A posteriori error estimation

Definition

A posteriori error estimation is a technique used in numerical analysis to evaluate the accuracy of an approximate solution after the solution has been computed. It allows for an assessment of how close the numerical solution is to the true solution by using various estimators derived from the computed solution itself. This method is particularly important in finite element methods, as it provides insight into where the solution may need refinement and helps guide adaptive mesh strategies.

5 Must Know Facts For Your Next Test

1. A posteriori error estimation can help identify regions where the numerical solution has higher error, allowing for targeted mesh refinement in those areas.
2. This method relies on local indicators that assess the quality of the approximation based on the computed solution's gradients and residuals.
3. A posteriori estimates are often more efficient than a priori estimates since they are based on actual computed values rather than theoretical predictions.
4. The reliability of a posteriori error estimation can vary depending on the choice of estimator, making it crucial to select appropriate methods for specific problems.
5. Adaptive finite element methods leverage a posteriori error estimates to dynamically adjust the mesh during computation, leading to improved efficiency and accuracy.

Review Questions

• How does a posteriori error estimation inform adaptive mesh refinement in finite element methods?
  • A posteriori error estimation provides specific information about where the numerical solution may be inaccurate, enabling targeted mesh refinement. By identifying regions with higher estimated errors, practitioners can refine the mesh only in those areas instead of uniformly refining the entire domain. This results in a more efficient use of computational resources and enhances the overall accuracy of the solution.
• Discuss the advantages and disadvantages of using a posteriori error estimation compared to a priori error estimation in numerical solutions.
  • A posteriori error estimation offers several advantages, such as being based on actual computed values, leading to more accurate assessments of error. It also allows for adaptive strategies that can improve efficiency by focusing on areas of high error. However, it can be computationally intensive and may require careful selection of estimators. A priori error estimation, while useful for initial assessments and theoretical analysis, does not reflect actual computation and may lead to less informed refinement strategies.
• Evaluate how a posteriori error estimation impacts the convergence properties of finite element methods.
  • A posteriori error estimation plays a crucial role in improving the convergence properties of finite element methods by providing feedback that informs mesh refinement. By utilizing local error indicators, practitioners can enhance accuracy in critical regions, ultimately leading to faster convergence towards the true solution. Furthermore, this iterative process encourages continuous improvement in approximation quality, which helps ensure that numerical solutions meet desired accuracy standards efficiently.

Related terms

Finite Element Method:

A numerical technique for finding approximate solutions to boundary value problems for partial differential equations by dividing the problem domain into smaller, simpler parts called elements.

Mesh Refinement:

The process of increasing the number of elements in a finite element mesh to improve the accuracy of the numerical solution.

Error Estimator: A mathematical tool used to quantify the difference between the exact and approximate solutions, helping to inform decisions about mesh refinement and overall solution accuracy.