COMSOL Multiphysics Reference Manual

About COMSOL Multiphysics

COMSOL Multiphysics is a powerful interactive simulation environment used to model and solve all kinds of scientific and engineering problems. The software provides a powerful integrated desktop environment with a Model Builder that gives you a full overview of the model and access to all functionality. With COMSOL Multiphysics you can easily extend conventional models for one type of physics into multiphysics models that solve coupled physics phenomena -- and that do so simultaneously. Accessing this power does not require an in-depth knowledge of mathematics or numerical analysis. Using the built-in physics interfaces and the advanced support for material properties, you can build models by defining the relevant physical quantities -- such as material properties, loads, constraints, sources, and fluxes -- rather than by defining the underlying equations. You can always apply these variables, expressions, or numbers directly to solid and fluid domains, boundaries, edges, and points independently of the computational mesh. The COMSOL Multiphysics software then internally compiles a set of equations representing the entire model. You access the power of COMSOL Multiphysics as a standalone product through a flexible graphical user interface (GUI), in applications created using the Application Builder and deployed using COMSOL Compiler™ or COMSOL Server™, or by script programming in Java® or the MATLAB® language (this requires a LiveLink™ for MATLAB® license). Using these physics interfaces, you can perform various types of studies including: Stationary and time-dependent (transient) studies, Linear and nonlinear studies, Eigenfrequency, modal, and frequency response studies. When solving the models, the COMSOL Multiphysics software assembles and solves the problem using a set of advanced numerical analysis tools. The software runs the analysis together with adaptive mesh refinement (if selected) and error control using a variety of numerical solvers. The studies can make use of multiprocessor systems and cluster computing, and you can run batch jobs and parametric sweeps. The COMSOL Multiphysics software creates sequences to record all steps that create the geometry, mesh, physics, studies and solver settings, and visualization and results presentation. This makes it easy to parameterize any part of the model; simply change a node in the model tree and rerun the sequences. The program remembers and reapplies all other information and data in the model.

REAL-WORLD APPLICATIONS

Partial differential equations (PDEs) form the basis for the laws of science and provide the foundation for modeling a wide range of scientific and engineering phenomena. You can use the COMSOL Multiphysics software in many application areas, including the following, combining physics freely and incorporating user-defined PDEs, ODEs, and DAEs if needed:

• Acoustics
• Bioscience
• Chemical reactions
• Corrosion and corrosion protection
• Diffusion
• Electrochemistry
• Electrodeposition
• Electromagnetics
• Fatigue analysis
• Fluid dynamics
• Fuel cells and batteries
• Geophysics and geomechanics
• Heat transfer
• Layered shells and composite materials
• Metal processing
• Microelectromechanical systems (MEMS)
• Microfluidics
• Microwave engineering
• Multibody dynamics
• Optics
• Optimization and sensitivity analysis
• Particle tracing
• Photonics
• Piezoelectric devices
• Pipe flow
• Plasma physics
• Porous media flow
• Quantum mechanics
• Radio-frequency components
• Ray tracing and ray optics
• Rotordynamics
• Semiconductor devices
• Structural mechanics
• Subsurface flow
• Transport phenomena
• Wave propagation

Many real-world applications involve simultaneous couplings of physics, represented in a system of PDEs -- multiphysics. For instance, the electric resistance of a conductor often varies with temperature, and a model of a conductor carrying current should include resistive-heating effects. The Multiphysics Modeling Workflow section discusses multiphysics modeling techniques. Predefined multiphysics interfaces provide easy-to-use entry points for common multiphysics applications.

In its base configuration, COMSOL Multiphysics offers modeling and analysis power for many application areas. For several of the key application areas there are also optional add-on modules. These application-specific modules use terminology, solution methods, and plot types specific to the particular discipline, which simplifies creating and analyzing models. The modules also include comprehensive Application Libraries with example models that show the use of the product within its application areas.

COMSOL Documentation and Help

About the Documentation Set

The full documentation set that ships with COMSOL Multiphysics consists of the following titles:

• Introduction to COMSOL Multiphysics -- information about version 5.5 and how to build models using the desktop environment, including quick references to keyboard shortcuts and common commands and functions.
• COMSOL License Agreement.
• COMSOL Multiphysics Installation Guide -- besides covering various installation options, it describes system requirements and how to configure and run the COMSOL Multiphysics software on different platforms, including client-server architectures as well as shared-memory and distributed (cluster) parallel versions.
• COMSOL Multiphysics Reference Manual -- this book, which covers the functionality of COMSOL Multiphysics across its entire range from geometry modeling to results evaluation and visualization, including the physics interfaces for physics and equation-based modeling. It serves as a tutorial and a reference guide to use COMSOL Multiphysics. This book reviews geometry, mesh, solver, and results functionality and provides detailed information about the settings and options. Additionally, it describes some advanced functionality and settings in COMSOL Multiphysics and provides background material and references.
• COMSOL Multiphysics Programming Reference Manual -- this book provides details about features and techniques that help you control COMSOL Multiphysics using its application programming interface (API). The COMSOL API can be used from the Application Builder, in a standalone Java® application, and from MATLAB® using the LiveLink™ for MATLAB® interface. For the Application Builder, the Application Programming Guide provides information about using the COMSOL API and the API of the Application Builder components to create methods for custom applications.
• The Introduction to the Application Builder and the Application Builder Reference Manual provide documentation related to the Application Builder and how to create and deploy simulation applications and how to use COMSOL Compiler™ to create standalone runnable applications. See also the COMSOL Server Manual for configure a server and clients for COMSOL Multiphysics applications.
• COMSOL Server Manual -- information about setting up, configuring, and running a COMSOL Server for running and deploying applications within an organization.
• The Physics Builder Manual provides documentation related to the Physics Builder for creating custom physics interfaces.
• The Essentials of Postprocessing and Visualization and Specialized Techniques for Postprocessing and Visualization provide tips and information that help you get the most out of the postprocessing and visualization tools in COMSOL Multiphysics.
• COMSOL Multiphysics Release Notes -- information about new functionality and changes in the 5.5 release and about compatibility with earlier versions of COMSOL Multiphysics.

In addition, each of the optional modules includes a manual as described in The COMSOL Multiphysics Modules and Interfacing Options. The documentation for the optional CAD Import Module and LiveLinks to CAD packages is available in separate manuals, and the documentation for the optional Material Library in the Material Library User's Guide. The COMSOL LiveLink™ for MATLAB® User's Guide shows how to access the capabilities of COMSOL from the MATLAB programming environment.

ADDITIONAL INTERNET RESOURCES

• COMSOL website: www.comsol.com
• Contact COMSOL: www.comsol.com/contact
• COMSOL Access: www.comsol.com/access
• Support Center: www.comsol.com/support
• Product Download: www.comsol.com/product-download
• Product Updates: www.comsol.com/support/updates
• COMSOL Blog: www.comsol.com/blogs
• Discussion Forum: www.comsol.com/community
• Events: www.comsol.com/events
• COMSOL Video Gallery: www.comsol.com/video
• Support Knowledge Base: www.comsol.com/support/knowledgebase

The Help Window and Topic-Based Help

The Help window is useful as it is connected to many of the features in the COMSOL Desktop. This concept is called topic-based help or context help. You can also search and access all the HTML documentation content from this window.

To learn more about a node in the Model Builder, or a window on the Desktop, click to highlight a node or window, then press F1. The Help window opens and displays the topic information about the selected feature.

Searching Help and Documentation Content

After you open The Help Window and Topic-Based Help, click the Search button ( ) to open the search engine and search the HTML content. Search results are shown sorted by product. You can also search in the contents of The Documentation Window.

On the Documentation window, you can adjust the Search scope. Enter a search term in the Search expression field and then select All documents, Selected only, or Application libraries from the list to narrow or expand the search scope as needed.

Overview of the Reference Manual

This COMSOL Multiphysics Reference Manual provides comprehensive information about all modeling steps using the COMSOL Multiphysics software. See the individual module manuals for information specific to a specialized module.

As detailed in the section COMSOL Documentation and Help this information can also be searched from the Help system in COMSOL Multiphysics.

ENVIRONMENT

The COMSOL Modeling Environment chapter provides an overview of the COMSOL Multiphysics environment as controlled by the COMSOL Desktop and the tools and windows it provides. Topics include The COMSOL Desktop, The Application Libraries Window, The Physics Interfaces, Creating a New Model, and a key to the icons including links in the Toolbars and Keyboard Shortcuts section.

MODELING

Building a COMSOL Multiphysics Model explains a range of methods and topics including information about the following: details about an introduction to The Model Builder, The Component Node, The Physics Nodes, Selecting Physics Interfaces, Analyzing Model Convergence and Accuracy, Specifying Model Equation Settings, Boundary Conditions, Using Units, Numerical Stabilization, and much more.

CUSTOMIZING THE COMSOL DESKTOP

In the Customizing the COMSOL Desktop chapter, the settings are described related to Customizing a Model, changing Preferences Settings, and details about the Showing More Options.

DEFINITIONS

The Global and Local Definitions chapter describes the global and local (component) definitions features. Depending on the geometric scope, you add the nodes described in this section to either the Global Definitions node or under the Definitions node for a particular component. Topics include Operators, Functions, and Constants, Predefined and Built-In Variables, Mass Properties, Functions, Nonlocal Couplings and Coupling Operators, Coordinate Systems, Identity and Contact Pairs, Probes, and Infinite Elements, Perfectly Matched Layers, and Absorbing Layers.

VISUALIZATION AND SELECTION

The Visualization and Selection Tools chapter describes the tools used to visualize and control how you view models and select parts of the model geometry in the Graphics window and the Settings windows. Important topics include Working with Geometric Entities, Creating Named Selections, and User-Defined Views.

GEOMETRY

The Geometry Modeling and CAD Tools chapter covers geometry modeling in 1D, 2D, and 3D with examples of solid modeling, boundary modeling, Boolean operators, and other CAD tools in COMSOL. In addition, it shows how to use the tools for exploring geometric properties, such as volumes and surfaces. There is also information about using external CAD data. Topics include Creating a Geometry for Analysis, Working with Geometry Sequences, Geometric Primitives, Geometry Operations, and Virtual Geometry and Mesh Control Operations.

MESH

The Meshing chapter summarizes how to create and control your mesh for 1D, 2D, and 3D geometries in the COMSOL Multiphysics software. It also explains these topics, which include: Creating a Mesh for Analysis, Meshing Techniques, Meshing Operations and Attributes, and Importing and Exporting Meshes.

MATERIAL

The Materials chapter introduces you to the material databases included with the COMSOL products. Topics include a Materials Overview, Working with Materials, Material Properties Reference, User-Defined Materials and Libraries, Using Functions in Materials, and Module-Specific Material Databases.

AC/DC

The AC/DC Interfaces chapter explains the physics interfaces available for modeling electromagnetics, which you find under the AC/DC branch when adding a physics interface. It also contains sections about general fundamentals and theory for electric fields.

ACOUSTICS

The Pressure Acoustics Interface chapter describes how to use the Pressure Acoustics, Frequency Domain interface, found under the Acoustics branch when adding a physics interface, for modeling and simulation of acoustics and vibrations.

CHEMICAL SPECIES TRANSPORT

The Chemical Species Transport Interfaces chapter explains how to use the Transport of Diluted Species interface, found under the Chemical Species Transport branch when adding a physics interface, to model and simulate mass transfer by diffusion and convection based on Fick's law of diffusion.

FLUID FLOW

The Fluid Flow Interface chapter explains how to use the Laminar Flow interface, found under the Fluid Flow>Single-Phase Flow branch when adding a physics interface, to model and simulate fluid mechanics for laminar, incompressible fluids.

HEAT TRANSFER

The Heat Transfer Interfaces chapter describes the different types of Heat Transfer interfaces (Heat Transfer in Solids and Heat Transfer in Fluids), and the Joule Heating interface, all found under the Heat Transfer branch when adding a physics interface.

SOLID MECHANICS

The Solid Mechanics chapter explains how to use the Solid Mechanics interface, found under the Structural Mechanics branch when adding a physics interface, to simulate and analyze applications involving solid mechanics. The physics interface is used for stress analysis and general solid mechanics simulation.

EQUATION-BASED MODELING

The Equation-Based Modeling chapter describes the use of the mathematics interfaces, found under the Mathematics branch when adding a physics interface, which are used for equation-based modeling. With those interfaces you can solve various types of PDEs using different formulations. You can also solve ODEs and other global equations, add events and curvilinear coordinates, compute sensitivities, and add moving interfaces and deforming meshes.