Simulation coordinate systems

Coordinate systems help you perform both modeling and finite element operations. In Pre/Post, you can work with the following types of coordinate systems:

• Absolute coordinate system (also referred to as the global coordinate system)

• Work coordinate system (WCS)

• Local coordinate system

• Global cyclic analysis coordinate system

• Nodal reference coordinate system

• Nodal displacement coordinate system

Absolute coordinate system

The absolute coordinate system is automatically defined by the software and is permanent and not mobile. The absolute coordinate system is always Cartesian. It provides the frame of reference for all other coordinate systems, and it is used when exporting an input file for another solver. The software writes out the location of each node in the absolute coordinate system. The absolute coordinate system in Pre/Post corresponds to the Simcenter Nastran Basic coordinate system.

Work coordinate system (WCS)

Because the absolute coordinate system is not mobile, the work coordinate system (WCS) acts as a mobile coordinate system to facilitate geometry construction in different orientations. The WCS is the frame of reference for all modeling operations. You can locate and orient the WCS anywhere in model space.

You can create, orient, or examine an FE entity (or geometry) with respect to the WCS. However it is recommended to use the other types of coordinate systems, because the WCS is mobile, and it is difficult to keep track of the CSYS definition of the FE entities.

The WCS has a single and transient state. It does not have a cylindrical or spherical state, and you cannot use a WCS for a nodal reference coordinate system.

Local coordinate system

A local coordinate system is one you define. Local coordinate systems can help you with both part and finite element modeling operations. When you create a local coordinate system, you can a create Cartesian, cylindrical, or spherical coordinate system.

(1) Cartesian coordinate system; (2) Cylindrical coordinate system; (3) Spherical coordinate system

Global cyclic analysis coordinate system

A global cyclic analysis coordinate system is a cylindrical coordinate system whose Z-axis defines a default axis of rotation for your FEM. The global cyclic analysis coordinate system becomes the default coordinate system for certain boundary conditions and for the Assign Nodal Coordinate System command. You define the coordinate system in either the New FEM or the Edit FEM dialog box for the following cases:

• When your FEM does not include 2D solid elements for axisymmetric modeling, you define the cyclic coordinate system to specify the default axis of rotation for your model.

• When your FEM includes 2D solid elements for axisymmetric modeling, you specify a plane and axis of rotation, from which the software creates the cyclic coordinate system automatically.

The second case is available when the Enable Cylindrical Sys and Suppress Plane Check for 2D Solid Option early access feature is enabled. For more information, see Enable an early access feature.

Nodal coordinate systems

Each node in your model has a nodal reference coordinate system that determines the locations of the node coordinates (grid positions) that are written to the solver input deck, as well as a nodal displacement coordinate system that provides a frame of reference for the structural degrees of freedom with regard to both displacement and rotation.

By default, both of these nodal coordinate systems are the same as the absolute coordinate system. However, you can use the Assign Nodal Coordinate System command to change a node's reference or displacement coordinate system to a local coordinate system. For more information, see Working with nodal coordinate systems.

How do I

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Simulation coordinate systems, Simcenter 3D 2021.1 Series

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