## 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.

Read More##### 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.

Read More##### 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.

Read More##### 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.

Read More##### 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.

Read More##### 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.

Read More##### 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.

Read More##### Lexi Carver | June 8, 2015

In recent posts, we have covered a variety of plot types used for postprocessing simulation results in COMSOL Multiphysics and the ways that they can help you understand and share your results. Now let’s take a look at some tricks to simplify work in the graphics window.

Read More##### 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.

Read More##### Chien Liu | April 16, 2015

Previously in our weak form series, we discretized the weak form equation to obtain a matrix equation to solve for the unknown coefficients in our simple example problem. Following the same procedure as in this previous blog post, we will implement the equation in the COMSOL Multiphysics® software with additional steps included to examine the matrices. We will find it more convenient to use a COMSOL® software application to display all relevant matrices at once, arranged logically on one screen.

Read More##### 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.

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