## How to Generate Random Surfaces in COMSOL Multiphysics®

##### Bjorn Sjodin June 2, 2017

To easily generate random-looking geometric surfaces, the COMSOL Multiphysics® software provides a powerful set of built-in functions and operators, such as functions for uniform and Gaussian random distributions and a very useful sum operator. In this blog post, we show you how to generate a randomized surface with what amounts to a “one liner” expression with detailed control of the constituent spatial frequency components that determine the nature of the surface’s roughness.

Read More##### Temesgen Kindo May 17, 2017

Sometimes a simulation runs longer than needed, not giving us a way to monitor intermediate results or stop conditionally. This can leave us staring at the monitor, ready to pounce. In this blog post, we discuss how to automate this process in the COMSOL Multiphysics® software. This way, we can work on something else while the software checks the conditions after each step. We also have the option to see what happens the first time the conditions are violated.

Read More##### Hanna Gothäll May 12, 2017

Creating a suitable mesh for your FEA simulations is crucial for getting accurate results. In this blog post, we discuss how to check entities reported in mesh warnings and errors, how to view the statistics of a mesh or parts of a mesh, as well as how to plot the mesh and mesh-specific quantities and delimit these plots to selected regions.

Read More##### Magnus Ringh May 10, 2017

If you’re looking for ways to manage multiple solutions, version 5.3 of the COMSOL Multiphysics® software offers several new tools for doing so. These include options for combining two solutions into one; storing solutions in different data sets so that they can be postprocessed and analyzed individually; and joining solutions to, for example, compare them. In this blog post, we will look at how to use these new tools.

Read More##### Temesgen Kindo May 9, 2017

When your simulations consume significant memory, do you buy a bigger computer? When they take too long to solve, do you just run them overnight? Often, you don’t have another option. But sometimes, if you have the right tools, you can find a better approach by exploiting the mathematical structure. Today, we will show you how to use the so-called maximum principles to save computational resources and time in the COMSOL Multiphysics® software.

Read More##### Amelia Halliday May 8, 2017

When making improvements to a model in the COMSOL Multiphysics® software, you are likely to add more parameters and variables. As the complexity of your model grows, it can become difficult to keep track of where these parameters are being used and defined, as well as to recall them for use in the settings of other nodes. In this blog post, we show you how to use the Auto Completion and Find tools for efficient model setup.

Read More##### Walter Frei April 4, 2017

Have you ever wanted to query the results of your model within an arbitrary geometric subregion? You might think that this requires adding geometries to a model and recomputing the solution. Instead, in the COMSOL Multiphysics® software, we can just add and reposition a part solely for the purpose of evaluating the results. We will demonstrate this in the context of computing mutual inductance between coils and discuss simpler techniques that can be used for a reduced set of cases.

Read More##### Walter Frei March 2, 2017

Have you ever modeled deforming objects in the COMSOL Multiphysics® software and wanted to know the distance between them? In today’s blog post, we will look at how to compute distances between objects using methods for determining the closest distance field. We’ll also find out how to use the distance field as a part of a multiphysics model.

Read More##### Yosuke Mizuyama February 27, 2017

We previously learned how to calculate the Fourier transform of a rectangular aperture in a Fraunhofer diffraction model in the COMSOL Multiphysics® software. In that example, the aperture was given as an analytical function. The procedure is a bit different if the source data for the Fourier transformation is a computed solution. In this blog post, we will learn how to implement the Fourier transformation for computed solutions with an electromagnetic simulation of a Fresnel lens.

Read More##### Caty Fairclough February 21, 2017

The COMSOL Multiphysics® software includes many built-in physics equations and interfaces, but there may be times when you need to implement physics that aren’t part of the software to solve your modeling problem. You can use the flexibility of the COMSOL® software to add user-defined equations via equation-based modeling. Today, we discuss using equation-based modeling to solve a shallow water equation, which can be used to analyze coastal erosion.

Read More##### Andrew Griesmer February 7, 2017

The Open Recovery File feature is a somewhat unknown feature in the COMSOL Multiphysics® software, but it’s useful for anyone running simulations that give multiple solutions. If, for any reason, the software shuts down before the simulation finishes, you can open a recovery file so that you don’t lose your work. Here, we highlight a tutorial video on how to open these files to recover “lost” work as well as go over the strengths and limitations of this feature.

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