Gravity

When you add a node, gravity forces are applied to all features in the physics interface with a density, mass, or mass distribution.

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 node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).


	Gravity is not available in 1D axisymmetry.

Coordinate System Selection

Select a coordinate system in which the gravity field vector is represented. Only systems with space-independent axis directions are consistent with the assumptions of this feature. The is selected by default.

Gravity

Enter the components for g. The default value is g_const, which is the gravitational acceleration constant at mean sea level having the value 9.80665 m/s2.

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For 3D, the default is that the gravity acts in the negative z direction.

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For 2D, the default is that the gravity acts in the negative y direction.

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For 1D, the default is that the gravity acts in the negative x direction.

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For 2D axisymmetry, the default is that the gravity acts in the negative z direction.


	Frame Acceleration Forces

In versions earlier than 6.1, the node was a feature with domain selection. In a model created in an earlier version, the old node remains unchanged. For such a model, it is recommended to use the newer functionality. There are different options:

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In most cases, switching to the new version of is appropriate.

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If the current node has a selection, which is not the entire model, or if it contains expressions that depends on the spatial coordinates, you can replace it by a Linearly Accelerated Frame node.

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If the current node is used to represent an acceleration imposed by the foundation, consider replacing it by a Base Excitation node.

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You can add a Harmonic Perturbation subnode for specifying a harmonic variation of the values of the prescribed displacements and rotations in a frequency domain analysis of perturbation type.

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You can assign this load to a load group. See Load Cases in the Structural Mechanics Modeling chapter.

Location in User Interface

Context Menus

Ribbon

Physics tab with a structural mechanics interface selected: