All posts by Walter Frei
Solving Linear Static Finite Element Models
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.
Using Global Equations: Modeling Room Air Temperature in a House
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.
Computational Electromagnetics Modeling, Which Module to Use?
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 […]
A Finite Element Modeling Book Review
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 […]
Using Gradient-Free Optimization
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 […]
Modeling of Coplanar Waveguides
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.
Computing the Inductance of a Straight Wire
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.
Using Point Cloud Data in Your COMSOL Model
There is sometimes a need to include data from other simulation packages into a COMSOL Multiphysics model. There are a variety of ways in which this can be done, but one of the easiest approaches is to read in the point cloud data via a spreadsheet format text file. In this blog post, we walk through the steps of reading in such data, and using it in a COMSOL model.
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