Analysis of Motion Characteristics of a Controllable Ventilated Supercavitating Vehicle Under Accelerations

Abstract

The development of a maneuverable underwater high-speed vehicle is worthy of attention and study using supercavitation drag reduction theory and technology. The supercavity shape determines the hydrodynamics of the vehicle, and especially during a maneuver, its unsteady characteristics have a significant impact on the motion stability of the vehicle. The three-dimensional dynamic model of a ventilated supercavitating vehicle is established using the unsteady supercavity dynamic model based on the rigid body dynamics theory as an extension of the vehicle's longitudinal dynamic model in our recent work. The vehicle's accelerating and decelerating motions are simulated in the straight flight state using a self-developed numerical method based on the vehicle's dynamic model with the designed control law. Motion characteristics are analyzed on the evolution laws of the vehicle's motion state variables and control variables and the supercavity's characteristic parameters (i.e., ventilation cavitation number, supercavity maximum diameter and supercavity length) in the acceleration motions. The evolution laws in the accelerating and decelerating motions are compared, and the effects of the acceleration on the laws are further analyzed. This study lays the foundation for the in-depth study of the hydrodynamic characteristics and motion stability of ventilated supercavitating vehicles in maneuvering states.

Free motion characteristics of the ventilated supercavitating vehicles

“…Supercavity deforms under gravity and the cavitator's lateral force. Based on the conservation of momentum theorem, the supercavity longitudinal axis shifts caused by these two factors are formulated in Equation ( 3), where the variables and parameters are explained in our work [8].…”

“…Due to the changes in the motion parameters of the SCAV, the supercavitating flow is unsteady. Therefore, the internal gas mass conservation is considered in the following [8].…”

“…Based on the body coordinate system set at cavitator, the SCAV's dynamic model is established. Its mathematical form in the longitudinal plane is written in Equations ( 6)-( 8), where motion variables and forces are detailed in [8].…”

“…This study applies the SL model to effectively close the supercavity dynamic model equations, thereby improving the SCAV dynamic model [8]. Based on the dynamic model, level-free motions of the ventilated SCAV are simulated to analyze motion and hydrodynamic distribution characteristics, in which internal pressure is maintained constant under ventilation control.…”

Experimental and numerical study on unsteady entrainment behaviour of ventilated air mass in underwater vehicles

“…Many years ago, researchers carried out a series of scientific investigations into the motion characteristics of bubbles in liquids (Bhaga and Weber 1981, Logvinovitch 1969, Clift et al 1978, Coutanceau and Thizon 1981, Lauer et al 2012, and determined the dynamic behaviour of bubbles in different viscous liquids. Through further research, it was found that the ventilated cavity covering the surface of an underwater vehicle can effectively reduce the travelling resistance (Jiang et al 2019, Zou et al 2021, which provides a new direction of research into underwater vehicles. Kim and Kim (2015) further studied the hydrodynamic characteristics of ventilated supercavities and established a dynamic model for vehicles that produced this phenomenon.…”