- Introduction
- COMSOL Multiphysics
- AC/DC Module
- Acoustics Module
- Batteries and Fuel Cells Module
- CAD Import Module and LiveLink™ Products for CAD
- CFD Module
- Chemical Reaction Engineering Module
- Corrosion Module
- ECAD Import Module
- Electrodeposition Module
- Fatigue Module
- Geomechanics Module
- Heat Transfer Module
- Material Library
- MEMS Module
- Microfluidics Module
- Nonlinear Structural Materials Module
- Optimization Module
- Particle Tracing Module
- Pipe Flow Module
- Plasma Module
- RF Module
- Structural Mechanics Module
- Subsurface Flow Module
- LiveLink™ for MATLAB®
- LiveLink™ for Excel®
- The COMSOL Java API

## New Products in Version 4.3a

The following new products are introduced with COMSOL Multiphysics version 4.3a:

- Fatigue Module extends the Structural Mechanics Module with functionality for fatigue analysis. See Fatigue Module for more information.

- LiveLink™ for Excel® gives you access to COMSOL model definitions and results data from an Excel spreadsheet. See LiveLink for Excel for more information.

- LiveLink™ for Solid Edge® provides a bidirectional interface to the Solid Edge CAD software. See CAD Import Module and LiveLink Products for CAD for more information.

- ECAD Import Module for importing ECAD geometries into COMSOL. See ECAD Import Module for more information.

## New Functionality in Version 4.3a

### General COMSOL Desktop Functionality

- A Cylinder selection feature makes it possible to create a cylinder for selecting objects in a geometry. This feature is similar to the Box and Ball selection features and can simplify selection of geometric entities in suitable geometries.

- You can select boundaries (faces) and edges in the geometry by continuous tangent in the Explicit, Ball, Box, and Cylinder selection features. That makes it possible to select, by just selecting a single face, for example, an entire sheet that consists of several faces (boundaries) that are connected so that their tangents are continuous (within an angular tolerance that you can specify).

- You can specify the browser to use for viewing COMSOL documentation in the Preferences dialog box. By default, COMSOL uses the system default browser, but you can also select to use a custom browser.

- The predefined physical constants in COMSOL now use the 2010 CODATA recommended values, which in some cases differ slightly from the previous values (from 2006). The COMSOL Multiphysics User’s Guide contains a list of all supported physical constants and their values, which now are the 2010 CODATA recommended values.

- The global variable
`numberofdofs`

reports the total number of degrees of freedom (DOFs) in the model, including any internal DOFs in the solver.

- It is now possible to plot the inverse function in addition to plotting the function itself for interpolation functions that you define.

- A warning is now issued if you use a reserved name for a built-in function (such as
`abs`

or`cos`

) as the name for a user-defined function. The name then turns orange, and a tooltip indicates that the chosen name is a reserved function name. Such warnings also appear for user-defined parameters and variables that use names that are reserved names for built-in variables such as`i, j, and pi.`

- New operators:

`integrate`

: Evaluates an integral of a general expression with respect to an integration variable over a real interval specified by lower and upper limits.

`circumcenter`

: Evaluates an expression in the circumcenter of the mesh element to which the point belongs.

`centroid`

: For simplex meshes, this operator evaluates an expression in the centroid of the mesh element to which the point belongs.

`env`

: Evaluates an expression at the coordinates of a particle in a domain. Requires the Particle Tracing Module.

`bndenv`

: Evaluates an expression at the coordinates of a particle at a boundary. Requires the Particle Tracing Module.

## Geometry and Mesh

### New Geometry Tools and Functionality

- Global x-, y-, and z-axis as predefined options for axis direction in 3D geometry features such as 3D geometry primitives (Block, for example) and applicable geometry operations (Rotate, for example) and selection types (Cylinder, for example) are now available from the Axis type lists in addition to general Cartesian and spherical axes.

- The Interpolation Curve feature can now read curve coordinates from file on the sectionwise data format in addition to the spreadsheet data format. You can also specify the curves as vectors of x-, y-, and z coordinates.

- The behavior when moving geometry objects directly in the Graphics window has been improved so that a move updates the position of the original geometry object instead of creating an explicit Move feature.

### New Meshing Tools and Functionality

- Ball and Box wireframe visualization in mesh import sequences for partitioning of imported meshes by splitting geometric entities by creating at least one new geometric entity for the elements enclosed in the specified ball or box.

- Logical Expression feature for mesh import so that the imported mesh can be partitioned into separate domains, for example, by creating at least one new geometric entity for the mesh elements that fulfill the specified logical expression.

- Automatic refinement of the starting mesh at sharp corners.

- Support for boundary layers on isolated boundaries.

## Physics Interfaces

- Improved constraint settings for Dirichlet-type boundary conditions. If you activate the Advanced Physics Options, boundary conditions such as Dirichlet Boundary Condition or a Temperature condition includes a Constraint Settings section with new options. From the Apply reaction terms on list:

- Select All physics (symmetric) to apply reaction terms bidirectionally on u as well as on any other dependent variables appearing in r. This corresponds to the bidirectional (symmetric) constraint in version 4.3.

- Select Current physics (internally symmetric) to apply reaction terms on all components of u. This is a new constraint type.

- Select Individual dependent variables to apply reaction terms from each active component in the Dirichlet condition only on the corresponding component of u. This is the default setting and corresponds to the unidirectional constraint in version 4.3.

- New Wave Form PDE interfaces, mathematical interfaces that are based on the discontinuous Galerkin method for use with the time-explicit solver.

- Predefined flux variables for accurate evaluation of boundary fluxes are now
available for the Coefficient Form PDE and General Form PDE user interfaces,
where it is enabled by default. The flux variables are also available in the structural
mechanics user interfaces but there you need to activate them first. For example,
`dflux.u`

is the boundary flux in the down direction for a dependent variable u in a Coefficient Form PDE. To create variables for boundary fluxes, select the Compute boundary fluxes check box in the physics interfaces Discretization section.

## Studies and Solvers

- Get Initial Value is available as an option on the Study level and for each study step node. Using this option makes COMSOL evaluate the solution and variables using the initial values, which makes it possible to plot and evaluate the solution and any solution-dependent variables using the initial values as the solution.

- Compute commands are now available for individual study steps (without opening the solver sequence): When applicable, each study step includes options to Compute to Selected, Compute Selected Step, and Compute from Selected for easier testing and debugging of large models with several study steps.

- Support for running COMSOL on the Amazon Elastic Compute Cloud™ (Amazon EC2™). This is made possible by the addition of new remote access tools for optimized data transfer, which you can run from the COMSOL Desktop or in batch mode. See the separate Running COMSOL on the Amazon Cloud document for details.

- Improvements to solution selection in the Study and Dependent Variables nodes:

- The possibility to select a solution number manually. This input can be used for parametric sweeping with time-dependent and eigenvalue and parametric solutions as input.

- The options First and Last are available as options for the solution numbers to select.

- Specification of Initial values of variables solved for is now available also on the study step level and not only in the solver sequence.

- Export of system matrices (stiffness matrices, mass matrices, and so on) from the Modal Solver, which can now provide mode-reduced system matrices, and from the Assemble feature. Under Derived Values in the Results branch, you can add a System Matrix node where you specify which of the computed system matrices to output and if you want to output them using a sparse of full format.

- Input of system matrices generated outside of COMSOL using an Input Matrix subnode to a solver node, where you can specify which system matrices and vectors that should use external data in Java. The saved Model Java-file contains code for inputting the selected matrices and vectors.

- Pseudo time stepping is now available for the stationary solver when using a fully coupled or segregated solver. Pseudo time stepping is used in transport problem to stabilize the convergence toward steady state. Here an adaptive feedback regulator controls a CFL (Courant–Friedrichs–Lewy) number which is then used for pseudo time stepping. In the CFD Module, solver defaults control the pseudo time stepping for stationary fluid-flow models.

- Improved parallel performance for shared-memory/multicore computers and for distributed computing:

- Multicore computing: Greatly improved handling of constraint boundary conditions such as fixed temperature, electric potential, and displacement speeds up computations for most physics. Performance increase is thanks to new constraint elimination algorithms

- Distributed computing: Solvers have been optimized by the introduction of a very efficient sparse matrix reordering algorithm for direct solvers, and communication for matrix-vector data has been optimized.

- Domain point probes and boundary point probes can now follow a certain frame type (spatial, material, geometry, or mesh) in a model with multiple frames.

### Results

- Transparent background for image snapshots using PNG format, making it easier to integrate COMSOL images into documents and combining them with other graphics.

- The Join data set now supports the norm of difference as a method for joining two solutions, so that you can evaluate and plot that quantity when comparing solutions.

- Improved placing and display of labels on logarithmic x- and y-axes.

- More flexible legend positioning: Middle left and Middle right have been added as additional legend positions.

- Options to invert the phase (change the sign) when rotating and reflecting are now available as options in Sector 2D and Sector 3D data sets for more flexibility when rotating and reflecting results data.

- In the Filter subnode for the Particle Trajectories plot (for the Particle Tracing Module), it is now possible to specify a logical expression for the particle to include.

- Improved settings for animation, with better support for animating parametric solutions and added possibility to specify the number of frames in the generated movie.

## Backward Compatibility vs. Version 4.3

### New terminology for constraint types

The following constraint types in version 4.3 have new names in version 4.3a:

- Bidirectional, symmetric is now Apply reaction terms on: All physics (symmetric).

- Unidirectional is now Apply reaction terms on: Individual dependent variables.

### Weak constraints updates for the laminar flow interface

The weak constraints formulation for the following boundary conditions has been updated:

- Symmetry

- The Slip option in the Wall feature

These boundary condition are now formulated using the same set of Lagrange
multipliers as all the other boundary conditions in the Laminar Flow interface. The
previously used Lagrange multiplier `un_lm`

has been removed.

Models saved in version 4.3 can be opened and postprocessing will include un_lm until
the model is re-solved. In some cases, occurrences of `un_lm`

in the solver sequence
must be replaced manually. This is the case if `un_lm`

was the only Lagrange multiplier
component in a segregated group or the only Lagrange multiplier component of a
Vanka smoother. Alternatively, generate a new automatic solver sequence. Models
saved in versions previous to version 4.3 must either be re-solved in version 4.3a to be
possible to postprocess, or opened and re-saved in version 4.3 before opened in version
4.3a.

### Automatically created identity/contact pairs

Face normals and edge directions may change for geometries with CAD representation. This may happen if you rebuild the geometry sequence for a model that you created in an earlier COMSOL version. Face normals and edge directions are now consistent between CAD and COMSOL representations.