Experimental study on the hydrodynamic of foldable-wing unmanned aerial-underwater vehicles during water-exit process

Abstract

The Foldable-Wing Unmanned Aerial-Underwater Vehicle (F-UAUV) demands swift movement over water surfaces at significant pitch angles during the water-exit procedure, a phase highly influenced by strong, non-linear, time-varying hydrodynamic effects. To tackle these complexities, we devised a model experiment scheme mirroring the actual water-exit process. Crafted through structural drainage comparisons, high-fidelity models were developed, complemented by a test platform featuring a double track for accurate evaluations. Subsequent water-exit tests, conducted at various speeds and angles, unveiled a consistent increase in water-exit resistance with speed, peaking at the moment of exit. Concurrently, resultant torque escalated inversely with both speed and angle. Notably, the heightened resistance due to structural drainage exhibited a tendency to stabilize during the latter half of the water-exit process. Utilizing the foundational formula for resistance in a single medium, we proposed an enhanced formula for predicting maximum water-exit resistance, a tool instrumental in facilitating F-UAUV design and powertrain selection. This paper offers an exhaustive analysis of hydrodynamic influences during the water-exit process, serving as a pivotal reference for Unmanned Aerial-Underwater Vehicles development.