Gravity
When you add a Gravity node, gravity forces are applied to features in the physics interface with a density, mass, or mass distribution.
The fluid in the pipe is included in the direction transverse to the pipe, but not in the axial direction. To include the gravity load in the axial direction caused by mass of the fluid, you will typically have to add extra point loads at discontinuities like pipe bends.
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).
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 Global coordinate system is selected by default.
Gravity
Enter the components for Gravity g. The default value is g_const, which is the gravitational acceleration constant at mean sea level having the value 9.80665 m/s2.
For 2D components, the default is that the gravity acts in the negative y direction. For 3D components, the default is that the gravity acts in the negative z direction.
Only features that 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. You may need to add extra force contributions if such nodes are present.
Frame Acceleration Forces
In versions earlier than 6.1, the Gravity node was a feature with domain selection. In a model created in an earlier version, the old Gravity 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 Gravity is appropriate.
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If the current Gravity 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 Gravity 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
Pipe Mechanics>Gravity
Ribbon
Physics tab with Pipe Mechanics selected:
Global>Gravity