Electrostatic Current and Voltage

Multipliers

There are two multipliers that control the magnitudes of various electrostatic loads when they are applied to the model. These are located in the Analysis Parameters dialog box on the General tab. The value Boundary voltage multiplier multiplies the magnitudes of any applied voltages on the model. The value in Current or charge sources multiplier multiplies the magnitudes for any charge or current loads on the model.

A value of zero in any of these fields except for Boundary voltage multiplier disables the loads of that type in the model. A value of 0 in Boundary voltage multiplier changes the magnitudes of the applied voltages to 0.

Calculate Flow Lines for 2D Models

For 2D models, if the Invoke flow-line generator check box in the Options tab of the Analysis Parameters dialog is activated, the contours of the flow of the current through the model are calculated. These contours are viewable in the Results environment.

Solver Options Section

The type of solver for an electrostatic analysis can be selected in the Analysis Parameters dialog box, Solution tab, in Type of solver. See also Types of Solvers Available for background information. The options available are as follows:

Automatic When selected, the processor chooses between the Iterative (AMG) and Sparse options based on the model size. The sparse solver is the optimum solver for mid-sized models. The iterative solver is the optimum solver for large models and requires less RAM. If a 64 bit processor is available on the system, the iterative and BCSLIB-EXT solver takes advantage of it.
Sparse Uses one of two available sparse solvers available in the Type of sparse solver drop-down box. The sparse solvers use multiple threads/cores when available.
Iterative (AMG) Uses an iterative scheme to solve the system of equations. The iterative solver uses multiple threads/cores when available.

If you want to create the solution matrix, but not perform the analysis, activate the check box for Stop after stiffness calculations. The only time it is useful is if you must access the equation number matrix. Otherwise, the stiffness matrix is always calculated when running an analysis, so there is no advantage to use this option in normal circumstances.

For the sparse and iterative solvers, the Percent memory allocation field controls how much of the available RAM is used to read the element data and to assemble the matrices. A small value is recommended. (When the value is less than or equal to 100%, the available physical memory is used. When the value of this input is greater than 100%, the memory allocation uses available physical and virtual memory.)

As listed above, some of the solvers take advantage of multiple threads/cores available on the computer. The drop-down Number of threads/cores control is enabled in such situations. You want to use all the threads/cores available for the fastest solution, but might choose to use fewer threads/cores if you need some computing power to run other applications at the same time as the analysis.

Iterative Solver Section

If the iterative solver is chosen, then the Iterative Solver section is enabled. The input for this section is as follows:

The Convergence tolerance field determines how accurate a solution is found to the matrix of equations. The smaller the tolerance, the more accurate the solution.
Maximum number of iterations stops the analysis if the matrix of equations is not solved within this number of iterations.
Attention: The accuracy of the solution depends on the convergence tolerance. A smaller tolerance results in a more accurate solution but may take more iterations. As with any iterative solution, check the results to confirm that they meet the appropriate accuracy. In some cases, performing the analysis twice with a different convergence tolerance is the best way to confirm the accuracy.

Sparse Solver Section

When chosen, the Sparse Solver section is enabled. The input is:

Type of sparse solver contains a list of sparse solvers currently available. (The sparse solvers are available only for the Windows operating system.) The sparse solvers available are as follows:
- Default use BCSLIB-EXT solver.
- BCSLIB-EXT use the Boeing solver. The BCSLIB-EXT solver can write temporary files to the folder specified by the environment variable USERPROFILE. By default, this variable is set to the folder C:\Documents and Settings\Username where C: is the drive on which the operating system is installed. The error numbers -701 or -804 returned from the BCSLIB-EXT solver means that it ran out of hard disk space for storing the temporary files. If this occurs, change the USERPROFILE variable to a directory that can provide sufficient hard disk space. (See the Windows Help and Support for documentation on changing environment variables.)
Solver memory allocation sets the amount of memory to use during the sparse matrix solution for the BCSLIB-EXT solver. Allocating more memory results in a faster analysis. The other sparse solvers adjust the memory setting automatically, so no setting is required for them.

Control Data in Text Output Files

After the analysis is complete, the analysis results can be output to a text file. Use the Analysis Parameters dialog box, Output tab, to control the data that is output to this file.

Contact Options

There are two methods of handling bonded connections. The method used depends in part on whether the nodes are matched between the two parts or not matched.

Activating the option Enable smart bonded/welded contact uses multi-point constraint equations (MPCs) when necessary to bond the nodes on part A, surface B with the nearest nodes on part C, surface D. Shape functions interpolate the potential at the nodes on surface B to the nodes on surface D. Therefore, the meshes do not need to match between the parts. The MPCs are used for all the nodes on the surface contact pair whenever any node does not match. If the meshes do match at all nodes, then node matching is used to bond the contact surface. The two vertices on the adjoining parts are collapsed to one node, and MPC equations are not used for the contacting surfaces. The options for the smart bonding drop-down are as follows:

None Smart bonding will not be used. Therefore, the nodes must match in order for parts to be bonded.
Coarse bonded to fine mesh Smart bonding creates MPC equations that connect the nodes on the surface with the coarser mesh to the nodes on the surface with the finer mesh.
Fine bonded to coarse mesh Smart bonding will create MPC equations that connect the nodes on the surface with the finer mesh to the nodes on the surface with the coarser mesh.

The smart bonding option applies to bonded contact and welded contact. Other types of contact (except for Free) require the nodes to be matched. See the page Meshing Overview: Creating Contact Pairs: Types of Contact for a discussion of defining contact and using smart bonding.

By default, smart bonding uses the condensation method to solve your analysis. If you find your analysis doesn't converge or is not performing as you expect, you can try a different Solution method to use with MPC equations (see Multi-Point Constraints). Click SetupLoadsMulti-Point Constraint and choose from the Solution method options. If you use the Penalty Method, the accuracy of the solution is controlled by the Penalty multiplier field. The Penalty multiplier, times the maximum diagonal stiffness in the model, is used during the penalty solution. A value in the range of 10² to 10⁴ is recommended.

Note: The solution method you select in the Define Multi-Point Constraints dialog box becomes the method used for all features that include MPCs. These features include, but are not limited to, cyclic symmetry, frictionless constraints, smart bonding, and user-defined MPCs. For example, if you want to use the Penalty Method to solve all your analyses involving smart bonding, you can override the default condensation method by selecting Penalty Method in the Define Multi-Point Constraints dialog box.

When the option Enable smart bonded/welded contact is not activated, the parts are bonded only if the nodes match between the parts.