Tips for Choosing a Solver in SOLIDWORKS Simulation

SOLIDWORKS Simulation has four options for solvers: Auto, FFEPlus, Direct Sparse, and Large Problem Direct Sparse. SimulationXpress uses FFEPlus solely.

If you are new to Simulation, always use Auto. SOLIDWORKS will pick the most efficient and most accurate solver for the particular study automatically.

The rest of this document will contain specifics on when the solvers will be less efficient and less accurate.

FFEPlus

FFEPlus is an iterative solver that uses implicit integration methods. Each iteration the solution is assumed and errors are evaluated. Iteration continues until errors are small enough. Thus, in general, if the study contains more than 100,000 DOF, it is more efficient and more accurate to use FFEPlus.

Will fail or be less accurate if there is:

• Incompatible mesh and any local bonded contact sets not automatically covered by global bonded contact
• Gravity or external forces in a frequency analysis
• Base excitation in a linear dynamic study
• A large difference in moduli of elasticity between parts
• Imported pressure or temperature results from other studies
• Circular/cyclic symmetry boundary conditions
• Nonlinear analysis

Less efficient than Direct Sparse if using:

• No Penetration contact, especially with friction effects
• Mixed meshing between beams and solids (if running SOLIDWORKS 2011 and below)
• Virtual wall boundary condition
• Pin and rigid connections
• Soft springs

Direct Sparse

Produces a direct solution using exact numerical techniques. “Sparse” refers to the sparsity (zeroes) in the matrices that it uses to find a solution. In general, it has a higher level of accuracy in small to medium sized problems. It is faster when more memory is available, however, memory requirements will increase faster than the size of the part increases. Use the Direct Sparse solver in small and medium-sized problems, if FFEPlus will produce less accurate results, and if doing a Nonlinear analysis.

Will fail or be less accurate if there is:

• Instability in the model
• Rigid body modes
• Millions of Degrees of Freedom (DOF)

Less efficient than FFEPlus if:

• Over 100,000 DOF in general analysis
• Over 50,000 DOF in Nonlinear studies
• Over 500,000 DOF in Thermal studies

Large Problem Direct Sparse

The LPDS Solver is the Direct Sparse solver with the ability to calculate using multiple cores. Thus, use the LPDS solver if the Direct Sparse solver is required and there is not enough RAM. It may sound like it should replace Direct Sparse, but that is not the case. Use LPDS only as a last resort.

Auto

The automatic option uses FFEPlus until certain conditions are seen in the study. SOLIDWORKS provides the following list for the current reasons Simulation switches from FFEPlus to Direct Sparse:

• Amount of RAM available before solver is launched
• If solver goes out of core before calculation completes
• Large displacement turned on
• Presence of Remote Loads
• Presence of Connectors
• Percentage of elements that are shells
• During convergence for No Penetration contacts
• Number of contact elements (generated during the solve) based on all contact definitions
• Bonded contact between mixed mesh elements (2011 and below)
• Circular symmetry
• In-plane loading
• Frequency shift option turned on

I hope you found this SOLIDWORKS Simulation guide helpful. For more Simulation tips and tricks check out the links below.

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