Base Excitation
The Base Excitation node is used to represent an acceleration that is applied at all constraints. The main use case is for modal based analyses, in which case it is not possible to directly prescribe nonzero displacements at constrained degrees of freedom. It is however possible to use Base Excitation in any type of dynamic analysis.
The fluid in the pipe is included in the direction transverse to the pipe, but not in the axial direction. To include the inertial 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.
When a structure is subjected to a base excitation, displacements, velocities, and accelerations are measured relative to a space fixed coordinate system.
Coordinate System Selection
Select a coordinate system in which the base acceleration vector is represented. Only systems with space-independent axis directions are consistent with the assumptions of the base excitation.
Base Excitation
Enter the Base acceleration, ab.
A degree of freedom should either be constrained or free in the direction where the base excitation acts. Having a constraint acting in a local direction that is not either aligned or orthogonal to the excitation may produce unexpected results.
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 Base Excitation. You may need to add extra force contributions if such nodes are present.
Location in User Interface
Context Menus
Pipe Mechanics>Base Excitation
Ribbon
Physics tab with Pipe Mechanics selected:
Global>Base Excitation