【原创】What is FEMLAB?

harbinliying

FEMLAB is a powerful interactive environment for modeling and solving scientific and engineering problems based on partial differential equations (PDEs). With it you can easily extend conventional models that address one branch of physics to state-of-the art multiphysics models that simultaneously involve multiple branches of science and engineering. However, accessing this power doesn't require that you have in-depth knowledge of mathematics or numerical analysis. Indeed, you can build many useful models by defining the participating physical quantities rather than defining the equations that describe them. Nevertheless, FEMLAB does allow you to create equation-based models. Besides providing these multiple modeling approaches, the software offers multiple ways to harness this power: either through a flexible self-contained graphical user interface (GUI) or from the MATLAB command line.
  
The basic mathematical structure with which FEMLAB operates is a system of partial differential equations. In FEMLAB you can represent PDEs in two ways: coefficient form (suitable for linear or nearly linear problems) or general form (intended for nonlinear problems). Furthermore, it's possible to set up models as stationary or time-dependent, linear or nonlinear, scalar or multicomponent. The package also performs eigenvalue or eigenfrequency analyses.
  
When solving the PDEs that describe a model, FEMLAB applies the finite element method (FEM). The software runs that method in conjunction with adaptive meshing and error control as well as with a variety of numerical solvers. A more detailed description of this mathematical and numerical foundation appears both elsewhere in this manual (see "Overview of PDE Models in FEMLAB" on page 1-170 and "Command-Line Functions" on page 1-226) as well as in the Reference Guide.
  
Due to the fact that PDEs arise in virtually every branch of science and engineering, FEMLAB has an extremely broad applicability and it can model a large number of physical phenomena in many disciplines including:
  
acoustics  
chemical reactions  
diffusion  
electromagnetics  
fluid dynamics  
general physics  
geophysics  
heat transfer  
porous media flow  
quantum mechanics  
semiconductor devices  
structural mechanics  
wave propagation.  
To show how FEMLAB solves familiar or interesting problems in many of these areas, this documentation set includes a Model Library. This separate volume contains an extensive selection of complete, ready-to-run models. Examining them is an excellent way to learn how to work with FEMLAB and see how it applies to the various application areas. Further, you can adapt, expand, or otherwise modify these models to suit your own requirements, so they represent a handy starting point that can save considerable time in many instances.
  
Many real-world applications involve the simultaneous application of PDEs from several areas of science or engineering. Researchers now refer to this type of analysis as multiphysics modeling. For instance, the electrical resistance of a conductor often varies with temperature; thus a model of a conductor carrying current involves thermoelectric effects. This manual introduces you to FEMLAB's unique power in handling multiphysics (see "Multiphysics: Thermo-Electric Effects" on page 1-96 as well as "Multiphysics and Equation-Based Modeling" on page 1-246). Further, the Model Library devotes a separate chapter to the study of several interesting multiphysics examples.
  
Clearly, even in its base configuration FEMLAB offers enormous modeling and analytical power for many disciplines. However, the product has proven particularly useful in several of these areas. Thus we created optional discipline-specific application modules that make it easy to create and analyze models using terminology and solution methods appropriate for those disciplines. We presently offer modules for Structural Mechanics Engineering (SME), Computational Electromagnetics (CEM) and Chemical Engineering (CHEM).
  
Despite all these aids, we recognize that it's impossible to anticipate every possible application area and every user's potential requirements. To give users the ultimate flexibility, the FEMLAB user interface integrates virtually seamlessly to MATLAB, the package that provides the computational engine behind FEMLAB. Indeed, FEMLAB frequently uses MATLAB's syntax and data structures. An enormous benefit of that tight integration is that you can save and export FEMLAB models as MATLAB programs that run directly in that environment or incorporate them with still other products in the MATLAB family. Thus you gain the freedom to combine FEM-based modeling, simulation, and analysis with numerous other techniques in engineering and science. For instance, it's possible to create a finite-element model in FEMLAB and then export it to Simulink or to the Control System Toolbox, where the model becomes an integral part of the simulation of a dynamic system. We refer to such applications of FEMLAB as multidisciplinary.