## Theory of Current Distribution

##### Edmund Dickinson February 7, 2014

In electrochemical cell design, you need to consider three current distribution classes in the electrolyte and electrodes. These are called primary, secondary, and tertiary, and refer to different approximations that apply depending on the relative significance of solution resistance, finite electrode kinetics, and mass transport. Here, we provide a general introduction to the concept of current distribution and discuss the topic from a theoretical stand-point.

Read More##### Walter Frei February 3, 2014

There are various ways of handling interactions between fluids and solids in COMSOL. You can, for example, explicitly model the fluid using the full Navier-Stokes equations for the pressure and fluid velocity fields. Although that can be a very accurate approach, it’s much more expensive than is needed for certain types of Fluid-Structure Interaction (FSI) problems. Here, we’ll introduce a method for modeling enclosed volumes containing incompressible fluids, under the additional assumption that the momentum and energy transfer via the […]

Read More##### Bettina Schieche January 29, 2014

Integration is one of the most important mathematical tools, especially for numerical simulations. Partial Differential Equations (PDEs) are usually derived from integral balance equations, for example. Once a PDE needs to be solved numerically, integration most often plays an important role, too. This blog post gives an overview of the integration methods available in the COMSOL software and shows you how you can use them.

Read More##### Chandan Kumar January 28, 2014

Here is an interesting question: How can we easily probe the solution at a point that is moving in time, but associated with a stationary geometry? One option is to use the General Extrusion coupling operator. In this blog post, we will take a look at how to use the General Extrusion coupling operator to probe a solution at a point in your geometry, and illustrate how to implement a dynamic probe using an example model.

Read More##### Guest Jeff Crompton January 20, 2014

Today we have the pleasure of introducing Jeff Crompton, a guest author from AltaSim Technologies, who will discuss ceramic matrix composites and how to accurately analyze the production of such an advanced material. Ceramic matrix composites (CMCs) are fast becoming popular in many industries due to their ability to withstand high temperatures, corrosion, and wear better than metal components. They are being used in space applications, burners and combustion chambers, gas turbines, brake discs, and slide bearings. The manufacture of […]

Read More##### Walter Frei January 17, 2014

We often want to model an electromagnetic wave (light, microwaves) incident upon periodic structures, such as diffraction gratings, metamaterials, or frequency selective surfaces. This can be done using the RF or Wave Optics modules from the COMSOL product suite. Both modules provide Floquet periodic boundary conditions and periodic ports and compute the reflected and transmitted diffraction orders as a function of incident angles and wavelength. This blog post introduces the concepts behind this type of analysis and walks through the […]

Read More##### Bjorn Sjodin January 14, 2014

Many of our users are well aware of the fact that COMSOL Multiphysics can be used to solve partial differential equations (PDEs) as well as ordinary differential equations (ODEs) and initial value problems. It may be less obvious that you can also solve algebraic and even transcendental equations, or in other words, find roots of nonlinear equations in one or more variables with no derivatives in them. Are there real applications for this? Absolutely!

Read More##### Walter Frei January 8, 2014

When you are working with foreign CAD data, such as files in STEP or IGES file formats, you may think that you need to re-import a new CAD file and start your modeling over from scratch if you want to study a change in size or shape. But, in fact, you can modify the geometry that you’ve imported with some clever usage of the Deformed Geometry interface in COMSOL Multiphysics. Here, we will look at how this can be done.

Read More##### Nicolas Huc January 6, 2014

In this blog post we will explain the concept of conjugate heat transfer and show you some of its applications. Conjugate heat transfer corresponds with the combination of heat transfer in solids and heat transfer in fluids. In solids, conduction often dominates whereas in fluids, convection usually dominates. Conjugate heat transfer is observed in many situations. For example, heat sinks are optimized to combine heat transfer by conduction in the heat sink with the convection in the surrounding fluid.

Read More##### Mads Herring Jensen January 2, 2014

I recently had the pleasure of preparing a small contribution to the 166th Meeting of the Acoustical Society of America (Fall 2013) together with Wade Conklin and Jordan Schultz from Knowles Electronics. Wade presented our paper entitled “Characterization of a microelectromechanical microphone using the finite element method”. The work consisted of implementing a virtual prototype of a Knowles MEMS microphone (the SPU0409LE5H microphone, see picture below) using COMSOL Multiphysics.

Read More##### Mateusz Stec January 1, 2014

Computer aided engineering (CAE) helps us understand how mechanical systems work before they are physically realized. In order to properly reflect the reality, we continuously increase the modeling complexity when we simulate, validate, or optimize our applications. A simple technique to improve a model is to increase the number of finite elements that in turn create more evaluation points. The hardware and simulation time, however, may limit the size of the model, and other solutions are necessary — such as […]

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