THE MOVEMENT OF THE FREEFALL LIFEBOAT WHEN DESCENDING FROM THE INCLINED RAMP

Abstract

The article provides a brief overview of the history of the creation and development of freefall lifeboats (FFLB), designed for the urgent safe evacuation of people from sea vessels and offshore oil platforms in case of accidents in extreme weather conditions.

The problem of FFLB movement, which is modeled by a homogeneous rod, is considered when descending from the inclined ramp during the first phase of the fall with an increasing angle of inclination (tangage) – from the moment when the center of the masses of the boat is above the edge of the support (extreme roller of the ramp) until the moment of rise from the ramp of the end of the supporting surfaces of the loop. The differential equations of motion in polar coordinates are composed using the Lagrange equations of the second kind. The solver system of ordinary differential equations was obtained and the corresponding Cauchy problem was formulated, which is solved numerically using the Runge-Kutta method of the fourth order of accuracy.

On the basis of the proposed approach, numerical experiments were carried out to determine the roll-up time of the free-fall lifeboat, the speed of its center of masses, the angles of rotation and the angle of the tangage at the time of separation from the ramp at the value of the angle of inclination of the ramp and various values of the initial speed of the center of masses in the range from 1 to 10 m / s and the length of the hook in the range from 5 to 15 m.

According to the results of numerical experiments, an analysis of the effect of the initial speed and length of the FFLB on the parameters of its movement when descending from the inclined ramp was carried out. The estimated values of the time of the first phase of the fall, the angles of the tangage, the angular tangangle velocity and the module of the FFLB mass center velocity during the performed numerical experiments changed in the range of 1.424 - 0.234 s, 1.98 - 15.85 , 0.616 - 0.234 and 5,944-13,773 m/s, respectively. At the same time, with the increase in the length of the boat, the time of the first phase of the fall increases and decreases with an increase in the initial speed. The angles of the tangage decrease with increasing speed, and as the length of the boat increases, while the angular speeds of the tangage with an increase in the initial speed, as well as with an increase in the length of the b, fall off.

According to the results of the work, it was concluded that the proposed approach and numerical experiments could be used to rationally select the parameters of FFLB movement and the directions of further research.