whole heartbeat
#define HR 114 // Heart rate (beats/minute)
#define Qmax_mass 0.1582 // maximum mass flow during systole (kg/s)
#define Dystime 0.33//diastolic time 1/3 of whole heartbeat
#define Qmaxd_mass 0.1131 // maximum mass flow (backflow) during diastole (kg/s)

DEFINE_PROFILE(inlet_massflow,th,i)
{
face_t f;
begin_f_loop(f,th)
double t = CURRENT_TIME; //t is the local time within each period

{
if(t <= (1/3)*Systtime*60/HR)
F_PROFILE(f,th,i) = Qmax_mass*sin((0.5*PI/((1/3)*Systtime*60/HR))*t);

if((t <= (27/30)*Systtime*60/HR) && (t > (1/3)*Systtime*60/HR))
F_PROFILE(f,th,i) = Qmax_mass*sin((0.5*PI/((17/30)*Systtime*60/HR))*(t+(7/30)*Systtime*60/HR));

if((t <= (27/30)*Systtime*60/HR+(1/4)*Dystime*60/HR) && (t > (27/30)*Systtime*60/HR))
F_PROFILE(f,th,i) = Qmaxd_mass*-sin((0.5*PI/((1/4)*Dystime*60/HR))*(t-(27/30)*Systtime*60/HR));

else
F_PROFILE(f,th,i) = 0.5*Qmaxd_mass*sin((PI/((3/4)*Dystime*60/HR))*(t-((27/30)*Systtime+(1/4)*Dystime-3*(3/8)*Dystime)*60/HR))-0.5*Qmaxd_mass;
}
end_f_loop(f,th);
}