405 research outputs found
A family of quadrilateral finite elements
We present a novel family of quadrilateral finite elements, which
define global spaces over a general quadrilateral mesh with vertices of
arbitrary valency. The elements extend the construction by (Brenner and Sung,
J. Sci. Comput., 2005), which is based on polynomial elements of tensor-product
degree , to all degrees . Thus, we call the family of
finite elements Brenner-Sung quadrilaterals. The proposed quadrilateral
can be seen as a special case of the Argyris isogeometric element of (Kapl,
Sangalli and Takacs, CAGD, 2019). The quadrilateral elements possess similar
degrees of freedom as the classical Argyris triangles. Just as for the Argyris
triangle, we additionally impose continuity at the vertices. In this
paper we focus on the lower degree cases, that may be desirable for their lower
computational cost and better conditioning of the basis: We consider indeed the
polynomial quadrilateral of (bi-)degree~, and the polynomial degrees
and by employing a splitting into or polynomial
pieces, respectively.
The proposed elements reproduce polynomials of total degree . We show that
the space provides optimal approximation order. Due to the interpolation
properties, the error bounds are local on each element. In addition, we
describe the construction of a simple, local basis and give for
explicit formulas for the B\'{e}zier or B-spline coefficients of the basis
functions. Numerical experiments by solving the biharmonic equation demonstrate
the potential of the proposed quadrilateral finite element for the
numerical analysis of fourth order problems, also indicating that (for )
the proposed element performs comparable or in general even better than the
Argyris triangle with respect to the number of degrees of freedom
Mixed Finite Element Formulation of the Biharmonic Equation
We will provide an abstract setting for mixed finite element method for biharmonic equation. The abstract setting casts mixed finite element method for first biharmonic equation and sec- ond biharmonic equation into a single framework altogether. We provide error estimates for both type biharmonic equation, and for the first time an error estimate for the second biharmonic equation
Extreme Learning Machine-Assisted Solution of Biharmonic Equations via Its Coupled Schemes
Obtaining the solutions of partial differential equations based on various
machine learning methods has drawn more and more attention in the fields of
scientific computation and engineering applications. In this work, we first
propose a coupled Extreme Learning Machine (called CELM) method incorporated
with the physical laws to solve a class of fourth-order biharmonic equations by
reformulating it into two well-posed Poisson problems. In addition, some
activation functions including tangent, gauss, sine, and trigonometric
(sin+cos) functions are introduced to assess our CELM method. Notably, the sine
and trigonometric functions demonstrate a remarkable ability to effectively
minimize the approximation error of the CELM model. In the end, several
numerical experiments are performed to study the initializing approaches for
both the weights and biases of the hidden units in our CELM model and explore
the required number of hidden units. Numerical results show the proposed CELM
algorithm is high-precision and efficient to address the biharmonic equation in
both regular and irregular domains
- …