A hybrid turbulence model for the taxiing seaplane

Accurate prediction of aerodynamic and hydrodynamic loads, as well as attitude, during high-speed seaplane taxiing is hindered by the strong nonlinear interaction between air and water flows across the free surface and the multiphase nature of the problem. To address this challenge, we propose a hybrid turbulence framework (SRH, Spalart–Allmaras + Realizable k–ε hybrid turbulence model) based on Reynolds-averaged Navier–Stokes (RANS)/RANS coupling, in which the computational domain is partitioned into a liquid-dominant region, a gas-dominant region, and an interfacial transitional zone. Distinct turbulence closures are assigned to the single-phase regions, while a phase-volume-fraction-based transition scheme ensures smooth parameter exchange across the interface. Validation against experimental measurements and single-model RANS simulations demonstrates that the SRH model achieves comparable accuracy at low speeds, and at high speeds reduces the mean prediction error by ∼5% relative to the single-model baseline, with up to 30% improvement in drag prediction accuracy at the highest volume Froude number (Fr▽) considered. This framework improves both aerodynamic force estimation and the resolution of aerodynamic–hydrodynamic interactions, offering a computationally efficient and physically consistent approach for high-speed multiphase flow prediction in aeronautical and marine engineering applications.