## How to Implement a Point Source with the Weak Form

##### Chien Liu | August 24, 2015

Today we continue our discussion on the weak formulation by looking at how to implement a point source with the weak form. A point source is a useful tool for idealizing the situation where a source is concentrated in a very small region of the modeling domain. We will find that it is very convenient to set up such a point source using the weak form.

##### 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.

##### Temesgen Kindo | July 27, 2015

How do we check if a simulation tool works correctly? One approach is the Method of Manufactured Solutions. The process involves assuming a solution, obtaining source terms and other auxiliary conditions consistent with the assumption, solving the problem with those conditions as inputs to the simulation tool, and comparing the results with the assumed solution. The method is easy to use and very versatile. For example, researchers at Sandia National Laboratories have used it with several in-house codes.

##### Wei Guo | July 2, 2015

Component coupling operators are a useful set of tools included in COMSOL Multiphysics. They can be used to derive numerical values, create new coordinate systems, and link different components in the same model. In this blog post, we will explore yet another possibility: Using General Extrusion, one of the component coupling operators, to extract local solution data and postprocess effectively.

##### 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.

##### 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.

##### 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.

##### 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.

##### 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.

##### Lexi Carver | April 28, 2015

When simulating acoustic waves, vibrating mechanical hardware, or fluid in a channel — just to name a few applications — you may be interested in visualizing the movement or shape change in a device. Postprocessing and visualization can help enhance your understanding of simulation results, and using plots to illustrate physical motion allows you to put everything into perspective. Deformations are a great way to accomplish this.