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All posts by Walter Frei

Meshing Your Geometry: When to Use the Various Element Types

November 4, 2013

In a previous blog entry, we introduced meshing considerations for linear static problems. One of the key concepts there was the idea of mesh convergence — as you refine the mesh, the solution will become more accurate. In this post, we will delve deeper into how to choose an appropriate mesh to start your mesh convergence studies for linear static finite element problems.

How to Identify and Resolve Singularities in the Model when Meshing

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 […]

Meshing Considerations for Linear Static Problems

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.

Solving Linear Static Finite Element Models

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.

Using Global Equations: Modeling Room Air Temperature in a House

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.

Computational Electromagnetics Modeling, Which Module to Use?

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 […]

A Finite Element Modeling Book Review

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 […]

Using Gradient-Free Optimization

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 […]