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Finite element method

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The finite element method (FEM) is a powerful numerical technique used to solve complex mathematical problems. It is specifically designed to solve partial differential equations (PDEs) that arise in engineering and physics. These equations describe how things change across space and time. Engineers use FEM to study structural analysis, heat transfer, fluid flow, and electromagnetism. Because these problems are often too difficult to solve with exact formulas, computers perform the necessary calculations. High-speed supercomputers are often required to handle the largest and most complex simulations.

FAE visualization
FAE visualization

To solve a large problem, FEM uses a process called discretization. This involves subdividing a large, complex system into much smaller, simpler parts called finite elements. This process creates a numerical domain known as a mesh, which consists of a finite number of points. Dividing a system into subdomains offers several technical advantages. It allows for an accurate representation of complex geometries and the inclusion of dissimilar material properties. It also makes it easier to represent the total solution and capture local effects within the system.

Finite element triangulation
Finite element triangulation

The mechanism of FEM follows a specific sequence of mathematical steps. First, the original problem is divided into subdomains, each represented by a set of element equations. These element equations are simpler versions that locally approximate the original, complex partial differential equations. In many cases, FEM is viewed as a special case of the Galerkin method. This involves constructing an integral of the inner product of a residual and weight functions. The goal is to minimize the approximation error by fitting trial functions into the PDE. The process eliminates spatial derivatives, resulting in algebraic equations for steady-state problems or ordinary differential equations for transient problems.

Once the element equations are created, they must be reassembled. This second step involves generating a global system of equations by transforming coordinates from local nodes to global nodes. This spatial transformation includes making orientation adjustments relative to a reference coordinate system. The simple equations from each element are then assembled into one massive system that models the entire problem. Computers use known solution techniques to solve this global system and obtain a numerical answer.

Finite element sparse matrix
Finite element sparse matrix

History shows that FEM grew from the need to solve structural analysis problems in civil and aeronautical engineering. Its roots can be traced to the early 1940s with the work of Alexander Hrennikoff and Richard Courant. Hrennikoff used a lattice analogy to discretize domains, while Courant divided domains into triangular sub-regions. Courant's work helped solve equations related to the torsion of a cylinder. Other pioneers included Ioannis Argyris and Leonard Oganesyan. In the late 1950s, Feng Kang independently rediscovered the method in China while calculating dam constructions.

Piecewise linear function2D
Piecewise linear function2D

The method gained significant momentum during the 1960s and 1970s. Various research groups at institutions like the University of Stuttgart, UC Berkeley, and Swansea University contributed to its development. During this era, NASA sponsored the original version of the NASTRAN program. In 1969, the Norwegian society Det Norske Veritas developed Sesam for ship analysis. A rigorous mathematical foundation for the method was finally established in 1973 by Gilbert Strang and George Fix.

Vanadis a1 test
Vanadis a1 test

Today, the practical application of FEM is known as finite element analysis (FEA). FEA is a vital computational tool that allows engineers to test physical systems without building expensive prototypes. For example, in a frontal car crash simulation, engineers can increase prediction accuracy at the front of the car while reducing it at the rear to save costs.

FAE visualization
FAE visualization

This method is also used in numerical weather prediction. It is especially useful for modeling highly nonlinear phenomena, such as tropical cyclones in the atmosphere or eddies in the ocean.

Finite element solution
Finite element solution

By using FEM, scientists can model everything from oil pipelines to the complex mechanics of a human knee joint.

Human knee joint FE model
Human knee joint FE model
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🖼️ Images & Media (9)
File:FAE visualization.jpg
FAE visualization.jpg
File:Finite element method 1D illustration1.svg
Finite element method 1D illustration1.svg
File:Piecewise linear function2D.svg
Piecewise linear function2D.svg
File:Finite element triangulation.svg
Finite element triangulation.svg
File:Finite element sparse matrix.png
Finite element sparse matrix.png
File:Finite element solution.svg
Finite element solution.svg
File:Vanadis a1 test.gif
Vanadis a1 test.gif
File:Vanadis a2 test.gif
Vanadis a2 test.gif
File:Human knee joint FE model.png
Human knee joint FE model.png
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