Experimental investigation on kinematic characteristics and slamming loads of a free-fall lifeboat model entering into water

Abstract

The rapid immersion of free-fall lifeboats into water produces intense slamming forces, directly affecting the safety of onboard personnel. The study carried out a series of experimental drop tests using lifeboat models. A 4 × 4 array of pressure sensors was positioned on the lower surface of the lifeboat's bow, a gyroscope and an accelerometer were installed within the lifeboat. The research investigates the distribution law of slamming loads at the bow, and change law of attitude angle and acceleration during water entry. To explore the influence of initial slide parameters on water entry velocity and attitude, an adjustable sliding test device was designed, allowing for variations in slide angle, length, and drop height. Additionally, an image recognition system was developed to capture the motion trajectory, attitude, and velocity before water entry. A 0.78 % error margin was determined by comparing identified attitude angles with gyroscopic data, confirming the system's reliability and accuracy. The findings indicate that increasing the lifeboat's slide angle from 30° to 60° significantly reduces the peak slamming pressure, and the maximum slamming pressure coefficient C_p occurs at 0.24 L_OA in front of the center of gravity.