Experimental Investigation on the Water-Exit Problem of Cylinders Under Various Conditions

This work investigates the water exit problems of slender cylinders under various con-ditions by experiment. The experimental platform is designed with a high-speed pho-tography. 13 experimental cases with varying head shapes, length-to-diameter ratios, ejection velocities, and elastic moduli was conducted to capture water-exit character-istics. The investigation identified ejection velocity as the predominant parameter governing cavity morphology and stability, with higher velocities correlating to in-creased cavity dimensions and reduced drag coefficients. Conical head shape resulted in superior drag reduction characteristics, forming a typical cigar-shaped cavity with clear and regular boundaries. Additionally, an increased length-to-diameter ratio sub-stantially improved drag reduction performance. Material elastic moduli proved cru-cial for water-exit stability, as cylinders with lower moduli experienced severe bending deformation and even trajectory changes, while higher moduli cylinders maintained their form with minimal deformation. This study illuminates the physical mechanisms of slender body water-exit under multi-factor coupling conditions, providing experi-mental evidence and theoretical guidance for cross-media vehicle design and under-water equipment optimization.