External verification analysis: A code-independent verification technique for unsteady PDE codes

The External Verification Analysis (EVA) code verification technique is developed and presented. An extension of the Method of Manufactured Solutions (MMS), EVA provides a reference solution that can be used to verify both the spatial and temporal discretization schemes of an unsteady PDE solver, without the addition of arbitrary source terms. This feature of EVA allows the code to truly be treated as a “black box” during verification, simplifying the verification procedure. Currently, however, the EVA technique solves the interior equations of a PDE code only – thus the implementation of boundary conditions in the PDE code is not verified. The mathematical foundation of EVA is explained in detail, and the process used to verify a PDE code is discussed. The EVA technique is then demonstrated on a high-order, nonlinear Computational Aeroacoustics code.