How do you establish credibility of CFD results through verification and validation?

CFD verification and validation (V&V) follows AIAA guidelines: Verification ensures equations are solved correctly through code verification (method of manufactured solutions), grid convergence studies (Richardson extrapolation, GCI), iterative convergence, and domain independence. Validation assesses if the right equations are solved by comparing with experiments for relevant flow physics; requires well-documented test cases with uncertainty estimates (e.g., NASA validation databases); and involves metrics like percentage error at specific conditions and statistical validation metrics. Additional considerations include sensitivity analysis, uncertainty quantification (input and model-form), and understanding model limitations for the specific application. Documentation must support regulatory acceptance.