[CFD-Henning]

Hey, I'm simulating a floating monopile in a numerical wave tank to analyze its response in heave and pitch direction.

The results are amazing so far, but I know, that the center of mass (COM) has to be located a bit higher than currently (~0.5 m instead of 0.552 m below sea surface).
By varying this parameter, I observed a brief heave motion (floating up) of the pile. I really don't understand this, because the center of mass should neither influence the mass, nor the buoyancy (at least in equilibrium state).

First: heave_initial_COM.jpg

Then: heave_higher_COM.jpg

This effect intensifies by increasing the distance of the COM from the inital value.
I expected, that I could vary this parameter in height without any change in the initial equlibirum state (the pile is circular symmetric). It's just the center of mass and not the mass itself !
Does anyone have a clue what could be going on?

[CFD-Henning]

I just solved the problem.. lol
In fact I did not change the center of mass, but rather the center of rotation. OpenFOAM 1606+ printed, that the center of mass is set to the value of center of rotation. When I deleted the center of rotation parameter in the dynamicMeshDict, and just varied the center of mass parameter everything is fine:

heave_higher_COM_new.jpg

I still don't know, why a seperate definition of the COR differing from the COM induces an initial body movement.
To avoid an unintended body movement, I have to assume COM = COR. Nevertheless I would appreciate it, if s/o figures out how to set up a differing COR-value without influencing the initial equlibrium state in OF1606+.

Henning