All COMSOL^® software products undergo stability improvements that are introduced as updates. The following list contains the most important improvements in COMSOL^® version 5.4 update 4 (including those of update 1, update 2, and update 3).

COMSOL Multiphysics^®

• Fixed an issue with radio buttons being unresponsive in the Model Builder for macOS.¹
• Fixed an issue where applications would fail to launch on long running instances.²
• Improved the implementation so that report file paths supplied by the user during method calls are stored in the model.²
• Made performance improvements for long parametric sweeps.²
• Fixed a problem where file resources could be lost when computing in the Test Application window.²
• Fixed an issue causing the settings for subnodes of PDE interfaces to not be included in reports when requested.³
• Added support for adaptation in the Stationary Source Sweep study.³
• COMSOL Multiphysics^® version 5.4 is the last COMSOL^® version to support the Red Hat^® Enterprise Linux^® 6.³
• Made various stability and performance improvements.¹,²,³
• External materials no longer trigger multiple license key checkouts.⁴
• Increased the robustness of COMSOL Client over WAN connections.⁴
• Fixed a potential deadlock when connecting to a server using the COMSOL API or LiveLink™ for MATLAB^®.⁴
• The page layout settings (such as page size, margins, orientation, and columns) of a specified custom Microsoft^® Word^® template file are now used when writing reports in Microsoft^® Word^® format.⁴
• Fixed a bug that prevented writing a report from method code to a file specified in a file browser dialog box when using the default security settings.⁴
• Fixed a problem where the MUMPS solver might crash or hang during cluster simulations.⁴

COMSOL Server™

• Fixed an issue with the COMSOL Server™ installer on localized Windows^® versions.¹
• Fixed an issue where replaced applications failed to launch on secondary servers.²
• Implemented more robust handling of server-side network timeouts.²
• Added support for filtering and sorting to COMSOL Client for Android™.³
• Fixed a layout issue with the COMSOL Server™ footer in Chrome™ 72+.⁴

COMSOL Compiler™

• Renamed the Executable button and the corresponding Settings window to Compiler.¹
• Renamed the Compile button, used for compiling applications, to Create Executable.¹

AC/DC Module

• Added sensitivity analysis support to the Terminal feature, applicable to the Electric Currents, Electrostatics, Electrostatics, Boundary Elements, and Magnetic and Electric Fields interfaces.²
• The Coil feature in the Magnetic Fields interface now supports an a priori prescribed, spatially dependent conductivity when using the Single conductor setting.²
• Made various usability improvements.²
• The Electric Currents, Single Layer Shell interface is now visible in the AC/DC section of the Model Wizard, making it easier to find when creating new models.³
• Made stability improvements for the computation of contact impedance losses in the frequency domain.³
• Improved magnetic coenergy density support.³

Acoustics Module

• Corrected the global postprocessing variables generated by the Port condition in 2D axisymmetric models.¹
• Fixed an issue when only one frequency was used in a study together with the Port Sweep functionality.¹

CFD Module

• Corrected the density and viscosity used for the Inlet boundary condition in the Darcy's Law interface when used with the Multiphase Flow in Porous Media multiphysics coupling node.¹
• Corrected the implementation for the use of multiple Mass Source nodes in the Phase Transport interface.¹
• Made various stability improvements.²

Chemical Reaction Engineering Module

• Corrected the heat capacity ratio (Cp/Cv) function from the Thermodynamics interface.²
• Corrected the Thermodynamics density function for the Ideal gas model. The derivatives with respect to the species mass fractions are now correctly evaluated.³
• A new setting to control the convection is introduced in flux boundary conditions for mass transport. This setting is used to ensure backward compatibility for models created in previous versions.³

Composite Materials Module

• Fixed a problem where, in the Layered Shell interface, spurious stresses could appear in elements with large variations in normal orientation. This issue, which could occur for imported meshes or together with virtual geometry operations, is now fixed.²
• Fixed an issue in the Layered Shell interface, where the total thickness (lshell.d) would be erroneously computed if the layers on a certain boundary were not all selected in the same Linear Elastic Material node.⁴

ECAD Import Module

• Improved the implementation so that the vertical faces are now included in boundary net selections for drill layers in ODB++ files.¹
• Fixed an issue that prevented ODB++ files with several steps to import correctly.³

Fatigue Module

• The use of auxiliary sweeps in fatigue computations has been improved.³
• Critical plane evaluations in the Fatigue Module are now more robust for cases where all stress or strain states are close to proportional to each other. Previously, the predicted fatigue life could be overly conservative in such situations.³

Heat Transfer Module

• Fixed the isobaric compressibility coefficient definition when user-defined density is used.¹
• Fixed moving mesh support in the shell features.¹
• Enabled Surface-to-Surface Radiation multiphysics coupling for the Slip Flow and High Mach Number Flow interfaces.¹
• Corrected the expression for Zmean (mean figure of merit) in the Thermoelectric Effect multiphysics coupling.¹
• Fixed the out-of-plane thickness contribution to heat flux interface features in 2D geometries.¹
• Corrected diffusive heat flux postprocessing variables definition when employing the Heat Transfer with Radiative Beam in Absorbing Media multiphysics coupling.²
• Corrected the ambient temperature definition in the Ambient Thermal Properties node when the Temperature list is set to either User-defined coefficient for deviation or User-defined correction.²
• Corrected coefficients of a few Legendre polynomials of order higher than 4.²
• Fixed out-of-plane thickness to unity and disabled out-of-plane features when a multiphysics coupling involving a radiation interface is active.²
• Fixed out-of-plane thickness contribution for turbulent nonisothermal flow with wall functions or automatic wall treatment.²
• Fixed the Opaque Surface feature for the Radiative Beam in Absorbing Media interface.²
• Fixed density definition in the Phase Change Material node when it is used under the Solid feature with a moving mesh.²
• Removed redundant selection filter in the postprocessing dataset of a layered material in order to obtain more concise models.²
• Defined overriding between the Irreversible Transformation and Phase Change Material subfeatures.²
• Fixed an issue with the mass flow rate definition in the Interior Fan feature.²
• Fixed the definition of energy balance postprocessing variables in cases with a multiphysics coupling defining heat sources on boundaries.²
• Fixed the thermal conductivity definition in the Phase Change Material node when it is used under the Solid feature with a moving mesh.²
• Fixed a migration issue for models containing Heat Transfer with Radiation in Participating Media interfaces built in version 5.3a and earlier.²
• Updated the thermal conductivity definition when different material properties are specified for the damaged tissue in the Thermal Damage subfeature.²
• Canceled contribution of work done by pressure changes for incompressible flow with Boussinesq approximation for the Nonisothermal Flow interface.²
• Removed the possibility to define an out-of-plane thickness in heat transfer interfaces in 1D, 2D, and 2D axisymmetric geometries when heat transfer is coupled with a radiation interface.²
• Added display of the radiation direction in the Prescribed Radiosity feature.²
• Fixed contribution of Equilibrium Discharge Heat Source, Electromagnetic Heating, Electrochemical Heating, Ray Heating, and Geothermal Heating features to the residual variable.³
• Improved performance of models that use the Surface-to-Surface Radiation interface.³
• Surface-to-surface radiation: Corrected diffuse irradiance contribution for models with multiple spectral bands.³
• Fixed the override of layered material definitions in Porous Medium features in the Heat Transfer in Shells interface.³
• Added support for thermal conductivity tensor definitions when using a moving frame combined with user-defined coordinate systems.³
• Fixed Ambient Settings description in automatic report generation.³
• Fixed continuity condition for relative humidity on pairs in the Moisture Transport interface.³
• Removed erroneous mesh suggestions generated by the Continuity feature for shells.⁴

LiveLink™ for SOLIDWORKS^®

• Added functionality so that the LiveLink™ interface and the embedded one-window simulation environment now support SOLIDWORKS^® 2019.¹

LiveLink™ for PTC Creo Parametric™

• Fixed an issue where selections defined in components sometimes would not be loaded into the assembly.³

MEMS Module

• Corrected the equation display for the Heaviside step function.⁴

Nonlinear Structural Materials Module

• Corrected an error in the Souza-Auricchio model for shape memory alloys.¹
• Corrected a problem when a user-defined creep law was created using a Potential in the Creep node. In previous versions, a factor of two was applied to the off-diagonal terms in the potential expression in order to account for the symmetry in the stress tensor. This factor was based on the assumption that the potential expression was written in terms of only the upper-diagonal parts of the stress tensor. With this update, the potential is assumed to be written on a standard form, so that the shear strain rates are directly computed as the derivative of the potential with respect to corresponding stress tensor element.¹

Particle Tracing Module

• Fixed a problem so that the Heat Source, Convective Heat Losses, and Radiative Heat Losses features for the Particle Tracing for Fluid Flow interface now respect domain selections.¹
• Improved handling of diffuse scattering or emission of particles or rays from interior boundaries.²
• Corrected the coefficient in the Saffman lift force to account for a corrigendum to the original Saffman paper.²
• Added auxiliary dependent variables on particles to the Add/Replace Expression menu during results processing.²
• Fixed a bug where the Thermal Re-Emission boundary condition and the Inlet with the Thermal velocity distribution did not initialize an out-of-plane particle velocity.³
• Fixed an error when two or more Accumulator features are used to compute a vector quantity, such as volume force or current density, on different domains.³
• Allowed the Thermal Re-Emission boundary condition and the Thermal velocity distribution to use a Common Model Input for surface temperature or couple the surface temperature to a field variable previously solved for.³
• Corrected an error when the Thermal Re-Emission boundary condition was used together with the Accumulator subnode.³
• Fixed some inconsistency in the assignment of units for the Auxiliary Dependent Variable feature.⁴
• The variable for "Total number of particles released by feature" now gives the correct solution in models that also have secondary particle emission.⁴
• Two or more instances of Magnetophoretic Force are now allowed to be applied to different species in the same model.⁴

Pipe Flow Module

• Made improvements so that Pipe Connection features in old models that use the Nonisothermal Pipe Flow interface will import as is, with a warning that the feature is obsolete and will be removed in future versions.¹

Plasma Module

• Changed the functionality so that the Boltzmann Equation, Two-Term Approximation interface is now only available in 0D components. The old version, which was available in 1D, is now retired. Existing models using the 1D version of the interface can still be opened and modified.²

Ray Optics Module

• Implemented additional safeguard against division by zero errors when using the Ray Termination feature.¹
• Improved the functionality to set automatically the frequency model input for refractive indices that depend on ray frequency or wavelength. If you had previously set the model input manually, for example to comp1.gop.f0, then, after updating, go to Common Model Inputs, right-click Frequency (Hz) -minput.freq, and choose Reset to Default.¹
• Fixed an error in the Grating feature when Compute Power is selected from the physics interface's Intensity Computation list.³

Semiconductor Module

• Corrected the equation display for Poisson's equation in the Semiconductor interface.¹
• Fixed an issue with the time derivative weak term for the quasi-Fermi level formulation.³
• Fixed missing safeguard for square root of negative number for the variable g_red0, which is used in the Kane 4-band model for the matrix element computation in the Optical Transitions feature.³

Structural Mechanics Module

• Fixed an error that could occur when adding Adhesion in a Solid Mechanics interface that already contains a Plasticity node.¹
• Fixed an error that could occur when using Compact History in a model containing a Solid-Beam Connection multiphysics coupling.¹
• Improved performance for postprocessing with Shell datasets.²
• Corrected an error occurring during the generation of default solver sequences for multiphysics models that contain a Damage node in the Solid Mechanics interface.²
• Included losses from the Thin-Film Damping feature when computing power dissipation and quality factor in the Solid Mechanics interface.²
• Made stability improvements.²
• Corrected an error in the Plate interface where it was not possible to enter initial values for all degrees of freedom from the user interface.³
• Corrected a problem where the Augment for rigid response check box in the settings for a response spectrum dataset was not responsive.³
• Corrected an error occurring when the values of the total reaction force variables were wrong if a load was applied on a Rigid Connector in which the soft formulation had been selected.⁴
• Corrected an error occurring when the Activation feature was combined with geometric nonlinearity in a 2D axisymmetric model.⁴

Subsurface Flow Module

• Corrected the definition of the Permeability and Kozeny-Carman formulation for Richards' equation to use the relative permeability for calculating the transmissibility.¹
• Corrected velocity contribution due to gravity with specified acceleration for the Fracture Flow feature.²
• Corrected a problem in the 1D Darcy's Law interface when changing the cross-sectional area to something other than 1 m².³

¹ New in update 1 ² New in update 2 ³ New in update 3 ⁴ New in update 4