Learning Forum

[NavalArch]

Good day,

I want to define moment of inertia as point mass input for a rectangular body in AQWA. I was wondering by saying moment of inertia, whether it is 2nd moment of inertia or mass moment of inertia since it is in kg.m2 and the documentations are not clear enough to me.

I would appreciate if you could provide me a document or more information regarding this matter.

Best regards,

[NavalArch]

I am also wondering wethear the definition of Moment of Inertia is about perpendicular axis or central axis.

[mjmiddle]

2nd moment of interia is an area moment used on only geomerty (no volume or mass). It is for reduced geometry: cross section of beams and shells. The moment of inertia specified on point mass (MASS21) is a mass moment of intertia with MKS units of kg.m^2. There are real constants Ixx, Iyy, Izz for 3D analysis. These moments are about the element coordinate system axes. The element coordinate system wil be aligned with the global coordinate system if you did not specifically set the orientation. See the help page for MASS21:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/ans_elem/Hlp_E_MASS21.html

The mass moments of intertia are specified with real constants 4-6. KEYOPT (3) must be zero to use the mass moments of interia. for 2D analysis, there are slight differences. See the help.