[Mar777]

Hello guys,
Please, I need help
Can anyone tell me what is the problem next message to appear:

"6DOF object must have positive mass"

After compilation, dynamic mesh options set-up I used next option in Fluent: "Mesh motion/Preview" and the program returned the message above.

Here it is the udf:

#include "udf.h"
DEFINE_SDOF_PROPERTIES(airvehicle, prop, dt, time, dtime)
{
prop[SDOF_MASS] = 90.185;
prop[SDOF_IXX] = 27.116;
prop[SDOF_IYY] = 395.094;
prop[SDOF_IZZ] = 395.094;

}

What is going on, why is this problem??????????????

Thank you very much for your help

[koray]

Hey there,

In such cases which include sdof solver enabled, you shouldn't be able to preview the mesh motion directly. Because, it should require flow field properties to be solved in the first place. You may try to use a simple velocity profile in order to preview mesh motion and check your dynamic mesh settings.

Hope it helps
Koray

[vasava]

It is possible that the box in your domain is not aligned with x,y,z coordinate system. I mean that the Ixx you have may not be applicable to face in x-direction. Similarly Iyy and Izz.

[scurtucristian]

Place the center of gravity of the floatng body coordinates in this path:

Dynamic mesh>Dinamic mesh zones>Center of Gravity

Default is (0,0,0) please put here your corect values.

[Mar777]

Thank you very much for your help! It helped a lot!

[Ahmed Saeed Mansour]

Hello, could you tell me the basics of using the 6 DOF in Fluent? Thanks

[Sachin Zanje]

Hi

Could you please provide details about how to give simple velocity profile and preview the mesh motion when i am getting the error of "6DOF object must have positive mass".

[Ahmed Saeed Mansour]

Hello dear Sachin , watch my tutorial and ask about anything you do not understand, I have shown how to use a udf for the variable velocity at inlet Thanks
https://youtu.be/vrhHs6QbyTU

[Sachin Zanje]

Thank you so much dear Ahmed.

[Ahmed Saeed Mansour]

Originally Posted by Sachin Zanje

Thank you so much dear Ahmed.

Bitte Schön sehr geehrter Sachin!