Moment computation on floatings

AlanCattelliot

Dear All,

I am testing hydrostatics calculations using your code. Having created a floating body, I prescribe its mass and limit the degree of freedom to translation in Z and rotation in Y :

<floatings>

           <floating mkbound="20">

      <massbody value="1830" />

               <center x="-0.492" y="-0.24050272606869844" z="-1.363958737921908" />

      <translationDOF x="0" y="0" z="1" />

      <rotationDOF x="0" y="1" z="0" />

           </floating>

I then compute the movement of the floating body and the moment along the X axis using :

%floatinginfo% -dirin %diroutdata% -savedata TP70_mvt

%computeforces% -dirin %diroutdata% -momentaxis:0:0:0:1:0:0 -onlymk:31 -viscoauto: -savecsv TP70_force

Here is the results of the results that I have for different rotation angles of my floating body.

(Convergence as a function of simulation time in seconde / The angle of rotation is to be seen in the legend)

Convergence has been checked for longer time of simulation and is estimated ok for the purpose.

(Buyoancy check as a function of the angle of rotation in degree / (ForceFluidy']**2 + 'ForceFluidz'**2)**(.5), ForceFluidy, ForceFluidz as given in TP70_force )

Buyoancy if OK taking account into the precision of the model

(Righting moment as a function of the angle of rotation in degree ? / 'Momentm' as given in the computed output TP70_force )

I expect the computed moment to become negative at a point. But it does not happen.

(floating object @ convergence / From left to right, each model correspond respectively to the angle of rotation 10°,63°,117°,170°. Water level is symbolized by the grid @z=0 in Blender)

Between the two first cases and the two last cases, the buyoancy swaps from side to side, so the sign of the Y coordinates of the buyoancy center changes. Should'nt the computed moment along the X axis do the same ?

Thanks for your attention and your kind help.

AlanCattelliot

Dear all,

I should probably have labelled my post with the word "error in moment calculation on floatings".

In the hope that someone could have an hint on why the moment of forces computed does not change sign with the Yposition of the buyoant volume in my case.

Thanks in advance