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All posts by Temesgen Kindo

Exploiting Maximum Principles to Save Time and Resources

May 9, 2017

By exploiting maximum principles in large and complex models, you will save time and computational resources without having to buy a bigger computer or leave your model to solve overnight.

Integrals with Moving Limits and Solving Integro-Differential Equations

October 6, 2016

In a previous blog post, we discussed integration methods in time and space, touching on how to compute antiderivatives using integration coupling operators. Today, we’ll expand on that idea and show you how to analyze spatial integrals over variable limits, whether they are prescribed explicitly or defined implicitly. The technique that we will describe can be helpful for analyzing results as well as for solving integral and integro-differential equations in the COMSOL Multiphysics® software.

Guidelines for Equation-Based Modeling in Axisymmetric Components

October 5, 2016

Cylindrical coordinates are useful for efficiently solving and postprocessing rotationally symmetric problems. The COMSOL Multiphysics® software has built-in support for cylindrical coordinates in the axisymmetry physics interfaces. When defining custom partial differential equations (PDEs) using the mathematical interfaces, paying close attention to their meaning is important. The PDE interfaces assume partial differentiation in a Cartesian system, requiring manual coordinate transformations to change to a cylindrical system. See how to account for such coordinate transformations when using your own PDEs.

How to Reuse a Deformed Shape as a Geometry Input

September 1, 2016

Suppose you take a piece of metal — a thin sheet, for example — and apply some mechanical loads. The metal will deform and take on a new shape that differs from the original undeformed configuration. Say you now want to use this deformed object as part of a new geometry construction. You can then solve another physics problem on the new composite domain. Today, we’ll demonstrate how to use a deformed object as an input to a geometry sequence.

How to Integrate External Data Files with Your COMSOL® App

August 30, 2016

Have you ever wanted to integrate your COMSOL® software apps with external data files? These files can contain material properties, geometric dimensions, or other model inputs, and such data can derive from internal company standards or be provided by a vendor. Built-in methods in the Application Builder simplify reading from these files and displaying options read. To show this procedure, we will build an app that populates a combo box with material properties from a comma-separated values (CSV) file.

Part 2: Mapping Variables with General Extrusion Operators

October 5, 2015

Previously on the blog, we introduced you to Linear Extrusion operators and demonstrated their use in mapping variables between a source and a destination. This approach, as explained earlier, is limited to cases in which the source and destination are related by affine transformations. Today, we will discuss General Extrusion operators, which are designed to handle nonlinear mappings and the mapping of variables between geometric entities of different dimensions.

Accessing Nonlocal Variables with Linear Extrusion Operators

September 29, 2015

In many simulation tasks, it is necessary to transfer variables from one region of a computation domain (the source) to another region or component (the destination). In COMSOL Multiphysics, this functionality is achieved by defining a point-to-point map, called an extrusion operator, that relates a set of destination points with a set of source points. Once a mapping is established by an extrusion operator, all variables defined at the source can be accessed from the destination using the same operator.

Verify Simulations with the Method of Manufactured Solutions

July 27, 2015

How do we check if a simulation tool works correctly? One approach is the Method of Manufactured Solutions. The process involves assuming a solution, obtaining source terms and other auxiliary conditions consistent with the assumption, solving the problem with those conditions as inputs to the simulation tool, and comparing the results with the assumed solution. The method is easy to use and very versatile. For example, researchers at Sandia National Laboratories have used it with several in-house codes.

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