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/).
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.
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.
