Multiphysics treats simulations that involve multiple physical models or multiple simultaneous physical phenomena. For example, combining chemical kinetics and fluid mechanics or combining finite elements with molecular dynamics. Multiphysics typically involves solving coupled systems of partial differential equations.
Many physical simulations involve coupled systems, such as electric and magnetic fields for electromagnetism, pressure and velocity for sound, or the real and the imaginary part of the quantum mechanical wave function. Another case is the mean field approximation for the electronic structure of atoms, where the electric field and the electron wave functions are coupled.
Single Discretization Method
Advanced Simulation Library, Elmer and MOOSE are examples of open source software packages for simulating multiphysics models. Abaqus, ADINA, Altair, ANSYS Multiphysics, Code_Aster, CFD-ACE+, CFD-FASTRAN, COMSOL Multiphysics, FEATool Multiphysics, FlexPDE, LS-DYNA, NEi Nastran, and OOFELIE  are some examples of commercially available software packages. These software packages mainly rely on the Finite Element Method or similar commonplace numerical methods for simulating coupled physics: thermal stress, electromechanical interaction, fluid structure interaction (FSI), fluid flow with heat transport and chemical reactions, electromagnetic fluids (magnetohydrodynamics or plasma), electromagnetically induced heating. In many cases, to get accurate results, it is important to include mutual dependencies where the material properties significant for one field (such as the electric field) vary with the value of another field (such as temperature) and vice versa.
Multiple Discretization Methods
There are cases where each subset of partial differential equations has different mathematical behavior, for example when compressible fluid flow is coupled with structural analysis or heat transfer. To perform an optimal simulation in those cases, a different discretization procedure must be applied to each subset. For example, the compressible flow is discretized with a finite volume method and the conjugate heat transfer with a finite element analysis. fluidyn-MP is one of the example of commercially available software package for simulating Multiphysics engineering problems using Multiple Discretization Methods.
- "Advanced Simulation Library".
- "Elmer - CSC". CSC — IT Center for Science Ltd. Retrieved 2010-06-24.
- "ADINA Multiphysics".
- "Altair Smart Multiphysics".
- "ANSYS Multiphysics". ANSYS, Inc. Retrieved 2008-10-30.
- "Code_Aster". EDF.
- "COMSOL Multiphysics". COMSOL, Inc. Retrieved 2009-05-30.
- "FEATool Multiphysics". Precise Simulation, Ltd. Retrieved 2014-07-17.
- "Oofelie". Open Engineering. Retrieved 2010-01-20.
- "fluidyn-MP". FLUIDYN. Retrieved 2012-06-11.
- Susan L. Graham, Marc Snir, and Cynthia A. Patterson (Editors), Getting Up to Speed: The Future of Supercomputing, Appendix D. The National Academies Press, Washington DC, 2004. ISBN 0-309-09502-6.
- Paul Lethbridge, Multiphysics Analysis, p26, The Industrial Physicist, Dec 2004/Jan 2005, 
- : An easy to use Octave and Matlab Multiphysics Toolbox
- MOOSE (Multiphysics Object Oriented Simulation Environment) - Open source simulation framework by Idaho National Laboratory
- SALOME platform - SALOME : Open source platform for multi-physics and simulation
- The OpenPALM coupler : an open source high performances dynamic parallel coupler by CERFACS
- ELMER - ELMER : Open source Finite Element Software for Multiphysical Problems has a Graphic interface ElmerGUI
- MpCCI : MpCCI - Multiphysics Code Coupling Interface