[iceman53y]

Hi,

I am new to Fluent.
I am trying to oscillate a wall at a certain frequency in the horizontal direction.

It is a circular tube that I am trying to oscillate and see the effect of the lift and drag forces on the adjacent tubes at different flow velocities of water.

Some people have told me about UDFs. I don't know how to do that.

If there is an easier way please let me know or please walk me through creating a UDF.

Appreciate your help.

kind regards,

CFD noob.

[LuckyTran]

Is the oscillation parallel to the flow? I.e. is there any squeezing effect?

You can just apply a time-dependent velocity to the wall. The velocity can be applied as a udf or even simpler a csv style profile.

[iceman53y]

Hi,

I've managed to start compiling UDFs without any issues now. Took me two days to get it working.

Appreciate if someone can share a UDF for oscillating a cylinder in cross flow at a certain frequency from its current location.

There is no squeezing effect.

Thanks

[iceman53y]

Hi,

I've managed to start compiling UDFs without any issues now. Took me two days to get it working.

Appreciate if someone can share a UDF for oscillating a cylinder in cross flow at a certain frequency from its current location.

There is no squeezing effect.

Thanks

[iceman53y]

Hi,

This UDF is working but the cylinder moves to the right and comes back to same position, therefore is oscillating about a point towards the right of the origin point of the cylinder. I want it to oscillate right and left from its current location.

How would I change this code?

Please help.

/* Moving Grid problem - CG movement of a cylinder */
#include "udf.h"
static real velx = 0.0;
DEFINE_CG_MOTION(cylinder, dt, vel, omega, time, dtime)
{
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);

velx = 0.005 * sin(3.1415927 * time / 5.);
vel[0] = velx;
}