Meshes with different element topologies in gmsh (for Code-Aster)
We have been translating a few Code-Aster verification test manuals into English. The process is not just a straightforward translation of the text in the Fr...
Blog articles
2022
2021
Creating quadrilateral surface meshes with gmsh
The Code-Aster cooling tower modal analysis validation test FORMA11c comes with a quadrilateral mesh provided by Code-Aster. Tips on quadrilateral meshing wi...
Inspecting and manipulating meshes in Salome-Meca for Code-Aster
In this article, I will discuss how elements can be selected from deep inside a 3D mesh in the Salome-Meca environment and manipulated with Python scripts.
2017
Compiling and running the MPM code Vaango on a Cray
Introduction One of the reasons I switched to cmake for my builds was the need to compile my Vaango code on a BlueGene/Q system. The code was previously co...
Unit testing with MPI, googletest, and cmake
Introduction In this article we take a short detour into the problem of continuous unit testing of code that contains MPI calls and use either mpich or Open ...
Parallel domain decomposition for particle methods: Part 4
Introduction The Plimpton scheme of communicating ghost information between patches was described in Part 3 of this series. Let us now see how a similar appr...
Parallel domain decomposition for particle methods: Part 3
Introduction In Part 2 of this series we showed the direct way of communicating ghost particles between patches. That approach requires 26 communication ste...
Parallel domain decomposition for particle methods: Part 2
Introduction The previous article in this series discussed the scatter operation for moving particles to various processes. In this second part of the serie...
Parallel domain decomposition for particle methods: Part 1
Introduction For parallel particle codes that have to be written quickly (while retaining flexibility), the task-based parallelism approach doesn’t always wo...
Can the Larsen-C ice shelf failure be predicted with Peridynamics?
Introduction On July 7, 2017, the Project Midas group released a couple of plots of material velocities and interferograms showing the evolution of a large r...
The difference between the spin and angular velocity tensors
Introduction Several years ago I took created a Wikpedia article on objective stress rates based on lecture notes in nonlinear finite elements for a class th...
The ARENA model for partially saturated soils
Introduction I developed the ARENA model for partially saturated soils last year (2016). Before that we had tried using a typical Drucker-Prager with cap mo...
Material and spatial incremental constitutive equations
The question A colleague asked a question on objectivity a few days ago that had me going back to Ray Ogden’s book on nonlinear elastic deformations. The qu...
Are stresses tensile or compressive during rigid body rotation?
Introduction Recently, I came across a question in StackExchange that pointed out that some books on continuum mechanics suggest that an element will increas...
The CFL condition for explicit discrete element methods:4
Introduction In Part 3 of this article I discussed the approach where the equations for a system of rigid bodies are approximated by a spring-mass system. T...
The CFL condition for explicit discrete element methods:3
Introduction In Part 1 of this article, we revisited the CFL condition and in Part 2 we showed how the CFL condition and the von Neumann stability condition ...
The CFL condition for explicit discrete element methods:2
Introduction In the first part of this article, we looked at the one-dimensional linear second-order wave equation
The CFL condition for explicit discrete element methods:1
Introduction Solutions of hyperbolic partial differential equations using explicit numerical methods need a means of limiting the timestep so that the solu...
Reading XML files containing gzipped data in C++
Introduction We saw how to create an XML file containing compressed particle data in the article “XML format for particle input files”. Let us now explore ho...
Creating an animation with d3.js
Introduction In Part 8 of the series on return algorithms for plasticity we animated the closest-point return algorithm as shown below.
Geometric closest point return algorithm
Introduction In Part 7, we saw that for isotropic elastic materials and perfect associated plasticity, the trial stress and the actual stress are at the shor...
Exploring closest point return plasticity
Introduction In Part 6, I explained why a backward Euler stress update and a closest point return from the trial stress to the yield surface are closely rela...
Nonlinear programming and closest point return plasticity
Introduction In Part 5 I briefly hinted at the closest-point return algorithm. The ideas behind this were made rigorous in the mid-to-late 1980s by a group ...
Forward vs. Backward Euler: Plane stress plasticity
Introduction One of the main points of divergence of many implementations of plastic return algorithms is the choice of the algorithm used for numerical inte...
Plane stress forward Euler Drucker-Prager
Introduction In Part 2 of this series, we saw that a forward Euler return algorithm leads to the discretized equations
Plane stress return: Spectral decomposition
Introduction The previous parts of this series dealt with: Part 1: Background of 3D and plane stress Drucker-Prager plasticity Part 2: A forward Euler ...
The plane stress return algorithm
Introduction In the previous part of this discussion, I derived plane stress expressions for linear elasticity, the Drucker-Prager yield function, and the as...
Plane stress Drucker-Prager return algorithm
Introduction Recently I’ve encountered questions on how the radial return algorithm works when applied to plane stress plasticity. There seems to be some co...
XML format for particle input files
Introduction Let us now change tack slightly and return to an issue I had talked about earlier in Input files: reading XML. Typical input files in research ...
Plotting particles with vtk.js
Introduction In the previous articles in this series we talked about: Part 1: Reading VTK format particles with Javascript in a browser Part 2: Saving ...
Setting up the Three.js ellipsoids
Introduction In the previous articles in this series we talked about:
Setting up the Three.js scene and camera
Introduction In the previous articles in this series we talked about: Part 1: Reading VTK format particles with Javascript in a browser Part 2: Saving ...
Setting up the Three.js renderer
Introduction The previous articles in this series were about: Part 1: Reading VTK format particles with Javascript in a browser Part 2: Saving the read...
Plotting VTK particles with Three.js
Introduction In Part 2 of this series, we showed how the particle data are saved into a Vuex store. Now we are ready to visualize the data. In this article...
Saving particle data in a Vuex store
Introduction In the first part of this series on scientific visualization in Javascript, we saw how data in VTK unstructured grid format produced by C++ simu...
Reading VTK particles in Javascript
In our previous article we discussed the process of calling XML functions in C++ to write data produced by particle simulations in XML format files. These o...
Particle data in VTK XML
In my previous post on writing VTK output files I described how mesh data can be output in VTK XML format. In this article I will talk about how I output par...
Writing VTK XML files in C++
I visualize the output of my simulations using either LLNL’s Visit or Kitware’s ParaView. These tools are wonderful for dealing with large datasets and can ...
Reading JSON in C++
In my previous post on reading XML input files, I discussed how input files can be made more human friendly with XML markup. In some situations, it may be p...
Input files: Reading XML
Mechanics research codes are typically written by graduate students who aim to get their work done as quickly as possible. These codes are not meant to las...
Command pattern for regression testing
A few days ago I had to refactor a 20,000 line class that was being used as a regression tester for discrete element and peridynamics simulations. After som...
Auto-modernizing C++ code
The Clang static analyzer tools come with a handy interface called clang-tidy.
Formatting C++ code
Every once in a while I need to recall how clang-format is set up and run on my Ubuntu 16.04 machine. This post is meant to act as a reminder.
2014
Sampling large data sets (Part 2)
Recall that we had found a set of points that samples a cylindrical domain uniformly. However, these points do not match the locations of our sensors and we...
Sampling large data sets (Part 1)
The amount of data is large. Before we analyze the whole set of data, we can find trends by examining a smaller set of sensors. A smaller set is also usef...