An enhanced validation and verification framework for ventilated cavitation: Decoupling and solving numerical and modeling errors via weighted nonlinear optimization

Background: This study addresses the challenges of quantifying error and uncertainties in unsteady ventilated cavitation flows during the axisymmetric body launches, where conventional Verification and Validation (V&V) methods struggle due to dependencies on asymptotic grid convergence assumptions. Method: Implicit Large Eddy Simulation (ILES) is integrated with the Piecewise linear interface calculation coupling Volume of Fluid (PLIC-VOF) to resolve gas-liquid interactions. An enhanced V&V framework is proposed. By decoupling numerical (δ_N) and modeling errors (δ_M) based on the H2-5 LES theory and introducing three supplementary error estimators (δ_N1[sbnd]N3, δ_M1-M3), the framework overcomes limitations of non-asymptotic data through the minimizing a weighted nonlinear objective function. Result: Experimental validation demonstrates that the enhanced V&V framework achieves the significant reduction of uncertainty within desired margins of ventilated cavitation simulations under transverse flow conditions. Compared to the conventional H2-5 method, the enhanced approach reduces validation uncertainty in the longitudinal velocity component from 10% to 2.7%, effectively suppressing spikes caused by the non-asymptotic data. The unsteady pressure coefficients (C_P) at most times and locations satisfy the validation criterion (|E| < U_V), with all experimental data falling within the uncertainty bounds of Grid 1 simulations. The study reveals that uncertainty in the trailing edge of the body primarily stem from synergistic effects of the unsteady foamy cavity shedding, vortex-cavitation interactions, and phase deviations, providing quantitative insights for further grid optimization and model refinement in high-precision cavitation flow simulations. This framework offers a methodological foundation for error and uncertainty management in strongly unsteady multiphase flow simulations.