### Abstract

We present and analyze a posteriori error estimates for the local discontinuous Galerkin (LDG) method for the linearized Korteweg-de Vries (KdV) equation in one space dimension. These estimates are computationally simple and are obtained by solving a local steady problem with no boundary condition on each element. We extend the work of Hufford and Xing [J. Comput. Appl. Math., 255 (2014), pp. 441-455] to prove new superconvergence results towards particular projections of the exact solutions for the two auxiliary variables in the LDG method that approximate the first and second derivatives of the solution. The order of convergence is proved to be k + 3/2, when polynomials of total degree not exceeding k are used. These results allow us to prove that the significant parts of the spatial discretization errors for the LDG solution and its spatial derivatives (up to second order) are proportional to (k + 1)-degree Radau polynomials. We use these results to construct asymptotically exact a posteriori error estimates and prove that, for smooth solutions, these a posteriori LDG error estimates for the solution and its spatial derivatives, at a fixed time t, converge to the true errors at O(h^{k+3/2}) rate in the L^{2}-norm. Finally, we prove that the global effectivity indices, for the solution and its spatial derivatives, converge to unity at O(h^{1/2}) rate. Numerical results are presented to validate the theory.

Original language | English (US) |
---|---|

Pages (from-to) | 162-195 |

Number of pages | 34 |

Journal | International Journal of Numerical Analysis and Modeling |

Volume | 12 |

Issue number | 1 |

State | Published - Jan 1 2015 |

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### Keywords

- A posteriori error estimates
- KdV
- Local discontinuous Galerkin method
- Radau points
- Superconvergence

### ASJC Scopus subject areas

- Numerical Analysis

### Cite this

**Asymptotically exact local discontinuous Galerkin error estimates for the linearized Korteweg-de vries equation in one space dimension.** / Baccouch, Mahboub.

Research output: Contribution to journal › Article

}

TY - JOUR

T1 - Asymptotically exact local discontinuous Galerkin error estimates for the linearized Korteweg-de vries equation in one space dimension

AU - Baccouch, Mahboub

PY - 2015/1/1

Y1 - 2015/1/1

N2 - We present and analyze a posteriori error estimates for the local discontinuous Galerkin (LDG) method for the linearized Korteweg-de Vries (KdV) equation in one space dimension. These estimates are computationally simple and are obtained by solving a local steady problem with no boundary condition on each element. We extend the work of Hufford and Xing [J. Comput. Appl. Math., 255 (2014), pp. 441-455] to prove new superconvergence results towards particular projections of the exact solutions for the two auxiliary variables in the LDG method that approximate the first and second derivatives of the solution. The order of convergence is proved to be k + 3/2, when polynomials of total degree not exceeding k are used. These results allow us to prove that the significant parts of the spatial discretization errors for the LDG solution and its spatial derivatives (up to second order) are proportional to (k + 1)-degree Radau polynomials. We use these results to construct asymptotically exact a posteriori error estimates and prove that, for smooth solutions, these a posteriori LDG error estimates for the solution and its spatial derivatives, at a fixed time t, converge to the true errors at O(hk+3/2) rate in the L2-norm. Finally, we prove that the global effectivity indices, for the solution and its spatial derivatives, converge to unity at O(h1/2) rate. Numerical results are presented to validate the theory.

AB - We present and analyze a posteriori error estimates for the local discontinuous Galerkin (LDG) method for the linearized Korteweg-de Vries (KdV) equation in one space dimension. These estimates are computationally simple and are obtained by solving a local steady problem with no boundary condition on each element. We extend the work of Hufford and Xing [J. Comput. Appl. Math., 255 (2014), pp. 441-455] to prove new superconvergence results towards particular projections of the exact solutions for the two auxiliary variables in the LDG method that approximate the first and second derivatives of the solution. The order of convergence is proved to be k + 3/2, when polynomials of total degree not exceeding k are used. These results allow us to prove that the significant parts of the spatial discretization errors for the LDG solution and its spatial derivatives (up to second order) are proportional to (k + 1)-degree Radau polynomials. We use these results to construct asymptotically exact a posteriori error estimates and prove that, for smooth solutions, these a posteriori LDG error estimates for the solution and its spatial derivatives, at a fixed time t, converge to the true errors at O(hk+3/2) rate in the L2-norm. Finally, we prove that the global effectivity indices, for the solution and its spatial derivatives, converge to unity at O(h1/2) rate. Numerical results are presented to validate the theory.

KW - A posteriori error estimates

KW - KdV

KW - Local discontinuous Galerkin method

KW - Radau points

KW - Superconvergence

UR - http://www.scopus.com/inward/record.url?scp=84913557867&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84913557867&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:84913557867

VL - 12

SP - 162

EP - 195

JO - International Journal of Numerical Analysis and Modeling

JF - International Journal of Numerical Analysis and Modeling

SN - 1705-5105

IS - 1

ER -