Question

How is the discretization error found?

(a) Difference between the solutions obtained from systematically refined grids

(b) Difference between the exact and the numerical solutions

(c) Difference between the exact solution and the solution from the refined grid

(d) Difference between the coarse grid solution and the exact solution

The question was posed to me in an internship interview.

Query is from Errors in Finite Difference Approximations topic in section Finite Difference Methods of Computational Fluid Dynamics

Answer 1

The correct choice is (a) Difference between the solutions obtained from systematically refined grids

To elaborate: Discretization error is originally the difference between the exact solution of the partial differential equation and the solution of the algebraic equation. But, as the exact solution is not known, we estimate the discretization error as the difference between the solutions obtained from systematically refined grids.