Gravity
When you add a Gravity node, gravity forces are applied to all selected features in the physics interface with a density, mass, or mass distribution. You select objects having the highest geometrical dimension of the interface, and all objects with a lower dimensionality which belong to the selection are automatically included.
The gravity acts in a fixed spatial direction. The load intensity is g = ρgeg where g as a default is the acceleration of gravity (a predefined physical constant). The action of gravity can also be seen as a linearly accelerated frame of reference.
The Gravity 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 Gravity node.
Coordinate System Selection
The Global coordinate system is selected by default. The Coordinate system list contains any additional coordinate systems that the model includes. It can be used when prescribing the direction of the gravitational forces.
Gravity
Enter the components of the Gravity g. The default value is g_const, which is the physical constant having the value 9.8066 m/s2.
For 2D components, the default is that the gravity acts in the negative y direction. For 3D and 2D axisymmetric components, the default is that the gravity acts in the negative z direction.
Only features which have a geometrical selection contribute to the mass forces. The Mass and Moment of Inertia nodes are global features and will not get any contribution from Gravity.
Location in User Interface
Context Menus
Solid Mechanics>Volume Forces>Gravity
Shell>Face and Volume Loads>Gravity
Layered Shell>Face and Volume Loads>Gravity
Plate>Face and Volume Loads>Gravity
Membrane>Face and Volume Loads>Gravity
Beam>Line and Volume Loads>Gravity
Truss>Line and Volume Loads>Gravity
Multibody Dynamics>Volume Forces>Gravity
Ribbon
Physics tab with Solid Mechanics or Multibody Dynamics selected:
Domains>Volume Forces>Gravity
Physics tab with Shell, Layered Shell, or Membrane selected:
Boundaries>Face and Volume Loads>Gravity
Physics tab with Plate selected:
Domains>Face and Volume Loads>Gravity
Physics tab with Beam or Truss selected:
Edges>Line and Volume Loads>Gravity