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The Rayleigh–Ritz method is often used in mechanical engineering for finding the approximate real resonant frequencies of multi degree of freedom systems, such as spring mass systems or flywheels on a shaft with varying cross section. It is an extension of Rayleigh's method.
This variational characterization of eigenvalues leads to the Rayleigh–Ritz method: choose an approximating as a linear combination of basis functions (for example trigonometric functions) and carry out a finite-dimensional minimization among such linear combinations. This method is often surprisingly accurate.
In quantum mechanics, the variational method is one way of finding approximations to the lowest energy eigenstate or ground state, and some excited states. This allows calculating approximate wavefunctions such as molecular orbitals. [1] The basis for this method is the variational principle. [2] [3]
The Rayleigh–Ritz method for solving boundary-value problems in elasticity and wave propagation; Fermat's principle in geometrical optics; Hamilton's principle in classical mechanics; Maupertuis' principle in classical mechanics; The principle of least action in mechanics, electromagnetic theory, and quantum mechanics; The variational method ...
In 1909 Ritz developed a direct method to find an approximate solution for boundary value problems. It converts the often insoluble differential equation into the solution of a matrix equation. It is a theoretical preparatory work for the finite element method (FEM). This method is also known as Ritz's variation principle and the Rayleigh-Ritz ...
This suggests that the normal vibrations of an object (Fig. 1) may be calculated by applying a variational method (in our case the Rayleigh-Ritz variational method, explained in the next paragraph) to determine both the normal mode frequencies and the description of the physical oscillations. [4]
They are useful when we use the Galerkin method or Rayleigh-Ritz method to find approximate solutions of partial differential equations modeling vibrations of structures such as strings and plates; the paper of Courant (1943) [2] is fundamental. The Finite element method is a widespread particular case.
Galerkin method — a finite element method in which the residual is orthogonal to the finite element space Discontinuous Galerkin method — a Galerkin method in which the approximate solution is not continuous; Rayleigh–Ritz method — a finite element method based on variational principles; Spectral element method — high-order finite ...