[bestniaz]

Dear Friends,

Need your help in making code to analyze vortex induced vibration for forced vibration cylinder and free oscillating cylinder in Fluent.
I am beginner in field of UDF and facing a lot of problem. Plz help

Currently, I successfuly simulated once 2D case study using the following UDF.

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 = 0.2;
real wn = 12.0;
real k= mass * wn*wn;
real c = 2*mass*wn*0.00;
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];


I used this UDF and its working. ....In this UDF, it is seem free osciallation ( I think)..
I have 2 very basic question.

1. How to change the above UDF into force oscillation with A=0.3D , A=amplitude and D is Dia of cylinder. In addition, the motion of cylinder is sinusoidal i.e. y(t) =ASin(2*3.14*f*t), and y=crossflow direction, A=amplitude and f=Oscillating frequency of cylinder..........So where should I adjust or add the equation in UDF

2. Reduced Velocity,Ur=U/(fn*D). If I want to perform analysis at Ur=2, Ur=4 and Ur=8. To perform analysis at different Ur, what parameter is required to be modify. All the analysis will be at Re=10,000.

Thanks in advance

Regards
Niaz