Multiphysics accompanies mechatronics

  • 06-Apr-2009 11:13 EDT
Comsol Engine Image.JPG

An engine with an electromagnetic valvetrain system was modeled using Comsol’s multiphysics capabilities. The model of the two magnets (upper right) used in the valvetrain shows the phi component of the magnetic potential.

While engineering groups are bringing together different disciplines to solve the growing need for mechatronics solutions, they may also need new interdisciplinary engineering tools to capture multiphysics.

Multiphysics is the simultaneous solution of a problem requiring differing models. They are needed to simulate adequately, for example, battery problems where electrical, chemical kinetics, and heat transfer are all needed. “There is a need for every product today to meet new, edge-of-the-envelope performance,” said Bruce Jenkins, a principal with Ora Research. “It is not nice-to-have, you must have [ever better performance] or you will not be chosen, either by the consumer or by an OEM or even by regulatory authorities.” In some cases, achieving this better performance requires a multiphysics approach.

Comsol first offered its multiphysics solution over 10 years ago. Designed architecturally for simultaneous solution of multiple physics, it specializes in combined solutions from continuum mechanics models. Ease of use is stressed. Users define their own physical problems with equations they write or they select predefined ones already built-in. It hides the nitty-gritty of FEA mathematics as much as possible. With a variety of electrical, MEMS, mechanical, chemical, and optimization solvers built in, Comsol also boasts interoperability with most popular CAD programs. It imports models from Autodesk Inventor, SolidWorks, CATIA, Pro/Engineer, NX, and SolidEdge. The available Material Library contains data for more than 2500 materials, or users can import their own. It also imports FEA meshes created in other programs. Additional flexibility includes a bidirectional interface with Matlab and Simulink as well as input from Matweb, MIMICS, and Simpleware. For chemical reaction software, it interfaces with Chemkin, Cape-open, and JANAF, according to the company. There is a lot for a potential user to digest.

In automotive, the applications that Bjorn Sjodin, Vice President of Applications, cites as the best fit for Comsol includes batteries and fuel cells, including steam reforming fuel cells. These require simultaneous solving of electric current, transport of chemicals and weakly compressive Navier-Stokes fluid flow. Other applications he cites include design and simulation of diesel particulate filters, acoustic-structural interactions such as body-boom, and corrosion modeling. Given the difficulties in modeling the effect of corrosion on fatigue strength, Sjodin is “waiting for someone to couple fatigue and corrosion, something Comsol can do.” Other applications he cites include mode analysis of crankshaft, acoustics in a perforated muffler, various electromechanical devices that couple electromagnetic, heating and structural deformation among other potential applications.

One of the keys to their approach is a single, combined, generalized error term that spans all the physics of a particular problem. The error term is automatically computed and if the solution does not converge, Comsol issues a warning. “As desktop computers have become so much more powerful in the last five years, these complex multiphysics solutions have become practical,” said Sjodin.

Other companies that offer multiphysics solutions include Ansys Inc. and CD-Adapco.

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