## Using General Extrusion Operators to Model Periodic Structures

##### Walter Frei August 11, 2015

In the course of building multiphysics models, we often encounter situations in which the solution to one physics is periodic — or very nearly so — while the solutions to other physics of interest are nonperiodic. If we know this ahead of time, it is possible to exploit the periodicity to reduce computational requirements. Here, we will demonstrate how to accomplish this using the General Extrusion component couplings in COMSOL Multiphysics.

### Computing Design Sensitivities in COMSOL Multiphysics

##### Walter Frei August 5, 2015

One useful — but in my experience, rarely used — capability available within COMSOL Multiphysics is the ability to compute design sensitivities. Assuming that you have a single objective function that is computed based on your finite element model, you can easily compute how sensitive this objective function is with respect to any model input, using only the core COMSOL Multiphysics package. In this blog post, we will look at how to use this functionality.

### Tracking Material Damage with the Previous Solution Operator

##### Walter Frei July 21, 2015

When modeling a manufacturing process, such as the heating of an object, it is possible for irreversible damage to occur due to a change in temperature. This may even be a desired step in the process. With the Previous Solution operator, we can model such damage in COMSOL Multiphysics. Here, we will look at the “baking off” of a thin coating on a wafer heated by a laser.

### Guide to Frequency Domain Wave Electromagnetics Modeling

##### Walter Frei June 30, 2015

Over the last several weeks, we’ve published a series of blog posts addressing the various domain and boundary conditions available for wave electromagnetics simulation in the frequency domain; as well as modeling, meshing, and solving options. In this blog post, I will tie all of this information together and provide an introduction to the various types of problems that you can solve in the RF and Wave Optics modules.

### Using the Previous Solution Operator in Transient Modeling

##### Walter Frei June 25, 2015

COMSOL Multiphysics version 5.1 includes a Previous Solution operator within time-dependent studies. This operator allows you to evaluate quantities at the previous time step when using the default implicit time-stepping algorithm. Let us take a look at how this operator is implemented and then examine how it can be used for various modeling needs.

### Modeling Laser-Material Interactions in COMSOL Multiphysics

##### Walter Frei June 22, 2015

A question that we are asked all of the time is if COMSOL Multiphysics can model laser-material interactions and heating. The answer, of course, depends on exactly what type of problem you want to solve, as different modeling techniques are appropriate for different problems. Today, we will discuss various approaches for simulating the heating of materials illuminated by laser light.

### Simulation Tools for Solving Wave Electromagnetics Problems

##### Walter Frei June 18, 2015

When solving wave electromagnetics problems with either the RF or Wave Optics modules, we use the finite element method to solve the governing Maxwell’s equations. In this blog post, we will look at the various modeling, meshing, solving, and postprocessing options available to you and when you should use them.

### Modeling of Materials in Wave Electromagnetics Problems

##### Walter Frei May 27, 2015

Whenever we are solving a wave electromagnetics problem in COMSOL Multiphysics, we build a model that is composed of domains and boundary conditions. Within the domains, we use various material models to represent a wide range of substances. However, from a mathematical point of view, all of these different materials end up being handled identically within the governing equation. Let’s take a look at these various material models and discuss when to use them.

### Modeling Metallic Objects in Wave Electromagnetics Problems

##### Walter Frei May 14, 2015

Metals are materials that are highly conductive and reflect an incident electromagnetic wave — light, microwaves, and radio waves — very well. When using the RF Module or the Wave Optics Module to simulate electromagnetics problems in the frequency domain, there are several options for modeling metallic objects. Here, we will look at the Impedance and Transition boundary conditions as well as the Perfect Electric Conductor boundary condition, offering guidance on when to use each one.

### Which Module Should I Choose for Working with My CAD Data?

##### Walter Frei April 14, 2015

There are several different add-on modules to the COMSOL MultiphysicsÂ® software for working with external CAD and ECAD data. These modules allow both unidirectional and bidirectional data transfer between the COMSOL Multiphysics analysis tools and the CAD and ECAD software that you are using for design. In this blog post, we will cover the functionality of these various modules and describe why you may want to use them.

### Modeling Laser-Material Interactions with the Beer-Lambert Law

##### Walter Frei April 13, 2015

High-intensity lasers incident upon a material that is partially transparent will deposit power into the material itself. If the absorption of the incident light can be described by the Beer-Lambert law, it is possible to model this power deposition using the core functionality of COMSOL Multiphysics. We will demonstrate how to model the absorption of the laser light and the resultant heating for a material with temperature-dependent absorptivity.