Selecting a Solver in ANSYS
In the solution phase of an analysis, the computer takes over and solves the simultaneous equations that the finite element method generates. The results of the solution are:
- Nodal degree-of-freedom values, which form the primary solution
- Derived values, which form the element solution
The element solution is usually calculated
at the element’s integration points. The ANSYS program writes the results
to the database as well as to the results file (.RST, .RTH, .RMG, or .RFL
files).
Several methods of solving the simultaneous equations are available
in the ANSYS program: frontal solution, sparse direct solution, Jacobi
Conjugate Gradient (JCG) solution, Incomplete Cholesky Conjugate Gradient
(ICCG) solution, Preconditioned Conjugate Gradient (PCG) solution, and an
automatic iterative solver option (ITER). The frontal solver is the default,
but you can select a different solver using one of the following:
Command: EQSLV
GUI: MainMenu>Preprocessor>Loads>Analysis Options
Main Menu>Solution>Sol’n Control:Sol’n Options Tab
Main Menu>Solution>Analysis Options
Main Menu>Solution>Unabridged Menu>Analysis Options
(Final Menu Path is valid beginning with ANSYS Revision 5.6)
Solver Selection Guidelines (general guidelines you may find useful in selecting which solver to use for a given problem.)
| Solver | Typical Applications | Model Size | Memory Use | Disk Use |
| Frontal Solver (direct elimination solver) | Use when robustness is required (nonlinear analysis) or when memory is limited. | Under 50,000 DOF | Low | High |
| Sparse Direct Solver (direct elimination solver) | Use when robustness and solution speed are required (nonlinear analysis), or for linear analysis where iterative solvers are slow to converge (especially for ill-conditioned matrices, such as poorly shaped elements). | 10,000 - 500,000 DOF (more for shell and beam models | Medium | High |
| PCG Solver (iterative solver) | Use when solution speed is crucial (linear analysis of large models). Especially well suited for large models with solid elements. | 50,000 - 1,000,000+ DOF | High | Low |
| ICCG Solver (iterative solver) | Use when solution speed is crucial in multiphysics applications. Handles models that are harder to converge in other iterative solvers (nearly indefinite matrices). | 50,000 - 1,000,000+ DOF | High | Low |
| JCG Solver (iterative solver) | Use when solution speed is crucial in "single-field" problems (thermal, magnetics, acoustics, and multiphysics). | 50,000-1,000,000+ DOF | Medium | Low |
For a more complete description of solvers, refer to the Basic
Analysis Guide found in the ANSYS online documentation.
