水下无人系统学报

Motion Control Simulation of Underwater Gliders in Kuroshio

MA Yuyin, WANG Yanfeng, GUAN Sheng, WANG Na, DING Junhang

2024, 32(1): 1-7. doi: 10.11993/j.issn.2096-3920.2023-0086

[Abstract](938) [FullText HTML] (20) [PDF 2036KB](42)

Abstract:
In recent years, underwater gliders have been widely used in the observation of various ocean surveys. However, their motion is often seriously affected when observing strong currents such as the Kuroshio. Therefore, the motion control of underwater gliders in the Kuroshio was studied in this paper. First, with Petrel-II as the research object, a dynamics model considering the Kuroshio was established based on the momentum and momentum moment theorem. Then, the Kuroshio data downloaded from the HYCOM website was used as interference, which featured varying speeds and directions of Kuroshio at different positions, and Simulink was used to simulate the motion of the Petrel-II under the influence of strong currents. Finally, the radial basis function(RBF) neural network was combined with the conventional proportional-integral-derivative(PID) controller to control the yaw motion and trim motion of the Petrel-II. The simulation results show that the RBF-PID controller can improve the motion tracking accuracy of Petrel-II in the Kuroshio area and enhance its ability to resist the interference of the Kuroshio. This study can provide a reference for the motion control of underwater gliders under the influence of strong currents to some extent.

Lightweight Modeling of Underwater Gliders and Nonlinear MPC Controller Design with Actuator Constraint

WANG Jieru, LI Chong, QI Shengbo, ZHAO Yuanyuan

2024, 32(1): 8-17. doi: 10.11993/j.issn.2096-3920.2023-0042

[Abstract](828) [FullText HTML] (14) [PDF 2482KB](41)

Abstract:
In response to the problems of high nonlinearity and dimensionality of existing underwater glider models, as well as difficulty in designing effective engineering controllers, the composition and working principle of the motion mechanism of underwater gliders were first studied. By neglecting secondary influencing factors in the modeling process, lightweight modeling of underwater gliders was conducted to reduce model nonlinearity and complexity. The effectiveness of the lightweight model was demonstrated through comparative verification. Subsequently, according to the motion in the vertical plane, the dynamic equation was further simplified, and the advantages of low dimension and small calculation amount of the model were brought into play. The actual constraints of state and control variables were introduced, and a realistic predictive attitude control algorithm for a real-time linearized model was designed. The numerical simulation results show that under the two common working conditions of ±17.4° and ±22.5° for underwater gliders, the control algorithm based on the lightweight model proposed in this paper can quickly track the desired attitude, and the rise time and steady-state settling time are improved by more than 70% compared with traditional controllers.

Real - Time Detection and Communication System for Underwater Acoustic Gliders and Their Offshore Experimental

TIAN Deyan, ZHANG Xiaochuan, ZHANG Wenqing, SUN Qindong, WANG Chao

2024, 32(1): 18-24. doi: 10.11993/j.issn.2096-3920.2023-0020

[Abstract](738) [FullText HTML] (9) [PDF 2555KB](44)

Abstract:
While performing underwater observation and detection, the underwater acoustic glider needs to finish the current profile glide to float to the surface for information exchange and thus fails to realize real-time data information return. In this paper, a detection and communication system for underwater acoustic gliders was proposed. The underwater acoustic communication technology was used to send the data information detected by the underwater acoustic glider to the wave glider. As a communication relay, the wave glider can transparently forward the data to the shore-based center, so as to realize the approximate real-time detection and communication data transmission. This paper introduced the structure, composition, and information transmission link of the detection and communication system for underwater acoustic gliders, emphatically discussed;the detection and communication test of underwater acoustic gliders in sea areas near Qingdao, and analyzed the test data. The test verifies the correctness and feasibility of the detection and communication system for underwater acoustic gliders and provides a reference for the subsequent application of Chinese underwater unmanned platform cluster cooperation and formation networking.

Research on Structural Principle and Hydrodynamic Performance of Double-Hull Hybrid Powered Underwater Glider

LIU Jian, ZHOU Guangli, PENG Jiashu, ZHU Meng, LI Guoqing, YU Zuyao

2024, 32(1): 25-31. doi: 10.11993/j.issn.2096-3920.2023-0150

[Abstract](663) [FullText HTML] (5) [PDF 1668KB](18)

Abstract:
Although the hybrid powered underwater glider has the advantages of both typical underwater gliders and traditional vehicles, it also has disadvantages such as high energy consumption and inconvenient recovery. In the rapid propulsion mode, the existence of wings not only increases navigation resistance and reduces navigation stability but also is not conducive to the recovery and deployment of gliders. In view of this, a dual-hull hybrid powered underwater glider was proposed. The wings of the glider can be retracted according to the actual needs, which is different from the traditional fixed horizontal wing, so as to realize the reasonable distribution of energy and improve the comprehensive navigation performance of underwater gliders. In addition, the working mode, system composition, and wing retracting principle of the glider were introduced in detail, and a worm gear and worm glide wings retracting device was designed. The corresponding retracting mechanism was established. On this basis, the hydrodynamic performance of the wings was analyzed by numerical simulation method, and a reasonable shipborne configuration scheme was obtained.

Pectoral Fin Structural Design and Experiments on Robotic Cow-Nosed Ray with Backward Swimming Performance

LI Bo, YU Yingming, CAO Yonghui, HAO Yiwei, PAN Guang, CAO Yong

2024, 32(1): 32-39. doi: 10.11993/j.issn.2096-3920.2023-0157

[Abstract](735) [FullText HTML] (24) [PDF 2615KB](30)

Abstract:
Robotic fish with pectoral fin swing have many outstanding features, especially forward swimming stability, but the research on their backward swimming performance is insufficient. Therefore, this article specifically discussed the hydrodynamic performance of the robotic cow-nosed ray with backward swimming in pectoral fin swing propulsion mode. Complete pectoral fin and split pectoral fin were designed, and the superiority of split pectoral fin structure over complete pectoral fin structure in terms of backward thrust was verified through experimental testing. The energy conversion efficiency was analyzed through the ratio of thrust to current. According to the collected current data, the equivalent thrust efficiency and amplitude and frequency variation curves of the two pectoral fin structures under forward and backward swimming conditions were drawn. The reasons for the thrust generation and equivalent thrust efficiency of two types of pectoral fin structures were analyzed. The experimental results show that under the forward swimming condition, the two types of pectoral fins have similar thrust values. Under the backward swimming condition, with the increase in amplitude and frequency, the thrust of the split pectoral fin structure increases significantly, reaching a maximum of 0.22 N. Under the forward swimming condition, the split pectoral fin structure is slightly worse than that of a complete pectoral fin. Under the backward swimming condition, with the increase in amplitude and frequency, the equivalent thrust efficiency of the split pectoral fin structure is significantly improved. The design of the split pectoral fin structure in the article provides a reference for exploring the backward swimming performance of robotic fish based on the swing mechanism.

Dynamic Modeling and Experimental Study of Biomimetic Robotic Manta Ray

CHEN Guojun, LIN Yanglong, JIN Jun, CHEN Wei, YANG Xue

2024, 32(1): 40-47. doi: 10.11993/j.issn.2096-3920.2023-0107

[Abstract](634) [FullText HTML] (7) [PDF 2111KB](14)

Abstract:
The unique pectoral fin swinging propulsion method of biomimetic robotic manta ray is more suitable for long-term underwater operations in wind and wave environments. Relevant research has been conducted both in China and abroad, but there are problems in the current research on biomimetic robotic manta ray, such as weak driving ability, low control accuracy, and poor biomimetic effects. This article took the natural manta ray as a biomimetic prototype, analyzed its biological characteristics and motion mechanism, and constructed its kinematics and dynamics models, thus providing a theoretical basis for the system design of the biomimetic robotic manta ray. The mechanical structure and control system were also designed. The experiments of straight forward swimming, in situ turning, and dynamic sinking and floating were carried out under simulated wave environments to test the performance of the biomimetic robotic manta ray in complex environments, verifying the motion performance and application prospect of biomimetic robotic manta ray.

Method for Maximum Power Control of Direct-drive Wave Power Device Based on Fuzzy Sliding Mode Control

FAN Xinyu, MENG Hao

2024, 32(1): 48-56. doi: 10.11993/j.issn.2096-3920.2023-0114

[Abstract](653) [FullText HTML] (11) [PDF 2856KB](13)

Abstract:
Marine wave energy is a new type of clean energy. In order to improve the generation power and wave energy conversion efficiency of the direct-drive wave power generation system, a maximum power control method based on fuzzy sliding mode control was proposed. The method aimed at solving the problems of large output ripple and poor system stability of the commonly used proportional-integral-derivative(PID) control method. In addition, the reaching law parameters were adjusted in real time according to the running state. At the same time, while realizing maximum power tracking, the output ripple was weakened; the tracking error was reduced, and the control quality of the system was improved. In this paper, the permanent magnet linear generator was used as the power generation device, and a system dynamics model was established. The main frequency of irregular waves was estimated by fast Fourier transform (FFT), and the expected current tracking curve was designed to meet the maximum power strategy. On this basis, the conventional PID and sliding mode control methods were compared with the proposed fuzzy sliding mode maximum power control method. The results show that the fuzzy sliding mode control method has improved power and shown better accuracy and stability.

An Improved MFAC Energy Saving Control Method for USVs in Wave Environments

WEI Jiaguang, ZHANG Tuosheng, XIN Yunwei, LI Huailiang, ZHANG Xiwei

2024, 32(1): 57-65. doi: 10.11993/j.issn.2096-3920.2023-0040

[Abstract](658) [FullText HTML] (3) [PDF 2259KB](14)

Abstract:
Unmanned surface vessels(USVs) are subjected to environmental disturbance in the process of movement. In particular, after being disturbed by waves, its motion control will deviate from the expected path, resulting in a waste of energy. In response to the problem of weak adaptability of fixed parameter controllers to the wave environment, the fuzzy control method was combined with the redefined model-free adaptive control(MFAC) method, and a fuzzy redefined MFAC(FRMFAC) algorithm was designed, which could adjust the control parameters according to the disturbance of different waves. At the same time, the line-of-sight method and FRMFAC algorithm were used to control the path following of USVs. Finally, compared with the fixed parameter control method, the effectiveness and energy saving effect of FRMFAC were verified. The simulation results show that the control method with variable parameters can effectively improve the adaptability of USVs to the environment and save energy.

Calculation Method of True Wind of Unmanned Sailboat Based on Data Fusion

HE Chenglong, CHI Shukai, YUWEN Guopu, HU Xinyao, WEI Pengfei, LI Ming

2024, 32(1): 66-78. doi: 10.11993/j.issn.2096-3920.2023-0017

[Abstract](766) [FullText HTML] (7) [PDF 2369KB](16)

Abstract:
Since the unmanned sailboat is difficult to obtain the true wind, and the wind sensor used is affected by the attitude of the sailboat, a calculation method of the true wind of the unmanned sailboat based on the fusion of attitude information, relative wind, and sailing wind was proposed. Firstly, the pitch angle and roll angle of the sailboat were obtained by using the attitude instrument, and the relative wind measurement results were corrected by the spatial coordinate rotation and transformation. Secondly, the Kalman filter algorithm was used to filter the sailing wind and the corrected relative wind. Finally, the extended Kalman filter was utilized to perform true wind fusion calculations. Experiments have proved that this method can effectively suppress the influence of sailboat motion on wind measurement, accurately extract true wind speed and wind direction, and ensure the sailing control of unmanned sailboats.

Research on Game Confrontation of Unmanned Surface Vehicles Swarm Based on Multi-Agent Deep Reinforcement Learning

YU Changdong, LIU Xinyang, CHEN Cong, LIU Dianyong, LIANG Xiao

2024, 32(1): 79-86. doi: 10.11993/j.issn.2096-3920.2023-0159

[Abstract](927) [FullText HTML] (42) [PDF 2328KB](72)

Abstract:
Based on the background of future modern maritime combats, a multi-agent deep reinforcement learning scheme was proposed to complete the cooperative round-up task in the swarm game confrontation of unmanned surface vehicles (USVs). First, based on different combat modes and application scenarios, a multi-agent deep deterministic policy gradient algorithm based on distributed execution was determined, and its principle was introduced. Second, specific combat scenario platforms were simulated, and multi-agent network models, reward function mechanisms, and training strategies were designed. The experimental results show that the method proposed in this article can effectively solve the problem of cooperative round-up decision-making facing USVs from the enemy, and it has high efficiency in different combat scenarios. This work provides theoretical and reference value for the research on intelligent decision-making of USVs in complicated combat scenarios in the future.

Comparison of Partial Admission Axial and Radial Inflow Turbines for Underwater S-CO₂ Power Cycle System

WANG Hanwei, JIANG Xiaopeng, LUO Kai, ZHANG Jianan, DANG Jianjun, QIN Kan

2024, 32(1): 87-96. doi: 10.11993/j.issn.2096-3920.2023-0037

[Abstract](42) [FullText HTML] (8) [PDF 3104KB](12)

Abstract:
The reasonable application of supercritical carbon dioxide(S-CO₂) power cycle systems to unmanned undersea vehicles(UUVs) can help address the problem of low efficiency for the existing UUV steam power cycle systems, especially for small-power applications. In order to select the optimal turbine for the underwater S-CO₂ system, the one-dimensional approach combined with the loss model was used to obtain the best geometric parameters within the design space. In addition, the three-dimensional numerical simulation method based on the RANS equation was adopted to verify the rationality of the one-dimensional design method. The aerodynamic performance and flow characteristics of the axial/radial turbine were further compared. The results show that the internal efficiency of the radial turbine is 5.41% higher than that of the axial turbine under the design conditions, but the size of the radial turbine is larger, about twice that of the axial turbine. The main loss of the radial turbine is from the nozzle and the rotor non-working section, while that of the axial turbine is mainly concentrated in the secondary flow losses generated at the rotor. Through the analysis of variable operating conditions, it is found that the axial turbine is more suitable for the low velocity ratio operating conditions. Nevertheless, the radial turbine has higher efficiency at the same speed. This research can provide a reference for the development of the S-CO₂ system power unit applied in UUVs.

Identity Authentication Method Based on Voiceprint Features of Communication Payloads

CHEN Lu, ZHAO Dexin, WANG Jun, GAO Hong, CHEN Yingliang

2024, 32(1): 97-104. doi: 10.11993/j.issn.2096-3920.2023-0027

[Abstract](49) [FullText HTML] (18) [PDF 1155KB](19)

Abstract:
The security of underwater acoustic communication networks is an important guarantee for information sharing and cooperative operation of underwater communication. Existing technologies mainly study authentication protocol and data encryption, focusing on improving the security of the network but ignoring the efficiency and energy consumption of the network. To avoid network congestion caused by the above methods, this paper, inspired by research in mobile smart devices and other fields, proposed to integrate voiceprint authentication into the identity authentication system of underwater communication networks, and it designed a recognition method based on voiceprint features of communication payloads. This method used the attention mechanism and merged nonlinear cepstrum features and phase spectrum features to reduce the influence of complex marine environment noise. In addition, it identified the target through the AlexNet network. To verify the effectiveness of this method, this paper collected underwater acoustic communication signals, verified the difference and effectiveness of the proposed voiceprint feature recognition, and demonstrated the feasibility and reliability of the proposed method. The research in the paper provides a new idea for solving the identity authentication of underwater acoustic communication networks, which serves as a reference for enhancing security and realizing high-quality information sharing and high-efficiency cooperative control of underwater acoustic communication networks.

Quantitative Analysis of Uncertainty at the End of the Towed Cable in Underwater Towing Systems

CHENG Shunzhao, WANG Jun, LIANG Xiaofeng, WANG Jian

2024, 32(1): 105-113. doi: 10.11993/j.issn.2096-3920.2023-0085

[Abstract](30) [FullText HTML] (5) [PDF 1336KB](9)

Abstract:
In the ever-changing marine environment, the key to the optimal design of the towed cable and the precise control of the towed body in the underwater towing system is the quantification of uncertainty at the end of the towed cable. The Monte Carlo(MC) method, a traditional uncertainty quantification method, has high computation costs and low accuracy. In view of this, a method of uncertainty quantization at the end of a towed cable based on polynomial chaos(PC) was proposed. Latin hypercube sampling was used to obtain sample sets of the towed cable parameters, and the sample sets were substituted into the lumped-mass method model to obtain the coordinate of the end position of the towed cable. A proxy model of the end response of the towed cable was generated by the PC method, and the uncertainty of the end was quantified according to the characteristics of the orthogonal polynomials. At the same time, the results of the PC method were compared with those of the MC method. The results show that compared with the MC method, the PC method has a faster convergence speed in terms of sample size and higher accuracy. The uncertainty of motion response is approximately proportional to the axial length of the towed cable; the increase in cable length leads to the increase in uncertainty at the end, and the increasing trend is gradually flattened. When the uncertainty of the towed cable parameters is constant, increasing the speed of the mother ship helps to improve the stability of the towed body at height. The accuracy and efficiency of the PC method have been verified. Meanwhile, the quantitative analysis results of the uncertainty at the end of the towed cable guide engineering problems.

Hydrodynamic Performance of Efficiency Transition Point of Forked Caudal Fins

XIONG Zhongying, LIU Yueyao

2024, 32(1): 114-123. doi: 10.11993/j.issn.2096-3920.2023-0066

[Abstract](30) [FullText HTML] (4) [PDF 3028KB](10)

Abstract:
Thunniform fish has high swimming speed and swimming efficiency and thus becomes the ideal biological prototype of bionic robotic fish. In order to study the hydrodynamic characteristics of the efficiency transition point of the forked caudal fins of thunniform fish, the source terms influencing thrust and power consumption were mainly analyzed. The caudal fin model used the same surface area, aspect ratio, and fork length. To unify the metrics about the fin shape, the sweep angle was used to represent the structure for the forked caudal fins in this paper. It is found that the increase in the sweep angle attenuates the available area of the caudal fin of the thunniform fish, resulting in a lower reaction force to push the fluid downstream when the caudal fin swings. As a result, the thrust of the caudal fin decreases. Additionally, the rise in the sweep angle also triggers the enhancement of the strength and the development of the leading-edge vortex, thereby inducing greater vortex-augmented thrusts. However, an excessive increase in the sweep angle may trigger a decline in the thrust and efficiency, especially for a high Strouhal number, along with a decrease in power consumption. It is found that the sweep angle has an opposite action on the added mass force and vortex-augmented thrust by analyzing the source term of thrust.

Implementation and Application of Bellhop Model in Underwater Acoustic Network Simulation

LIU Qipei, LIU Kun, LUO Yihao, WU Xinying, ZHOU Heyu

2024, 32(1): 124-129. doi: 10.11993/j.issn.2096-3920.2023-0015

[Abstract](58) [FullText HTML] (19) [PDF 1424KB](26)

Abstract:
With the development of underwater acoustic technology, underwater acoustic networks(UANs) have attracted much attention due to their performance in marine surveillance, disaster warning, and ocean security. The underwater acoustic channel is a crucial factor affecting the performance of UANs, and its complexity directly affects the pre-design and evaluation of UAN-related protocols, which is crucial to the practical application of protocols. Unlike traditional theoretical models, the Bellhop underwater acoustic channel model provides a more accurate method to obtain channel characteristics under different oceanic environments by calculating their acoustic fields via ray tracing. However, it cannot be directly applied to network simulation. This paper implemented a Bellhop underwater acoustic channel model based on NS3, the current most popular network simulation platform, and applied the Gaussian ray model to UAN simulation. The comparison results show that the model can effectively simulate the underwater propagation characteristics of acoustic signals and provide a reference for practical UAN-related protocol development.

Design Method for Low Specific Speed Axial Flow Pump for High-Speed Undersea Vehicles

ZHANG Ziruo, LUO Kai, QIN Kan

2024, 32(1): 130-138. doi: 10.11993/j.issn.2096-3920.2023-0036

[Abstract](40) [FullText HTML] (13) [PDF 1988KB](13)

Abstract:
For the axial flow pumps water-jet propulsion system of undersea vehicles, the high specific speed axial flow pump designed by the lift method fails to work under shallow water and high-speed conditions at present. Therefore, this study put forward a method to design a low specific speed axial flow pump. By considering the blade grid characteristics of the NACA66_a=0.8 airfoil, the design relationship among the angle of attack, lift coefficient, and other parameters was changed to establish an axial flow pump model suitable for high-speed conditions, and SST k-ω turbulence model and multi-reference frame model were used to simulate the flow field motion of the designed pump. The results show that under the design conditions, for the head and hydraulic efficiency of the designed pump, the error between the design value and the emulation value is controlled within 8%. At the same time, the cavitation resistance of the designed pump at different depths is tested to explore the minimum depth where the designed pump can work.

Influence of Amplitude-phase Error on MVDR Beamforming of Volume Array

HUANG Yan, JIAO Junsheng, GUO Shixu, ZHAO Peng

2024, 32(1): 139-146. doi: 10.11993/j.issn.2096-3920.2023-0077

[Abstract](30) [FullText HTML] (7) [PDF 1520KB](6)

Abstract:
Volume array is a kind of three-dimensional array composed of multiple hydrophones, which can increase the aperture of the receiving array of the submarine target and obtain a large spatial gain. In engineering, it is often made into an array with the function of folding and expanding for dropping sonar at low frequency. Because the parameters and amplitude gain of the devices in each hydrophone channel are inconsistent, there are amplitude-phase errors between the signals received by each element of the volume array. In this study, a double-ring volume array model with amplitude-phase errors was established, and the effects of the amplitude-phase errors on the covariance matrix, as well as the output signal-to-noise ratio(SNR), array gain, and azimuth estimation accuracy of the minimum variance distortionless response(MVDR) beamformers, were statistically analyzed. The computer simulation results show that the existence of array amplitude-phase error will reduce the output SNR and array gain of MVDR beamformers. For phase error, when the input SNR is above −5 dB, the effect becomes more and more obvious with the increase in the input SNR. As for the amplitude error, when the input SNR is above −10 dB, the amplitude error has a more significant effect on the output SNR and array gain of MVDR beamformers. Moreover, the azimuth estimation accuracy of MVDR beamforming is more sensitive to the phase error than the amplitude error.

Simulation Analysis of Variable Cross-section Linetype Optimization for Swim-out Tube in UUVs

ZHOU Jie, MA Liang, HENG Hui

2024, 32(1): 147-151. doi: 10.11993/j.issn.2096-3920.2023-0089

[Abstract](14) [FullText HTML] (1) [PDF 1117KB](9)

Abstract:
In order to design the swim-out launcher unit for unmanned undersea vehicle(UUV), based on the thrust model and force model of swim-out launch process for electric torpedoes, the paper analyzes the thrust, fluid resistance, course resistance, and local resistance suffered by the torpedo during its swim-out launch process, establish a mathematical model for torpedo swim-out launch, and establish a simulation program to calculate the tube-exit velocity. Taking the launching speed as a key indicator, the linetype of variable cross-section swim-out tube is optimized. Determine the length and diameter of each section of the launch tube as constraints, and then build the mathematical expression of the optimization problem. To accelerate convergence, a genetic algorithm with adaptive mutation probability is used for optimizing the linetype of the tube, and 100 generations of simulation calculations are conducted. Compare the launching speed to obtain the optimization result. Based on the results, the optimal linetype of swim-out tubes is drawn. This result is a beneficial attempt to explore the variable cross-section launch technology of UUV and provides a theoretical basis for the design of the variable cross-section swim-out tube.

Analysis of Multi-Body Separation Characteristics of Trans-Medium Vehicles

WANG Shuai, DONG Meng, WANG Sheng

2024, 32(1): 152-157. doi: 10.11993/j.issn.2096-3920.2023-0022

[Abstract](44) [FullText HTML] (5) [PDF 1745KB](15)

Abstract:
This paper studied the underwater separation characteristics of pods of trans-medium vehicles by numerical simulations of computational fluid dynamics and dynamics model simulations and analyzed the hydrodynamic forces exerted on the pods before and after separation. The analysis results show that 1) with appropriate shapes, the pods can separate from the vehicle under the action of hydrodynamic forces; 2) the opening angle and opening angular velocity of the pods have a large impact on the hydrodynamic forces. At different opening angles, the generation mechanisms of the separation moment are different. At a small opening angle, the opening of the pods mainly relies on the internal and external pressure difference generated by the low pressure in the outer separation zone, and the fluid moment is mainly generated by the front section of the pods. At a large opening angle, the opening of the pods mainly relies on the normal force caused by water flow impact, and the moment is mainly generated by the middle and rear sections of the pods; 3) the damping moment of the fluid is large when the opening angle of the pods is small, which makes it hard for the pods to separate from the vehicle quickly at the initial stage. As the opening angle increases, the damping moment of the fluid gradually decreases, and the opening angular velocity of the pods rapidly increases. Therefore, appropriate shapes and separation methods should be designed to reduce the initial damping moment of the fluid of the pods during underwater separation.

Numerical Simulation Accuracy Study of Underwater Explosion Shock Waves

AO Qiyuan, LU Xi, JIANG Zhiya, KANG Poge

2024, 32(1): 158-165. doi: 10.11993/j.issn.2096-3920.2023-0098

[Abstract](38) [FullText HTML] (16) [PDF 1606KB](6)

Abstract:
In the numerical simulation study of the underwater explosion, the grid size and the artificial viscosity coefficient of the primary term have a large impact on the calculation results of the peak pressure of the shock wave. Under the condition of predetermined calculation accuracy, it is of great significance to quickly determine the grid size and artificial viscosity for numerical calculation. For this reason, based on LS-DYNA finite element software, a two-dimensional underwater explosion numerical calculation model of 78 g trinitrotoluene (TNT) was established to analyze the influence of the grid size and the viscosity coefficient of the primary term on the peak pressure of the underwater explosion shock wave and the overall calculation error. The results show that with the increase in the grid density factor, the sensitivity of calculated peak pressure to the grid decreases. When the grid density is larger, a small primary term coefficient will cause the relative error between the calculated peak pressure and the empirical formula value to increase. On this basis, the relationship among the error, grid size, and viscosity coefficient within 20% is obtained, and an error prediction model that can be used to quickly determine the grid size and the artificial viscosity coefficient of the primary term is constructed. Through the underwater explosion calculation of cylindrical TNT charge (aspect ratio of 1) and spherical TNTcharge in the range of 0.2–5 000 kg, the universality of the prediction model is verified, which can provide a reference for the numerical simulation of underwater explosion shock wave in the two-dimensional near-field range.

Application of Reliability Simulation in Torpedo Products

WANG Douhui, CHEN Huan, GUO Jun, WU Bin

2024, 32(1): 166-173. doi: 10.11993/j.issn.2096-3920.2023-0030

[Abstract](31) [FullText HTML] (4) [PDF 15347KB](18)

Abstract:
The traditional reliability test is time-consuming and requires high cost. Therefore, this article provided the basic content and workflow of reliability simulation and conducted reliability simulation modeling, thermal stress simulation analysis, vibration stress simulation analysis, fault prediction, and reliability evaluation for typical electronic components in a certain torpedo product, so as to obtain weak links in product design, potential fault information, and average first failure time. The analysis results show that the reliability simulation can ensure the elimination of fault sources in the early stage of torpedo product design and thus improve torpedo product robustness and fault prediction ability.

Application Status and Development Trend of Battery for Deep Submergence Rescue Vehicles

HE Weiwei, ZHANG Wei, XIE Fei, MA Ling, CHENG Fei

2024, 32(1): 174-182. doi: 10.11993/j.issn.2096-3920.2023-0052

[Abstract](41) [FullText HTML] (7) [PDF 8688KB](16)

Abstract:
Submarines have extremely strong operational capability and deterrence and play an irreplaceable role in war, which have been highly valued by all countries. However, the operational characteristics of submarines also reflect that once an accident occurs, rescue will be difficult. Among various types of rescue equipment, deep submergence rescue vehicle (DSRV) have the advantages of flexible operation and a large number of rescuers, which is an efficient rescue technology. Therefore, the navies of various countries have developed multiple types of DSRVs for submarine crash rescue. DSRVs mainly rely on the battery to provide energy under water. Therefore, the performance of the battery also determines that of the DSRV to a certain extent. This paper mainly reviewed the application status of batteries for various types of DSRVs worldwide, analyzed the current application status, key technologies, and research foundations of battery technology for DSRVs, and predicted future development trends of battery technology applied for DSRVs, so as to provide a reference for the development of batteries for DSRVs in the future.

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Current Issue
2024, Volume 32, Issue 1