*Released March 9, 2011.*

This update corrects several bugs and stability issues in COMSOL 4.1. The update is cumulative; that is, it applies to both COMSOL 4.1 and the previous COMSOL 4.1 Update 1 and Update 2. The update includes all updates from the previous Update 1 and Update 2. Update Details.

## Installation

### Check your version

Make sure that you run COMSOL version 4.1.0.88, 4.1.0.112 or later. On the **Help** menu,
click **About COMSOL Multiphysics** to check your version. If you have an
earlier build number, contact your COMSOL sales representative to get
the official release of COMSOL 4.1 before you proceed.

### Download Update

Windows | comsol_4.1.0.185_win.exe | 54.0 MB | |

Linux | comsol_4.1.0.185_linux.zip | 67.9 MB | |

Mac OS X | comsol_4.1.0.185_mac.dmg | 53.3 MB |

### Install

Before you proceed with the installation, make sure to exit any running COMSOL process.

#### Windows

Run the downloaded .exe-file to extract the update to the COMSOL 4.1 installation directory, for
example `C:\COMSOL41`

.

#### Linux

Copy the downloaded .zip-file to the COMSOL 4.1 installation directory:

`cp comsol_4.1.0.185_linux.zip [installdir]/comsol41`

where `[installdir]`

is
the root of the installation, for example `/usr/local`

. Unzip it by the
commands:

`cd [installdir]/comsol41`

`unzip -o comsol_4.1.0.185_linux.zip`

If you have not disabled SELinux, run the following command:

`chcon -t textrel_shlib_t [installdir]/comsol41/lib/[platform]/lib*`

where platform is glnx86 or glnxa64.

#### Macintosh

Double-click the downloaded .dmg file to mount the disk image. In the Finder, open the mounted disk and double-click the COMSOL installer icon. Select your COMSOL installation folder, usually called COMSOL41.

### Check your installation

- Start COMSOL Multiphysics.
- On the
**Help**menu, click**About COMSOL Multiphysics**. - Check that the version number is 4.1.0.185 (If not, the installation did not succeed).

## Update Details

#### General

- *Improved stability for selections.
- *Temporary solution files are no longer stored when using a stationary solver.
- Updated documentation and improved translations for supported local languages.
- Several improvements for parametric curves.
- Edge points are now distributed evenly in all cases when meshing.
- GUI display for anisotropic tensors is now more intuitive.
- Several stability issues in GUI, meshing, solving, results analysis, and backward compatibility have been resolved.
- Plot while solving now works as expected in client-server mode, in batch mode, and in the LiveLink™ for MATLAB®.
- Corrected several stability issues, and improved performance.
- Thin Thermally Resistive Layers is now available also in COMSOL without add-on modules.
- Changing default variable names now works as expected.

#### AC/DC Module

- *Corrected impedance matrix calculation for Magnetic and Electric Fields.
- Circuit coupling now works as expected also for the case of more than one coil group feature connected to the circuit.
- The predefined variable for external current density has been corrected.
- Corrected sign error for the Distributed Capacitance feature.
- Particle tracing forces have been corrected for the Magnetic Fields interface.
- A sign error for the remanent flux density in the Magnetic Fields interface has been corrected. Plots for the components now show correct result.
- The variable for the norm of the magnetic flux density has been corrected to now also include the remanent flux density.
- Variables for induced polarization and magnetization are now available.
- Thin Low Permeability Gap now works as expected in 2D and 2D axial symmetry also when solving for out-of-plane magnetic vector potential.

#### Acoustics Module

- Solved stability issue for Aeroacoustics in 2D.

#### Batteries & Fuel Cells Module

- Several stability issues have been fixed. Equations in the Tertiary Current Distribution, Nernst-Planck interface have been corrected.
- The No flux boundary condition is now corrected for the Lithium-ion Battery Interface.
- Several stability fixes and more intuitive interfaces.

#### Chemical Reaction Engineering Module

- Isotropic Diffusion is now available also in the Transport of Diluted Species interface when migration but no convection is used.

#### CFD Module

- Stress calculation when not using the low gas concentration option is now corrected for the Bubbly Flow interface.
- Stability improvement in the memory-efficient formulation.
- Solver defaults for two-phase flow problems have been fine-tuned making it much easier to solve such problems using the default settings.
- Volume Force expressions have been corrected in the Free and Porous Media Flow interface.

#### Chemical Reaction Engineering Module

- Several backward compatibility issues, and stability issues in particular in the Reaction Engineering interface are now resolved.

#### Earth Science Module

- Initial values for poroelasticity now includes the correct variables.

#### Heat Transfer Module

- Streamline diffusion is now corrected for the Heat Transfer interface.
- Several improvements in equation view display and predefined variables.
- The radiation heat source term and the wall term are now consistent with the definition of the radiative intensity for radiation in participating media.
- Wall feature is now added by default if Radiation in Participating Media is enabled.
- Overridden selections in the Heat Transfer in Porous Media interface are now handled correctly.
- Heat Transfer in Thermal Shells now interprets the thermal conductivity correctly for all coordinate systems.
- Improved user interface for Heat Transfer in Porous Media together with Heat Transfer in Fluids.

#### MEMS Module

- Several backward compatibility issues with COMSOL 3.5a have been resolved.

#### Plasma Module

- The Boltzmann Equation interface now works also in client-server mode.

#### RF Module

- *Improved performance for models using multiple ports.
- *Port Boundary Condition is now compatible with Floquet periodic boundary conditions.
- Far-field calculations are now corrected for the case when source boundaries are on the inside of a PML.
- Improved backward compatibility with COMSOL 3.5a for axisymmetric TM waves.
- Loss terms for transient electromagnetic waves have been corrected.
- Improved performance of Far Field calculations, and corrected equations for Far Field symmetry settings.
- A predefined variable for the electric energy density time average, emw.Weav, is now available. The expression for the total energy density, emw.intWe, has also been corrected so that it includes the electric energy in addition to the magnetic energy.

#### Structural Mechanics Module

- *Corrected expression for Boundary Load feature with Load type set to Pressure in the axisymmetric case.
- Principal Stress and Principal Strain vector plots in 2D axisymmetric models now show the correct direction.
- The stability for contact and friction has been improved.
- In the Thermal Stress interface, the display of branch numbers for the Thermal Viscoelastic material has been corrected.
- Shells now work as expected also when a thermal load through the thickness of the shell is applied.
- Geometric Nonlinearity is now available also for the Thermal Stress and Joule Heating and Thermal Expansion interfaces.

* = New in update 3