[Entwistle]

Hello to everybody;

Now I am investigating about VIV using tappered cylinders (3D); I am using 2-way FSI but the calculations are so slow (LES-WALE model in CFD and non-linear calculation in Transient Structural). I really need to do these calculations faster, so I think in use an UDF for VIV.

Searching in the web, I found the next code, originally for a 2D problem:

#include "udf.h"
static real v_prev = 0.0;

DEFINE_CG_MOTION(osc, dt, vel, omega, time, dtime)
{
Thread *t;
Domain *d = Get_Domain(1);
real x_cg[3], force[3], moment[3];
real accl, dv;
real mass = 0.022;
real wn = 3.0;
real k = mass*wn*wn;
real c = 2*mass*wn*0.0; /*no damping*/
int i;

NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);
t = DT_THREAD(dt);
for (i=0;i<3;i++)
x_cg[i]=DT_CG(dt)[i];

Compute_Force_And_Moment(d, t, x_cg, force, moment, TRUE);
force[1] += -k*x_cg[1] - c*vel[1];

accl = -force[1]/mass;
dv = accl*dtime;
v_prev+=dv;
vel[1] = v_prev;
printf("Computed force: %g \n", force[1];
printf("Velocity: %g \n", vel[1]);
}

DEFINE_CG_MOTION(osc_inert, dt, vel, omega, time, dtime)
{
vel[0] = 0.0;
vel[1] = v_prev;
}

First of all, when I try to interpret this UDF in my 3D problem the debugger send me a parse error on the line 2; I think that it is not possible to have any error on this line (I wrote all the code by myself using the original file as a reference, so I think that there is not any syntax bug), so it will be greatfull if any could help me about this point.

The second issue is a simple question: Is it possible to use this code in my 3D problem, or I will have to adapt the code?

Thank you very much.

Bests regards.