COMSOL Multiphysics

New Products in Version 4.2a

The following new products are introduced with COMSOL Multiphysics version 4.2:

• Particle Tracing Module: A new module for simulation of particle trajectories with specialized interfaces and plot types for particle tracing of charged particles in electric fields, mass particles in fluid flow, optical rays, and more. See Particle Tracing Module for more information.

• LiveLink for Creo™ Parametric: A new LiveLink for connecting COMSOL Multiphysics it to the 3D CAD software Creo Parametric from PTC.

New Functionality in Version 4.2a

General COMSOL Desktop Functionality

• The Previous Node and Next Node buttons provide quick navigation between modeling steps in the Model Builder.

• You can now select multiple nodes in the model tree to, for example, quickly delete entire chunks of model definitions.

• A new Image function makes it possible to import images on PNG, BMP, GIF, and JPEG formats. You can use the image data for material distribution or to identify regions with different materials by their color or grayscale.

• A new Elevation (DEM) function for importing elevation data in the DEM format, which was created by the US Geological Survey. A DEM file contains elevation data for a portion of the Earth’s surface. This can be used to define a function z = f (x, y). The resulting function behaves essentially like a grid-based interpolation function. You can then combine these DEM surfaces with solids to form a volumetric representation of geometry and mesh.

• Improved Model Library search function: The search now uses all words in the Search field, but they do not need to appear together in a phrase. To search for an exact wording or phrase, enclose it in quotes.

• New material container variable root.material simplifies access to material data. For example, root.material.rho is the density ρ as defined by the materials in each domain in the geometry. For plotting, you can type the expression material.rho to create a plot that shows the density of all materials.

• New additional time-dependent solutions operators that you can use for results evaluation, for example:

• timeint() for time integration

• timeavg() for time averages

• New additional prestressed and small-signal analysis operators:

• lintotalavg() evaluates the average of an expression over all phases for a linearized solution

• lintotalrms() evaluates the RMS (root mean square) of an expression over all phases for a linearized solution

• lintotalpeak() evaluates the maximum of an expression over all phases for a linearized solution

Geometry and Mesh

• It is now possible to interactively sketch 2D primitives on work planes directly in the 3D geometry. Activate by selecting the Draw on work plane in 3D check box. This setting is also available as a preference entry. Two new toolbar buttons provide Work Plane Clipping and Align with Work Plane functionality for simplifying geometry creation using work planes.

• The new Interpolation Curve feature in 2D and 3D creates interpolation curves based on look-up table data (entered as x, y, and z values in a table or imported from file). The feature constructs a cubic spline that interpolates or approximates the given points.

• You can now include a geometry sequence from another model file. If the geometry sequence contains references to functions or parameters, those functions and parameters are also inserted into the model.

• Cut-and-paste geometry objects and operations in the Model Builder tree.

• Interactively stretch and shape 2D objects in the Graphics window.

• N-to-M mesh sweeping: That is, a swept mesh over a domain with N faces on the source side and M faces on the destination side. In general, it is required that the partitioning of the source (into faces) is a refinement of the partitioning on the destination. In particular, it is always true that N ≥ M.

• The new copy mesh (Copy Domain, Copy Face, and Copy Edge in 3D; Copy Domain and Copy Edge in 2D) functionality makes it possible to copy the mesh from a meshed entity to an unmeshed entity. The transformation (for the mesh) must be a rigid body transformation, but a constant isotropic scaling and mirroring is allowed (that is, it is possible to copy from a large circle to a small but not from a circle to an ellipse). If, for example, a boundary of the destination domain is already meshed, the mesh of the source must match at the corresponding boundary. The feature supports N-to-1 copy, meaning two adjacent half-spheres will copy to a complete sphere. The destination can be multiple; that is, the destination can be several spheres, each getting identical meshes. N-to-N copy, meaning an array of cubes can be copied to a similar array of cubes.

Physics Interfaces

• The PDE interfaces for equation-based models now support units. By declaring quantities for the dependent variables and the source terms (the overall equation), the PDE interfaces defines and displays units for all equation terms and quantities. This makes it possible to mix equation-based modeling with other physics interfaces and at the same time make full use of the unit system in the model (the PDE interface then introduces no unexpected or undefined units). You can switch off the unit handling for working with dimensionless quantities.

• Clear indication of the default nodes for all physics interfaces. In the Model Tree, a D in the upper-left corner indicates that the node is a default node.

Studies and Solvers

• Improved user interface for parametric sweeps:

• Accumulated probe tables for numerical results from nested parametric sweeps

• Response surface plots

• New interface for “off-line” sweeps

• Improved multiple-parameter sweeps

• Improved performance for time-dependent problems using new scaling.

• More robust automatic remeshing for time-dependent problems

• Possibility to avoid “complex pollution” (small nonzero imaginary components) by splitting complex variables into real and imaginary parts. You can declare field variables as complex or real when using the splitting of complex variables.

• Improvement to the least-squares solver:

• Parameters and coordinates can be stored in files.

• A symbolic gradient is available for stationary problems.

Results

• A new Join data set provides the possibility to do superposition and comparison of solutions from two different data sets. You can form combinations of solutions using difference, sum, product, quotient, and more general and explicit expressions. For example, using the Join data set you can plot and evaluate the difference between two solutions in a mesh convergence study.

• A new Accumulated Probe Table feature enables a probe to write multiparameter data to tables. For example, the table can include the results from a nested parametric sweep with two independent parameters. From the table you can create a new Table Surface plot for plotting response surfaces, for example, and a new Table Graph for a graph plot of the results versus a parameter, for example.

• Interactive slice and isosurface plots , where you can move the slices and isosurfaces interactively in the Graphics window using a slider, provides easy positioning of the slices and isosurfaces.

• Multislice plots for easy generation of multiple slices in different directions.

• Import of external data to tables. The data can be spreadsheet data or other external data in common text-file formats. Importing external can be useful for analyzing and plotting experimental data, for example.

• For all Max/Min markers you can now select the color of the marker text in the Coloring and Scale section, including a custom color. This makes it possible to show a color that is more visible against the background than the default black color.

• Custom plot titles: The Title section for plots now provides a Custom setting for creating a customized plot title. When you select Custom you get a number of options for the typical components of a plot title: the data set (and its phase and solution when applicable) and the type, description, expression, and unit for the plotted quantity. You can also add a user-defined prefix and suffix.

Backward Compatibility vs. Version 4.2

New Scaling of Absolute Tolerances

A new technique to automatically compute the scaled absolute tolerance has been added. This mechanism computes the error weights in a new way for the BDF solver (for time dependent problems) for fields using the automatic scaling method. The new method is enabled by default but you can turn it off in the Time Stepping (clear the Update scaled absolute tolerance check box). Opening an old model the new mechanism will be turned off automatically. But when regenerating a new solver, it will be enabled. Note that when running a model using the API, the new mechanism will be used. If you want the old behavior you can set the property ewtrescale to off for the time-dependent solver you are using.

As an effect of this new mechanism the default relative and (global) absolute tolerance for models involving Reaction Engineering Physics interfaces has been changed to 1e-3 and 1e-4, respectively. This change will also apply to newly generated solvers, but not when reading and old Model MPH-files. For a model using the API that does not set these tolerances explicitly, the new defaults will apply.

New Geometry Frame

The frame where the geometry keeps its original shape, as defined by the geometry sequence, is now called the geometry frame. The Deformed Geometry interface defines the material frame based on the geometry frame, which in turn differs from the mesh frame when using manual or automatic remeshing.

Backward Compatibility vs. Version 3.5a

Deformed Geometry Interface

The Parameterized Geometry application mode in versions 3.5a, which is limited to 2D, is replaced with the Deformed Geometry interface in version 4.2a. This interface is available in 2D and 3D. The Deformed Geometry interface deforms the mesh using an arbitrary Lagrangian-Eulerian (ALE) method and is not the parameterized geometry using geometric parameter sweeps (see above).

In the version 4.2a interface, the Linear Displacement and Similarity Transform boundary conditions are not yet available as preset conditions. Those boundary conditions are planned for version 4.3.

In version 4.2a, you can create the corresponding conditions by manually entering variables.

Backward Compatibility for pre-3.5a models

COMSOL 4.2a can load models saved from version 3.5a. For loading models from earlier COMSOL versions than 3.5a you need to load them in COMSOL 3.5a and then save them. For simplifying this task a utility is available where you can convert all files in a directory from versions 3.0–3.5 to version 3.5a. See the section COMSOL Convertpre35a Command for Windows, the section COMSOL Convertpre35a Command for Linux, or the section COMSOL Convertpre35a Command for the Mac in the COMSOL Installation and Operations Guide for more information.