Added Mass
The Added Mass node is available on different geometrical entity levels, and can be used to supply inertia that is not part of the material itself. Such inertia does not need to be isotropic, in the sense that the inertial effects are not the same in all directions.
The Added Mass node is only available with some COMSOL products (see http://www.comsol.com/products/specifications/).
Layer Selection
This section is only present in the in the Layered Shell interface, where it is described in the documentation for the Added Mass and Added Mass, Interface nodes.
Coordinate System Selection
The added mass values are given with respect to the selected coordinate directions.
For more information about the special coordinate systems available in the Shell and Plate interfaces, see Added Mass in the documentation for these interfaces.
Face Defining the local Orientations
This section is only present in the Added Mass node in the Shell interface.
Added Mass
Select a Mass type using Table 4-10 as a guide. The default option is the type for the geometric entity. The added mass matrix can be entered as Isotropic, Diagonal, or Symmetric. For Isotropic the same mass is used in all the diagonal elements of the mass matrix.
Table 4-10: Available Mass Types based on geometric entity
Mass Type
variable
SI units
Geometric Entity Level
Mass per unit volume
pV
kg/m3
domains, boundaries
Mass per unit area
pA
kg/m2
domains, boundaries, edges
Mass per unit length
pL
kg/m
edges, points
Total mass
 m
kg
domains, boundaries, edges
Frame Acceleration Forces
Select the Exclude contribution check box to switch off the loads that can be caused by the added mass when the frame is accelerated when using a Gravity or Rotating Frame feature. The setting will also determine whether the node will contribute when computing mass properties; see Computing Mass Properties.
Location in User Interface
Context Menus
Solid Mechanics>Mass, Spring, and Damper>Added Mass (Domain, Boundary)
Solid Mechanics>Edges>Added Mass
Shell>Mass, Spring, and Damper>Added Mass (Boundary, Edge)
Plate>Mass, Spring, and Damper>Added Mass (Domain, Boundary)
Layered Shell>Mass, Spring, and Damper>Added Mass (Boundary, Edge)
Layered Shell>Points>Added Mass (Point)
Layered Shell>Mass, Spring, and Damper>Interfaces>Added Mass, Interface(Boundary, Edge)
Membrane>Mass, Spring, and Damper>Added Mass (Boundary, Edge)
Beam>Mass, Spring, and Damper>Added Mass (Edge)
Truss>Mass, Spring, and Damper>Added Mass (Edge)
Multibody Dynamics>Mass, Spring, and Damper>Added Mass (Domain)
Multibody Dynamics>Added Mass (Boundary)
Multibody Dynamics>Edges>Added Mass
Ribbon
Physics tab with Solid Mechanics selected:
Domains>Mass, Spring, and Damper>Added Mass
Boundaries>Mass, Spring, and Damper>Added Mass
Edges>Solid Mechanics>Added Mass
Physics tab with Shell or Membrane selected:
Boundaries>Mass, Spring, and Damper>Added Mass
Edges>Mass, Spring, and Damper>Added Mass
Physics tab with Plate selected:
Domains>Mass, Spring, and Damper>Added Mass
Boundaries>Mass, Spring, and Damper>Added Mass
Physics tab with Layered Shell selected:
Boundaries>Mass, Spring, and Damper>Added Mass
Boundaries>Interfaces>Added Mass, Interface
Edges>Mass, Spring, and Damper>Added Mass
Edges>Interfaces>Added Mass, Interface
Points>Layered Shell>Added Mass
Physics tab with Beam or Truss selected:
Edges>Mass, Spring, and Damper>Added Mass
Physics tab with Multibody Dynamics selected:
Domains>Mass, Spring, and Damper>Added Mass
Boundaries>Multibody Dynamics>Added Mass
Edges>Multibody Dynamics>Added Mass