arXiv subjects

Satyendra K. Tomar

Publications and source records attributed to Satyendra K. Tomar.

3 recordsLinked to original sources

arXiv2014

Guaranteed and Sharp a Posteriori Error Estimates in Isogeometric Analysis

We present functional-type a posteriori error estimates in isogeometric analysis. These estimates, derived on functional grounds, provide guaranteed and sharp upper bounds of the exact error in the energy norm. {Moreover, since these estimates do not contain any unknown/generic constants, they are fully computable, and thus provide quantitative information on the error.} By exploiting the properties of non-uniform rational B-splines, we present efficient computation of these error estimates. The numerical realization and the quality of the computed error distribution are addressed. The potential and the limitations of the proposed approach are illustrated using several computational examples.

math.NA↗

arXiv2014

Condition number estimates for matrices arising in NURBS based isogeometric discretizations of elliptic partial differential equations

We derive bounds for the minimum and maximum eigenvalues and the spectral condition number of matrices for isogeometric discretizations of elliptic partial differential equations in an open, bounded, simply connected Lipschitz domain $Ω\subset \mathbb{R}^d$, $d\in\{2,3\}$. We consider refinements based on mesh size $h$ and polynomial degree $p$ with maximum regularity of spline basis functions. For the $h$-refinement, the condition number of the stiffness matrix is bounded above by a constant times $ h^{-2}$ and the condition number of the mass matrix is uniformly bounded. For the $p$-refinement, the condition number grows exponentially and is bounded above by $p^{2d+2}4^{pd}$ and $p^{2d}4^{pd}$ for the stiffness and mass matrices, respectively. Rigorous theoretical proofs of these estimates and supporting numerical results are provided.

math.NA↗

arXiv2010

A Posteriori Error Estimates for Nonconforming Approximations of Evolutionary Convection-Diffusion Problems

We derive computable upper bounds for the difference between an exact solution of the evolutionary convection-diffusion problem and an approximation of this solution. The estimates are obtained by certain transformations of the integral identity that defines the generalized solution. These estimates depend on neither special properties of the exact solution nor its approximation, and involve only global constants coming from embedding inequalities. The estimates are first derived for functions in the corresponding energy space, and then possible extensions to classes of piecewise continuous approximations are discussed.

math.NA↗