Verification and Validation

Topics
	Verification test cases
	Verification test cases descriptions and results.
	Validation test cases
	Validation test cases descriptions and results.

Detailed Description

Verification and Validation {#doc_page_verification_validation}

Verification and validation of a CFD code are essential steps in establishing a reliable numerical tool. These concepts are extensively discussed in [1] and [2], and are more broadly addressed in [3] Notus CFD is thoroughly verified and validated thanks to an important amount of numerical test cases and adequate processing tools. They are separated into two main topics, Verification and Validation:

• Verification is the process of determining whether the implementation of a model and its associated methods accurately represents its conceptual description and solution. The fundamental strategy of verification involves the identification, quantification, and reduction of errors in the numerical model and its solution. Code verification encompasses solution verification on a set of problems for which the exact solution (available only for simplified problems) is known or manufactured. The latter does not necessarily require a connection with the reality of a physical phenomenon. Verification thus offers evidence that the continuous model is correctly solved by the discrete approach chosen in the calculation code. It is primarily a mathematical and computational process.
• Validation is the process that assesses the extent to which a numerical model accurately represents a physical phenomenon for the purpose of utilizing the results. It entails comparing precise numerical solutions with experimental (or theoretical) results. It’s important to note that validation doesn’t assume the experimental measurements are inherently more accurate than the numerical solutions; rather, it considers them as the most adequate means available for representing the reality in the context of validation. Benchmarking the numerical solutions obtained with different codes is also a crucial component of the validation process.

When installing Notus CFD, the first step is to verify and validate that the version compiled on your hardware and sofware produce the expected results - see run notus guide. This script runs a collection of NTS files that cover most of the modeling and numerical methods of the code.

Most NTS files are sufficient to describe a case, but for some test cases, particular work is done in Fortran files compiled after the Notus library compilation. The directory src/notus/test_cases contains these Fortran files. Please refer to the developer's V&V page for more details.

References

[1] W. Oberkampf and T. Trucano. Verification and Validation in Computational Fluid Dynamics. 2002. doi: 10.2172/793406.

[2] C. J. Roy. Review of code and solution verification procedures for computational simulation. Journal of Computational Physics, 205(1):131156, 2005. doi: 10.1016/j.jcp.2004.10.036.

[3] P.J. Roache. Verification and Validation in Computational Science and Engineering. Hermosa Publishers, 1998. ISBN 9780913478080.