## How to Model the Optical Properties of Rough Surfaces

##### Walter Frei June 6, 2017

Whenever light is incident on a dielectric material, like glass, part of the light is transmitted while another part is reflected. Sometimes, we add a metal coating, such as gold, which alters the transmittance and reflectance as well as leads to some absorption of light. The dielectric surface and the metal coating also often have some random variations in height and thickness. In this blog post, we will introduce and develop a computational model for this situation.

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### How to Create a Randomized Geometry Using Model Methods

##### Walter Frei June 5, 2017

Have you ever wanted to include a randomly created geometry in your model? Perhaps you want to simulate a natural material or an arrangement of parts that has some known statistical distribution of dimensional variations. In such cases, we may want to create a random geometry in the COMSOL Multiphysics® software. With the release of version 5.3, we can now create random geometries using a model method. Let’s take a look at how to do so with a tasty example.

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### 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.

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### Computing the Band Gap in Superlattices with the Schrödinger Equation

##### Chien Liu May 31, 2017

You can use the new Schrödinger Equation interface for modeling with the Semiconductor Module in the latest release of the COMSOL® software. Let’s look at a simple example app that uses this interface to estimate the electron and hole ground state energy levels for a superlattice structure. By building apps like this one, device engineers are able to calculate the band gap for a given periodic structure and adjust the design parameters until a desired band gap value is achieved.

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### Studying Stress in Threaded Pipe Fitting Designs from CAD Assemblies

##### Bridget Cunningham May 30, 2017

Every year, over 40 million fire sprinkler systems are fitted worldwide. These systems are effective due to their piping designs, which are resistant to high heat and mechanical damage. A popular choice for such designs is threaded steel pipe. But analyzing a complex pipe design is challenging because of the detailed geometry. What approach can we take to efficiently combine accurate geometrical designs with reliable stress analyses? Version 5.3 of the COMSOL® software offers functionality for this purpose.

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### Efficiently Optimizing Solar Dish Receiver Designs

##### Caty Fairclough May 29, 2017

When designing a solar dish receiver, you may need to rerun your simulation multiple times to find an optimized design iteration. To save time, you can build an app that enables you to rapidly test different geometries and more easily create improved designs. Let’s explore a new simulation app in COMSOL Multiphysics® version 5.3, the Solar Dish Receiver Designer, which you can use as inspiration for building apps of your own.

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### Analyzing Critical Speeds with the Rotor Bearing System Simulator

##### Prashant Srivastava May 25, 2017

Rotating components are important elements in machines such as gas turbines, turbochargers, pumps, compressors, electric generators, and motors. Designing such a component requires studying its critical speed, which is the speed at which the amplitude of the vibration in the system becomes large — often leading to failure. Let’s explore how to find the critical speeds for a wide range of rotors via the Rotor Bearing System Simulator, created using the COMSOL Multiphysics® software.

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### Benchmark Model Shows Reliable Results for Inertial Focusing Analysis

##### Bridget Cunningham May 24, 2017

Inertial focusing is a useful technique for various applications, particularly within the medical field. Ensuring its effectiveness requires accurately describing the migration of particles as they flow through a channel. Version 5.3 of the COMSOL Multiphysics® software gives you the tools to generate reliable results that agree with experimental data on inertial focusing. Our new benchmark model highlights these capabilities.

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### How to Model Gearbox Vibration and Noise in COMSOL Multiphysics®

##### Pawan Soami May 23, 2017

Gears are used in a variety of applications, such as clocks, industrial machinery, music boxes, bicycles, and automobiles. A gearbox is a major source of vibration and noise irrespective of how it is used. The most effective approach to reduce the noise radiation from a gearbox is to perform a vibroacoustic analysis to improve the design. Let’s see how the COMSOL Multiphysics® software can be used to help build quieter transmission systems.

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### How to Analyze Eigenfrequencies That Change with Temperature

##### Henrik Sönnerlind May 22, 2017

In some applications, particularly within the MEMS field, it is important to study the sensitivity of a device’s eigenfrequencies with respect to a variation in temperature. In this blog post, we show how to do this using COMSOL Multiphysics® version 5.3. We also explore effects like stress softening, geometric changes, and the temperature dependence of material properties.

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### Studying the Artificial Ground Freezing Method with Simulation

##### Bridget Cunningham May 18, 2017

When the German engineer F. H. Poetsch first developed the artificial ground freezing (AGF) method in 1883, he did so to avoid water within Belgian coal mines. The method, which first received praise in the late 1800s, remains similar to its original form and is still valuable today. To develop a more effective AGF method, we can turn to simulation analyses.

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