Cooperative Sampling Path Planning of Underwater Glider Fleet with Simultaneous Launch and Recovery

As low-cost and highly autonomous ocean observation platforms,underwater gliders encounter risks during their launch and recovery,especially when coordinating multi-glider deployments.This work focuses on cooperative path planning of an underwater glider fleet with simultaneous launch and recovery to enhance the autonomy of sampling and reduce deployment risks.Specifically,the gliders collaborate to achieve sampling considering the specified routines of interest.The overall paths to be planned are divided into four rectangular parts with the same starting point,and each glider is assigned a local sampling route.A clipped-oriented line-of-sight algorithm is proposed to ensure the coverage of the desired edges.The pitch angle of the glider is selected as the optimizing parameter to coordinate the overall progress considering the susceptibility of gliders to currents and the randomness of paths produced by complex navigational strategies.Therefore,a multi-actuation deep-Q network algorithm is proposed to ensure simultaneous launch and recovery.Simulation results demonstrate the acceptable effectiveness of the proposed method.

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.

Wave Influence on Underwater Launch and Recovery System

In this paper, the underwater vehicle, sling and the mother ship are considered as a single degree of freedom system connected by a spring. Through the analysis of this system, a physical model is established, which describes the motion of the vehicle caused by the ship motion and wave motion. Furthermore, a mathematical model based on this physical model is obtained, and a numerical solution program is made. As an example, a practical launch and recovery system fbr an underwater robot is calculated by use of the program, and the motion track of the robot is obtained.

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.

The Hydrodynamic Computation on Moving Base Vertical Launching of an Underwater Missile

In order to study the effects of lateral flow on the underwater missile vertical launching process considering the hydrodynamic effect, a horizontal fluid dynamics model was developed. We offered the numerical computation method in this process by using the fluent of CFD （ Computational Fluid Dynamics）software. Based on the specific examples, we carried out the computation of the model＇s drag coefficient, lift coefficient and pitching moment with its launching process. The computation results agree with the results of the experiment and the error between them is less than 10%. It shows that this computation method is viable and can be used in the system design, and the analysis of missile motion and basic structure intensity.

Underwater Explosion Technology for Offshore Engineering Applications

- This article briefs how to improve the holding power of a drilling vessel's anchor and to remove those unreasonable structures by such a technology - underwater-explosion technology. The article gives details of the structure, characteristics and applications of a rocket-launched anchor; as well as the principle, properties, applications of directional explosion cutting.

水下连续发射弹体干扰特性及发射时序优化

随着对饱和攻击需求的提高,潜艇连续发射过程的发射时序协调控制研究变得迫切而紧要。考虑到弹体间的流体动力干扰是影响安全发射的主要因素,基于重叠网格多自由度仿真技术,针对连续发射的水下弹体开展姿态弹道干扰特性研究。通过分析流场结构发现,以一定攻角发射的弹体形成的发卡形尾涡是造成后续弹体姿态弹道差异的主要原因。根据不同艇速、时间间隔和空间间隔下弹体间的干扰特性建立干扰评价模型。在保证干扰不影响后续弹体的前提下,以最短发射时长为目标,以综合评价函数为约束,基于改进的贪心算法对大筒多弹式布局的水下弹体开展发射时序优化研究,并采用均匀抽样方法验证优化结果准确性。研究结果表明:相对于均匀抽样方法,改进的贪心算法具有相当的计算准确度和更高的计算效率。

自主水下机器人布放回收技术综述

对水下机器人布放回收这一领域的研究进行了综述并对未来研究进行了展望。首先分析了水下机器人布放回收的不同方式,主要可分为水面有人舰船、水面无人船、潜艇以及大型水下机器人布放回收方式。接着举出不同回收方式的国内外例证并对其优缺点进行总结。随后探讨和分析了实现布放回收所需的关键技术,包括自主对接技术、定位引导技术、锁紧定位技术及对接回收策略,并对技术现状及装备进行举例分析。最后对水下机器人布放回收的研究方向和重点进行了展望。综述表明,水下机器人布放回收的结构和所需关键技术还需持续研究,特别需要关注的是随着布放回收技术研究的不断深入,未来水下机器人布放回收系统将向自主化、无人化、通用化发展。

水压驱动两级提拉式水下发射装置内弹道建模

针对大深度环境水下发射技术需求,提出一种利用水压驱动两级提拉式水下新型发射方案。利用大深度环境高压水驱动两级活塞实现武器快速发射。建立武器出管过程动力学模型,开展高压水驱动方案原理验证试验,并与高压气体驱动方案进行了对比分析。研究结果表明:水压驱动与气体驱动方案的内弹道结果基本一致,高压水发射方案在大深度环境具有显著优势;加速度峰值出现在发射瞬时和级间转换过程,级间转换过程武器加速度存在显著的陡变现象;水下发射武器出管过程弹道预报结果得出,在发射水深100~500 m条件下,武器出管过程最大速度范围为7.4~15.3 m/s,最大加速度小于100 m/s 2;研究结果验证了水压驱动两级活塞式发射方案的可行性,为装置的进一步研制开发提供了设计依据。

水下运载器动力学仿真以及串级控制器参数优化

为了让水下运载器能够更好完成潜射无人机的跨介质机动,基于回转体结构以及ROV(Remote Operated Vehicle)驱动模式设计一种具有动力的潜射无人机水下运载器。根据该运载器的外形结构和驱动模式特点,对其进行动力学建模并设计一种串级控制器控制该运载器的六自由度运动参数,利用Matlab/Simulink进行仿真验证,最后利用Isight优化软件对该运载器的串级控制器参数进行优化,分别利用自适应DOE优化算法和Evol优化算法进行优化计算,经过优化后的串级控制器在六自由度上的轨迹跟踪效果均有提升,其中Evol优化算法优化效果更好,计算成本更小。

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.

冲击载荷作用下航行体典型部段结构力学分析

对于航行体水下垂向破冰过程,航行体典型部段受荷载特征存在很大不确定性。因此,基于ALE流固耦合算法,运用LS-DYNA软件对航行体部段壳体厚度、材料屈服强度两个参数下部段的力学响应进行了求解分析。结果表明:航行体Ⅰ-Ⅱ级部段在破冰过程中所受应力大于Ⅱ-Ⅲ级所受应力,这与部段后端相连部段的惯性力有关;部段的t/D(壳体厚度与航行体外径之比)由0.009增加至0.012,Ⅱ-Ⅲ级部段应力由362.9 MPa下降至323.4 MPa,Ⅰ-Ⅱ级部段应力由326.4 MPa下降至222.3 MPa,Ⅱ-Ⅲ级部段应力下降趋势较Ⅰ-Ⅱ级部段更加明显;使用钛合金材料的两个部段结构强度均满足设计要求,使用碳纤维材料的Ⅰ-Ⅱ级、Ⅱ-Ⅲ级部段所受应力分别超过了其许用应力7.4%、21.2%,使用镁合金材料的Ⅰ-Ⅱ级应力超过材料屈服极限29.7%、Ⅱ-Ⅲ级超过屈服极限3.2%。

航行体水下连续发射尾涡遭遇与运动干扰特性

为研究不同发射时间间隔下航行体水下连续发射尾涡干扰与弹道特性,基于Realizable k-ε湍流模型和能量方程、流体体积方法和重叠网格技术,开展数值方法和网格无关性验证,数值模拟结果与实验测试结果吻合度较好。建立航行体水下连续发射数值模拟方法,研究航行体尾流区涡结构的演变机理、次发航行体表面压力分布、弹道以及俯仰姿态演变规律。研究结果表明:航行体水下连续发射过程中在其尾流中发现了发卡涡形态的流动结构,该涡结构由涡头与两条涡腿组成,通常以多个共同组合的形式存在于航行体尾部的流场区域中;沿涡腿内侧发生喷射事件,沿涡腿外侧发生扫掠事件,同时在涡结构内部形成一定流向尺度的低速条带区域;在横流效应下,当次发航行体表面穿过尾流中涡结构中的低速条带区时,迎背流面压力分布特性得到较大的改善,增加了弹道姿态稳定性。

基于USV的AUV布放回收系统设计与实现

为了解决目前布放回收自主水下机器人(autonomous underwater vehicle,AUV)自动化水平低、工作效率低、危险性高等问题,研制了一款基于无人水面船(unmanned surface vessel,USV)的AUV自主布放回收系统。首先,通过分析国内外常用AUV布放回收方式和布放回收系统,设计了AUV布放回收系统,并对其工作原理进行分析;其次,分别从力学分析、数值仿真等角度研究了布放回收系统的动力学、静力学及接触碰撞问题;最后,搭建了系统原理样机并进行了陆上实验和湖上实验,通过实验验证了所设计的布放回收系统稳定可靠、操作简单、通用性好,可以有效提高AUV自主布放回收的效率。所设计的基于USV的AUV布放回收系统具有良好的应用前景。

筒口气团作用下航行体垂直出筒数值研究

潜射航行体出筒过程是水下发射的基础与前提,具有受力剧烈、时间短和非线性等特点。基于CFD方法,利用VOF多相流模型追踪气液界面,结合高分辨率交界面捕捉(HRIC)与重叠网格(零间隙)技术,建立了完整描述航行体水下垂直出筒的数学模型,系统研究了筒口气团与发射参数对流场与航行体载荷特性的影响规律。结果表明:随着筒口气团初始压强的增加,航行体受力变化周期增长,筒口气团演化过程减慢;发射深度的增加有助于缩短出筒过程中筒口气团脉动周期,肩部压强增加,有利于抑制航行体自然空化;横向来流会显著增加航行体横向受力与偏转力矩;横向流作用下,筒口气团脉动过程对航行体偏转力矩与横向受力影响较大。

航行体水下高膛压与高速发射载荷特性

水下高膛压高速发射航行体后形成的多相流场复杂多变,产生的载荷影响尚未明确。针对某小口径水下航行体高膛压、高初速冷发射过程,开展发射载荷特性研究,分析航行体发射过程中内弹道阶段、溢出燃气与水相互作用阶段、水锤效应阶段的流场特性与力学特点。基于多相流模型和动网格方法,建立航行体水下高速冷发射过程数值模型,进行气-汽-液多组分数值仿真,对不同时期发射筒的载荷特性及其成因进行分析。研究结果表明:水下航行体高速发射载荷主要来源于内弹道过程与水锤效应,航行体出膛后筒内燃气溢出造成的低压区产生载荷较小;与低膛压、低初速发射工况不同,高膛压发射工况下筒内气体高速大量溢出,水锤效应压力峰值的幅度衰减明显。

无人机水下发射试验系统弹射性能的仿真研究

为研究无人机水下发射的可行性及其弹射过程动力学性能,对系统主要参数进行影响规律和灵敏度分析。通过研究机械结构和传动系统的耦合特性,建立基于AMESim和ADAMS的水下发射试验系统动力学联合仿真模型,在发射角10°~90°范围内对3种类型无人机进行仿真,得到发射速度随发射角和储气瓶压力的变化规律;利用局部灵敏度分析方法,对储气瓶压力、储气瓶容积、气缸有效面积和行程4个关键参数进行了影响发射速度和加速时间的规律分析。结果表明:在相同压力下,随着发射角的增大和无人机模型质量的减小,其脱离发射架的速度逐渐增大;影响发射速度灵敏度最大的参数为储气瓶压力,随着压力的增大,速度增大的幅度逐渐减小;影响加速过程时间灵敏度最大的参数为储气瓶压力和气缸有效面积。

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.

A COUPLING MODEL OF WATER FLOWS AND GAS FLOWS IN EXHAUSTED GAS BUBBLE ON MISSILE LAUNCHED UNDERWATER

The gas and water flows during an underwater missile launch are numerically studied. For the gas flow, the explicit difference scheme of Non-oscillation and Non-free-parameter Dissipation (NND) is utilized to solve the Euler equations for compressible fluids in the body-fitted coordinates. For the water flow, the Hess-Smith method is employed to solve the Laplace equation for the velocity potential of irrotational water flows based on the potential theory and the boundary element method. The hybrid Eulerian-Lagrangian formulation for the free boundary conditions is used to compute the changes of the free surface of the exhausted gas bubble in time stepping. On the free surface of the exhausted gas bubble, the matched conditions of both the normal velocities and pressures are satisfied. From the numerical simulation, it is found that the exhausted gas bubble grows more rapidly in the axial direction than in the radial direction and the bubble will shrink at its "neck" finally. Numerical results of the movement of the shock wave and the distribution of the Mach number and the gas pressure within the bubble were presented, which reveals that at some time, the gas flow in the Laval nozzle is subsonic and the gas pressure in the nozzle is very high. Influences of various initial missile velocities and chamber total pressures and water depths on both the time interval when the gas flow in the nozzle is subsonic and the peak of the gas pressure at the nozzle end were discussed. It was suggested that a reasonable adjustment of the chamber total pressure can improve the performance of the engine during the underwater launch of missiles.