All posts by Walter Frei

Walter Frei | October 29, 2013

In our previous post on Meshing Considerations for Linear Static Problems, we found that, in the limit of mesh refinement, the solution to the finite element model would converge toward the true solution. We also saw that adaptive mesh refinement could be used to generate a mesh that would have smaller elements in regions where the error was higher, rather than simply using smaller elements everywhere in the model. In this post, we will examine a couple of common pitfalls […]

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Walter Frei | October 22, 2013

In this blog entry, we introduce meshing considerations for linear static finite element problems. This is the first in a series of postings on meshing techniques that is meant to provide guidance on how to approach the meshing of your finite element model with confidence.

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Walter Frei | October 15, 2013

In this first blog entry of our new solver series, we describe the algorithm used to solve all linear static finite element problems. This information is presented in the context of a very simple 1D finite element problem, but is applicable for all cases, and is important for understanding more complex nonlinear and multiphysics solution techniques to be discussed in upcoming blog posts.

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Walter Frei | September 20, 2013

An interesting question came up the other day that I felt would make an excellent blog post since it allows us to discuss one of the very powerful, and often underutilized, features of COMSOL Multiphysics: the Global Equation. In this post, we will look at using global equations to introduce an additional degree of freedom to a model. This additional degree of freedom will represent something we do not want to model explicitly.

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Walter Frei | September 16, 2013

COMSOL Multiphysics offers several different formulations for solving turbulent flow problems: the Spalart-Allmaras, k-epsilon, k-omega, Low Reynolds number k-epsilon, and SST models. All of these formulations are available in the CFD Module, and the k-epsilon and Low Reynolds number k-epsilon are available in the Heat Transfer Module. This posting outlines the reasons why we want to use these various turbulence models, how to choose between them, and how to use them effectively. Throughout the post, you’ll find links to relevant […]

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Walter Frei | September 10, 2013

A question we get asked all of the time is: “Which of the COMSOL products should be used for modeling a particular electromagnetic device or application?” There are currently six modules labeled as “Electrical” in the product suite; the AC/DC Module, RF Module, Wave Optics Module, MEMS Module, Plasma Module, and Semiconductor Module. The first four address applications purely governed by various forms of Maxwell’s equations, while the Plasma Module addresses the coupling of electromagnetic fields to plasma transport and […]

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Walter Frei | August 30, 2013

Recently, I was given a copy of the book Finite Element Modeling Methods for Photonics, by B.M. Azizur Rahman and Arti Agrawal. This book proved to be a good companion to the RF Module and Wave Optics Module for graduate students starting in photonics and new users of COMSOL who would like a very targeted introduction to the field. The website accompanying the book comes with some sample computer codes used by the authors in simulation that readers can use […]

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Walter Frei | August 23, 2013

The COMSOL Conference 2013 will be a great opportunity for you to learn about the use of the COMSOL Multiphysics® family of products. Today, I’ll talk a little bit about the various minicourses, how they fit together, and how you can decide which minicourses to attend.

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Walter Frei | August 2, 2013

The COMSOL Optimization Module includes both gradient-based and gradient-free optimization techniques. Whereas the gradient-based optimization method can compute an exact analytic derivative of an objective function and any associated constraint functions, it does require these functions to be smooth and differentiable. In this blog post, we examine the use of the gradient-free optimizer, which can consider objective function and constraints that are not differentiable or smooth. The dimensions of a spinning wheel are optimized to reduce the mass while maintaining […]

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Walter Frei | June 20, 2013

The Coplanar Waveguide (CPW) is commonly used in microwave circuits. COMSOL Multiphysics, with the RF Module, makes it easy to compute the impedance, fields, losses, and other operating parameters needed when designing a CPW.

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Walter Frei | April 2, 2013

A question that comes up occasionally is whether or not you can compute the inductance of a single straight wire. This seemingly simple question actually does not really have an answer, and gives us the opportunity to talk about a very interesting point when solving Maxwell’s equations. Anybody working in the field of computational electromagnetics should have an understanding of this key concept, as it will help you properly set up and interpret models involving magnetic fields.

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