Opennovation News
Engineering Consulting with Open Source Tools
October, 2008


Opennovation is an engineering consulting firm founded by Adam Powell with a focus on using and helping others to use open source software for design and analysis in engineering disciplines such as mechanics, fluid flow, heat transfer, and chemical reactor design.  Opennovation News is a means of bringing you updates on the company and the broader world of open source software for engineering.

Opennovation News is planning approximately one issue per month.  If you would like to receive it via email, please click here or send email to news@opennovation with "subscribe" in the subject.  Contributions and comments are welcome, please send them to news@opennovation.com.

Contents:

North Shore Technology Council: Sustainable Energy

The North Shore Technology Council (NSTC) October 22 Business Breakfast topic will be "Powering Up Massachusetts' Sustainable Energy Industry".  Opennovation's Adam Powell and NSTC Programming Chair James Kawski are co-producing the panel discussion, which will feature four leaders in the Massachusetts sustainable energy sector:

  • Ian Finlayson is the senior climate policy analyst in the Massachusetts Executive Office of Energy and Environmental Affairs in Boston, where he coordinates the greenhouse gas inventory and forecasts for the state and develops state policy on climate mitigation and related energy sectors.
  • Brad Bradshaw is president of the Massachusetts Hydrogen Coalition.
  • Patrick Quinlan is the associate director of the University of Massachusetts Wind Energy Center.
  • Dr. Roland Schindler is executive director of the recently established MIT-Fraunhofer Center for Sustainable Energy Systems.

Though not directly on-topic for an open source engineering newsletter, engineers and open source enthusiasts who live in the Boston area may find it interesting in several ways.  Panelists are likely to discuss business opportunities, either in manufacturing sustainable energy production equipment, or by incentives for installing local solar and/or wind generation capacity.  A particular theme will be how Massachusetts differentiates itself in this market.  Opennovation has also recently expanded its energy consulting portfolio, making this topic more directly relevant to the company.

NSTC monthly Business Breakfast meetings take place from 7:00-9:00 AM (7:00-8:00 networking, 8:00-9:00 presentation and discussion) at the Peabody Marriott on Centennial Drive.  The cost of attending is $25 for NSTC members and $45 for non-members; individual technology member dues run $75/year.  Though NSTC has not yet chosen Business Breakfast topics for the remainder of the (academic) year, open source software is a likely topic in early 2009.

Product focus: Gmsh

The finite element method (FEM, a.k.a. finite element analysis, FEA) is a very popular technique for calculating the strength of a part, or its heat flow and fluid flow characteristics, etc.  But performing the calculation itself is just one step in that process.  One must first define the shape of the part and divide it into small pieces called a mesh of elements, this set of steps is known as "pre-processing".  And when the calculation is done, it can be a challenge to display the deformations, temperatures, or flow velocity distributions in 3-D in a way which highlights the important features, such as the location where a part is likely to break; this visualization task is known as "post-processing".

Gmsh screenshot

Gmsh is a feature-rich and very mature pre- and post-processor for finite element calculations.  This puts it in the same class as Salomé. It has its own built-in Computer-Aided Design (CAD) engine, and can import files from other CAD programs in the BREP, STEP and IGES formats (if linked with OpenCASCADE). It can generate meshes made of triangles in 2-D or tetrahedra in 3-D, no quadrilaterals, prisms or hexahedra.

You can read a full overview of Gmsh capabilities at the website.  There are also two terrific videos demonstrating Gmsh features, including its CAD engine, meshing capabilities, and several post-processing options and tricks.  Many open source finite element programs, such as deal.II, can import meshes generated by Gmsh.

Finally, the Gmsh user interface can run and control a finite element calculation using the GetDP solver, just as Salomé-MECA can run a simulation using Code_Aster. Salomé-MECA and Code_Aster have more capabilities than Gmsh and GetDP (e.g. quadrilateral and hexahedral element shapes), but the streamlined and consistent interface will make these a great pair of tools for many users.

Gmsh and GetDP both run on Linux, Windows and MacOS (Salomé only distributes a Linux version).

Update: libMesh vs. deal.II

The August "Under the Hood" feature presented the deal.II finite element library, and compared it with libMesh, which was discussed here in May.  The August piece presented many similarities, but did not fully present the differences, between those two libraries, and contained one error.  Because of this, Opennovation News will now revisit that comparison, with the feature list below.

  • Examples: As mentioned in August, the examples are somewhat different; see the August feature for details.
  • C1 elements: The August issue indicated that both can use this type of element to solve fourth-order biharmonic equations.  In fact, only libMesh has this capability (though it is under development for deal.II).  This makes libMesh currently the better library for calculating the bending of a plate under load, and for Cahn-Hilliard phase field simulations of material structure formation.
  • Vector-valued elements: Only deal.II has vector-valued elements (Nédélec, Raviart-Thomas, Arnold-Boffi-Falk, Brezzi-Douglas-Marini etc.), making it the better of the two libraries for some porous flow simulations (e.g. steam driving oil through porous rock), structural mechanics, electromagnetics, etc.
  • Domains with different degrees of freedom: Only deal.II can have different variables, and different numbers of variables, in different groups of elements.  For example, one group of elements can represent a solid with displacement, and another can represent a fluid with velocity and pressure, for fluid-structure interaction simulations such as water flow in a flexible tube.

Finally, both libMesh and deal.II are working to use the Trilinos suite's high-performance parallel solvers and data objects as well as those of PETSc, though most users will not notice those behind-the-scenes libraries—except in performance improvements.

Recent additions to Opennovation.org

The Opennovation.org open source engineering portal has recently expanded in three ways: a new Debian backport repository, a new resources section, and many new products.  The backport repository allows users of the Debian 5.0 "Lenny" Linux distribution (in testing, planned for release later this year) to use packages such as an updated OpenCASCADE, deal.II, etc.  Instructions for using it are at: http://www.opennovation.org/debian/.

The resources section begins with a periodic table contribution from Nicholas Saddock with voluminous reference data including thermodynamic, optical and electrical properties, crystal structure and ionization energies.  This section will add more entries as time goes on.  As with everything open source, contributions are welcome!

New products listed at Opennovation.org include the following:

With Ubuntu 8.10 (October 2008) code-named "Intrtepid Ibex" nearing release, Opennovation.org will soon have a backport repository for that distribution as well.