Monday, November 2, 2015

Nodal Bandwith : FEA Understanding, Reducing Nodal Bandwidth

Reducing Nodal Bandwidth

If you're using an external solver, you can use the Node, Bandwidth Manage menu commands to reduce the nodal bandwidth or profile in your model.

Understanding Nodal Bandwidth

Nodal bandwidth measures whether the node numbering in a finite element model will allow the solver to reach a solution in a reasonable amount of time. To perform a linear statics analysis, the finite element solver assembles a stiffness matrix. The amount of time required to solve the model is directly related to the size of the stiffness matrix.

Bandwidth and profile are two related but different means of matrix conditioning.

  • The model's half-bandwidth is the width of one row of the stiffness matrix, measured from the first column to the diagonal.
  • The profile is the total number of all the potentially non-zero terms in the stiffness matrix, above and including the diagonal.

Reducing Bandwidth by Sweeping Along Axes:

You can also reduce nodal bandwidth by sweeping along the axes (Sweep Coordinate Axes).

  • Select the elements.
  • Specify the coordinate system for the sort operation to reference.
  • Select the axis sequence (which axis to sort first, second, last).

The software sorts along each axis of the coordinate system, one axis at a time. Beginning with the first axis, the software finds the node closest to the origin and puts it first in the list. If two or more nodes have the same coordinates, the software sorts along the second axis. If two or more nodes have the same coordinates along the second axis, the software sorts along the third axis.

After it finds the closest node, the software finds the next closest node and puts this node second in the list. This sort operation continues until the software sorts all nodes that you selected. The result is a re-sequenced node list, which you can use to relabel nodes in the model. In this example, the software sorts the X, Y, and then the Z axes.