Quantifying uncertainty in propeller cavitation flow using an implicit large eddy simulation-based verification and validation framework

Abstract

To address the adverse effects of unsteady vortices and cavitation on propeller efficiency and navigational safety at high operating speeds, this study performed numerical simulations of cavitating flow around the marine propeller PC456 using an implicit large eddy simulation (LES) approach coupled with the boundary data immersion method and a local mesh refinement strategy, with five systematically refined meshes. The flow-field characteristics were systematically analyzed. Sheet cavitation developed along the blade leading edges, while tip-vortex cavitation originated near the blade tips and evolved into helical structures in the near wake. Their interaction generated strong local fluctuations in pressure and velocity fields. The wake-vortex system was primarily composed of tip vortices and a hub vortex, with tip vortices dominating the wake dynamics. A verification and validation framework based on implicit LES was established by combining the five-equation method with the safety factor method to quantitatively evaluate numerical and modeling uncertainties in key flow parameters. To address the limitations of the conventional five-equation method, specifically its sensitivity to initial guesses and susceptibility to convergence to local optima in strongly nonlinear cavitating flows, an improved optimization strategy incorporating multiple randomized initial guesses and penalty-term constraints was introduced and applied to the cavitating flow field. The results showed close agreement with experimental measurements in terms of thrust and torque coefficients, while velocity and pressure uncertainties remained within reasonable bounds. The proposed framework provides a quantitative methodology for evaluating cavitating-flow predictions and guiding future engineering applications.