Mass Properties

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

•	The principal moment of inertia

When you compute the solution, COMSOL adds the following variables:

Table 5-16: 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 — 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.