To study the motion characteristics of moving bodies in the course of high-speed water entry in parallel

and to predict the mutual influence trends between moving bodies

combined with the results of numerical simulations

the prediction formulas for the lateral and yaw motions of the moving body were derived

and strategies to avoid instability were proposed. Firstly

the validity of the numerical calculation method was verified

and based on the numerical calculation results

a restrictive hypothesis about jerk was put forward

so as to obtain the prediction formula for the lateral displacement and yaw angle of parallel water-entry revolution bodies. Secondly

the effects of initial cavitation number and initial clearance distance on lateral and yaw motion characteristics were studied through the prediction formula. Finally

based on the concept of kinematic factor

the kinematics of collision and excessive distance was studied

and a strategy to avoid the instability of revolution bodies was proposed. Results show that the prediction formula was in good agreement with the numerical calculation results. When the initial cavitation number was small

the head pressure promoted lateral and yaw movements

and the smaller the initial cavitation number was

the greater the nominal lateral jerk and yaw angle were

indicating that the lateral and yaw motions were promoted more strongly. When the initial clearance distance was small

the inner pressure inhibited the lateral and yaw movements

and the smaller the initial clearance distance was

the larger the lateral correction factor and the yaw angle correction factor were

indicating that the lateral and yaw motions were inhibited more strongly. The initial conditions and the shape of the revolution body together determine the state of the revolution body. The initial speed of water entering and the initial clearance distance should be controlled within a reasonable range to avoid motion instability.