Mass Properties
Introduction
You can add one or more Mass Properties nodes to create variables for and compute the following quantities for a model component:
•
The volume of the geometry or part of the geometry.
•
The mass of the geometry or part of the geometry
•
The center of mass
•
The moment of inertia, which is a quantity that determines the torque needed for a desired angular acceleration about a rotational axis.
•
The principal moment of inertia
When you compute the solution, the COMSOL Multiphysics software adds the following variables:
Table 5-15: Variables created by a Mass Properties Node
Quantity
Typical Variable names
Volume
mass1.volume
Mass
mass1.mass
Center of mass
mass1.CMX, mass1.CMY, mass1.CMZ
Moment of inertia
mass1.IXX, mass1.IXY, mass1.IXZ, and so on
Moment of inertia, principal direction
mass1.Ip1X, mass1.Ip2X, mass1.Ip3X, and so on
Moment of inertia, principal values
mass1.Ip1, mass1.Ip2, and mass1.Ip3
The namespace of the variables — mass1 in the table above — is unique for each Mass Properties node.
In general, the characters X, Y, and Z in the variable names in the table above are replaced by the coordinate names in the selected frame.
Use a Global Evaluation node, for example, to evaluate the resulting measurement quantities, which you can select from a Definitions>Mass Properties submenu after clicking the Replace Expression () or the Insert Expression () button.