## Computing the Impedance of a Corrugated Waveguide

##### Walter Frei | March 25, 2014

It is well-known that you can use the RF Module to compute the impedance of lossless transmission line structures, such as coaxial cables of uniform cross section. But did you know that you can also compute an effective impedance for waveguides with non-uniform cross section? Let’s find out how!

Read More##### Andrew Griesmer | March 24, 2014

Born 179 years ago today, Josef Stefan was a brilliant Austrian physicist who studied radiation. He is credited with empirically deriving the relationship between the radiant energy of a blackbody and its temperature, known as the Stefan-Boltzmann law.

Read More##### Pär Persson Mattsson | March 20, 2014

One thing we haven’t talked much about so far in the Hybrid Modeling blog series is what speedup we can expect when adding more resources to our computations. Today, we consider some theoretical investigations that explain the limitations in parallel computing. We will also show you how to use the COMSOL software’s Batch Sweeps option, which is a built-in, embarrassingly parallel functionality for improving performance when you reach these limits.

Read More##### Valerio Marra | March 18, 2014

What do heated soap bubbles, wavy clouds, and Jupiter’s Great Red Spot have in common? Their formation depends on the dynamics of the shear layer existing between two parallel streams moving at different velocities. This unstable motion, called Kelvin-Helmholtz instability, is ubiquitous and plays an important role in the dynamics of climate, for example. Let’s take a closer look at the onset and evolution of this instability with the help of Computational Fluid Dynamics (CFD) analysis.

Read More##### Fanny Littmarck | March 14, 2014

Branch line couplers, a type of 90-degree or quadrature hybrid coupler, are popular because they are simple to fabricate and easy to design. They are passive devices commonly used in single-antenna transmitter systems and I/Q signal splitters/combiners. Let’s look at the basics of how this type of coupler works and some of its important design aspects.

Read More##### Lexi Carver | March 12, 2014

Have you ever wondered why boaters wear polarized sunglasses? It’s because sunlight reflecting off the water is primarily polarized in one direction, and polarized sunglasses will block this component of the reflected light, thus reducing glare. To understand why this is, we can use COMSOL software. This example solves the governing Maxwell’s equations using the RF Module or Wave Optics Module to simulate light incident at an angle upon a dielectric medium, and the solution shows agreement with analytic solutions.

Read More##### Mark Fowler | March 21, 2014

When designing magnets, you want to save resources by using as little material as possible, while generating as large of a force as possible on the object in question. To calculate the force of a one-sided magnet, you can use COMSOL Multiphysics and the AC/DC Module.

Read More##### Lexi Carver | March 19, 2014

Using the Graphics window in COMSOL Multiphysics can be a little tricky if you’re not too familiar with what it can do. But once you know the shortcuts, controlling the camera and view angles to create good graphics becomes quite straightforward. I hope the techniques shown here will help you produce graphics to visualize and present your work more easily.

Read More##### Alexandra Foley | March 17, 2014

When modeling computationally taxing geometries, you can save time by using cyclic symmetry to cut down on memory usage. This can be more complex for rotationally than axially symmetric geometries. However, with the Structural Mechanics Module you can easily solve a single section of an impeller model and still get accurate results.

Read More##### Eyal Spier | March 13, 2014

While the mathematical study of chemical reactions has been performed for more than a century, it is only fairly recently that the computational tools for numeric integration of rate equations have been widely available. The old adage of “necessity is the mother of all invention” holds true in this instance. Here, you will find a classical analysis of a non-trivial reaction system, and learn how the simplified solution compares with the “real” one.

Read More##### Nancy Bannach | March 11, 2014

A lot of materials have anisotropic properties and, in many cases, the anisotropy follows the shape of the material. COMSOL Multiphysics offers different methods for defining curvilinear coordinate systems. Here, we discuss the concepts of each and when to use which method.

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