Compute_Force_And_Moment
 

The problem i want to study is about fluid-structure coupling. In the UDF procedure, force of the cylinder in X and Y direction is calculated respectively by the function " Compute_Force_And_Moment(domain, tf1, CG, force, moment, FALSE)", Then the motion of the body is decided by solving the "m-c-k" differential equations of motion , in which m c k are defined at the beginning.
What's strange is that, in any one instant, force[0] computed in the UDF is quite different from the value obtained in "report-force" calculated by the software itself. However, force[1] by UDF is the same as the value offered by software itself.
From the results, i find the value from "report-force" is resonable, however, force[0] calculated by "Compute_Force_And_Moment" is quite small. I don't know why.
Who could help me solve the problem? Here is the UDF precedure.Thanks!

Hi i am also wrking on the same problem ...have u overcome the above difficulty???