Research on the Initial Ignition of the Underwater Launching Solid Rocket Motor

The aim of this investigation is to research the initial ignition of the underwater-launching solid rocket motor.The MIXTURE multiple-phase model was set to simulate the initial ignition.The water vaporization was researched and the energy transfer was added to the energy equations.The flow field and the vaporization were calculated coupled.The initial ignition process of the underwater solid rocket motor is obtained and the vaporization influence to the underwater launching is analyzed.The ＂neck＂,＂inverted jet＂ and ＂eruption＂ phenomenon of the bubble are observed.The bubble increases more rapidly because the steam mass added to the fuel.The temperature is lower considering the vaporization because the steam enthalpy is lower than the fuel enthalpy and the flow field of the initial ignition of the underwater-launching solid rocket motor is accordant well to the reference.

Numerical investigation of a muzzle multiphase flow field using two underwater launch methods

A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.

Transient interactions between bubbles and a high-speed cylinder in underwater launches: An experimental and numerical study

The underwater launch of high-speed vehicles involves complex bubble-structure interactions,which are not currently well understood.In this study,two small-scale experiments are carried out involving transient bubble-cylinder interactions.We adopt the underwater electric discharge method to generate a high-pressure bubble that drives a cylinder to a maximum velocity of∼25 m/s within 1 ms.A tail bubble forms as the cylinder is ejected from the launch tube.Moreover,we observe a shoulder cavity around the head of the cylinder due to the pressure reduction in the flow.To better understand the complex interaction between bubbles and the high-speed cylinder,we use the boundary element method to establish a bubble—structure interaction model.Our numerical model reproduces the experimental observations quite well,including the cylinder motion and the transient evolution of the bubbles.Thereafter,a systematic study is carried out to reveal the dependence of the bubble-cylinder interactions on the initial pressure of the tail bubble p0.We obtain a scaling law for the maximum velocity of the cylinder v_(m) with respect to p_(0),namely,v_(m) ∝ p_(0)^(0.45).The findings from this study may provide a reference for subsequent research into underwater launches.

Modeling tail bubble dynamics during the launch of an underwater vehicle using the boundary element method

A tail bubble is generated behind a high-speed vehicle at the early stage of the underwater launch process.The tail bubble dynamic behavior involves expansion,overexpansion,contraction,pinch-off and jet formation,and it significantly influences the vehicle’s movement.However,the tail bubble dynamic behavior is an issue not very well studied.This paper establishes a numerical model for the interaction between the tail bubble and the vehicle based on the boundary element method(BEM)to gain new insight into this issue.The BEM results are compared to a computational fluid dynamics model to validate the numerical model,and good agreement is achieved.Additionally,a convergence test of the BEM model is conducted to verify its independence of the mesh size.The influence of some governing parameters on the evolution of the tail bubble is then systematically studied,focusing on its maximum radius,pinch-off time,and pinch-off position.There are two pinch-off position regimes of the tail bubble,one at the bottom and the other near the middle.

Design and simulation of ex-range gliding wing of high altitude air-launched autonomous underwater vehicles based on SIMULINK

High altitude air-launched autonomous underwater vehicle （AL-AUV） is a new anti-submarine field, which is designed on the Lockheed Martin＇s high altitude anti-submarine warfare weapons concept （HAAWC） and conducts the basic aerodynamic feasibility in a series of wind tunnel trials. The AL-AUV is composed of a traditional torpedo-like AUV, an additional ex-range gliding wings unit and a descending parachute unit. In order to accurately and conveniently investigate the dynamic and static characteristic of high altitude AL-AUV, a simulation platform is established based on MATLAB/SIMULINK and an AUV 6DOF （Degree of Freedom） dynamic model. Executing the simulation platform for different wing＇s parameters and initial fixing angle, a set of AUV gliding data is generated. Analyzing the recorded simulation result, the velocity and pitch characteristics of AL-AUV deployed at varying wing areas and initial setting angle, the optimal wing area is selected for specific AUV model. Then the comparative simulations of AL-AUV with the selected wings are completed, which simulate the AUV gliding through idealized windless air environment and gliding with Dryden wind influence. The result indicates that the method of wing design and simulation with the simulation platform based on SIMULINK is accurately effective and suitable to be widely employed.

Modeling and Adaptive Sliding Mode Control of the Catastrophic Course of a High-speed Underwater Vehicle

Abstract： The mathematical model of a high-speed underwater vehicle getting catastrophe in the out-of-water course and a nonlinear sliding mode control with the adaptive backstepping approach for the catastrophic course are proposed. The speed change is large at the moment that the high-speed underwater vehicle launches out of the water to attack an air target. It causes motion parameter uncertainties and affects the precision attack ability. The trajectory angle dynamic characteristic is based on the description of the transformed state-coordinates, the nonlinear sliding mode control is designed to track a linear reference model. Furthermore, the adaptive backstepping control approach is utilized to improve the robustness against the unknown parameter uncertainties. With the proposed control of attitude tracking, the controlled navigational control system possesses the advantages of good transient performance and robustness to parametric uncertainties. These can be predicted and regulated through the design of a linear reference model that has the desired dynamic behavior for the trajectory of the high-speed underwater vehicle to attack its target. Finally, some digital simulation results show that the control system can be applied to a catastrophic course, and that it illustrates great robustness against system parameter uncertainties and external disturbances.