水下无人系统学报

Simulation on Impact Load and Cavity Shape in High Speed Vertical Water Entry for an Axisymmetric Body

QIU Hai-qiang, YUAN Xu-long, WANG Ya-dong, LIU Chuan-long

2013, 21(3): 161-164. doi: 10.11993/j.issn.1673-1948.2013.03.001

[Abstract](1229) [PDF 207KB](567)

Abstract:
The problem of high-speed water entry of an axisymmetric body greatly influences the design of shape and trajectory for a torpedo or a missile. This paper simulates the impact and cavity shape in water entry of different head shapes, such as flat head, cone head, and round head, at the velocity between 50 ~150 m/s with the commercial software FLUENT6.3 combining with the dynamic mesh, user-define function(UDF) and MIXTURE model. Conclusions are drawn that the peak of impact load appears in the primary period of the water entry; the impact load and the cavity′s length and diameter increase with the increasing velocity; while the impact load and the cavity′s length and diameter decrease in the order of flat head, cone head, and round head when the bodies have same velocity.

Numerical Simulation Method for Ventilated Supercavitating Multiphase Flow Field

ZHOU Jing-jun, DONG Chun-peng, YIN Shao-ping, XIANG Qing-rui

2013, 21(3): 165-171. doi: 10.11993/j.issn.1673-1948.2013.03.002

[Abstract](1104) [PDF 365KB](680)

Abstract:
Ventilated supercavitating flow involves such topics in fluid mechanics as multiphase flow, turbulence, phase change and compressibility, its mechanism is very complex. The multiphase flow model has attracted much more atten-tion in the study of numerical simulation of supercavitating flow, however its accuracy in simulation is not satisfactory. In this paper, the homogeneous model, which are widely used in the world, are compared with the Euler two-fluid model by combining with the authors′ research by means of water tunnel experiments and numerical simulation. The advan-tages of the Euler two-fluid model in predicting ventilated supercavitation is analyzed in terms of cavity shape and hy-drodynamics of a vehicle. Numerical simulation of ventilated supercavitation is expected to become an important ap-proach of drag-reduction technology through supercavitation.

Modeling and Simulation of Multi-body Dynamic for Rocket-Assisted Torpedo Separation

BAI Zhao-gao, WANG Feng-hui, WEN Zhen

2013, 21(3): 171-174. doi: 10.11993/j.issn.1673-1948.2013.03.003

[Abstract](899) [PDF 233KB](555)

Abstract:
This paper analyzes the structure and force of the multi-rigid-body system composed of vehicle and separating cabin, establishes a Lagrange equation of multi-body dynamic model, and then simulates the motion state of the com-bined system in a given initial condition by fourth-order Runge-Kutta method. The multi-body dynamic models are veri-fied by comparing the simulation results with the test ones. This study may provide a basis for safety analysis of the separation process of rocket-assisted torpedo.

A Bayesian Reliability Evaluation Method Based on Dempster-Shafer Evidence Theory

ZHAO Fang-ze

2013, 21(3): 175-178. doi: 10.11993/j.issn.1673-1948.2013.03.004

[Abstract](1308) [PDF 209KB](571)

Abstract:
Bayesian method is an important and suitable approach for system reliability evaluation in small sample cir-cumstance. In order to reduce the testing data, all kinds of a priori information must be used, so the information fusion of multiple sources becomes a key problem in Bayesian analysis. A new method based on the Dempster-Shafer evidence theory is proposed to realize the information fusion of multiple sources, which can integrate more a priori distributions obtained through different fusion criteria. Simulation shows that the proposed method is effective.

A Simulation Method of Shallow Water Reverberation Based on K-distribution Model and Multipath

GENG Yun-hui, FENG Xi-an

2013, 21(3): 179-183. doi: 10.11993/j.issn.1673-1948.2013.03.005

[Abstract](969) [PDF 312KB](585)

Abstract:
The Rayleigh distribution reverberation method based on the central-limit theorem cannot adapt to the high resolution active sonar system, while K-distribution model is more suitable for the statistical characters of the rever-beration in the condition of limited number of scatterers. Therefore, a new method is proposed in this paper to deduce the non-Rayleigh distribution reverberation by setting the random variables of K-distribution and simulating the reverbera-tion from matched filter. FIR filters are used to simulate multipath propagation, further to investigate the statistical characters of the reverberations of multipath propagation and direct wave. Simulation results indicate that the K-distribution based multipath propagation reverberation occupies obvious statistical characters of non-Rayleigh distri-bution in normalized reverberation intensity, probability of false alarm, and autocorrelation function.

Frequency Characteristics Analysis of Shallow Water Acoustic Channel for UUV Sonar

DENG Xin-wen, YE Hao-liang

2013, 21(3): 184-188. doi: 10.11993/j.issn.1673-1948.2013.03.006

[Abstract](1325) [PDF 332KB](554)

Abstract:
To improve the detection performance of underwater unmanned vehicle (UUV) sonar, the frequency charac-teristics of shallow water acoustic channel is analyzed. Shallow water acoustic channel is more complex than blue water acoustic channel. Due to multipath effect and reverberation, the propagation of acoustic wave is often deformed, result-ing in degradation in signal detection performance of sonar. The frequency characteristics of underwater acoustic chan-nel are analyzed with the data from tank experiment, lake and sea trials. Tank experiment shows the spread of signal frequency spectrum due to multipath effect. The data from lake and sea trials show that for the high-speed active sonar, the short-range reverberation is highly non-stationary, and the spread of point spectrum becomes more obvious. But the Doppler spread decreases with time. Therefore, the reverberation model algorithm based on stationarity assumption cannot be used to suppress the underwater vehicle sonar reverberation.

Analysis of Underwater Explosion Signals via Hilbert-Huang Transform

SUN Zhong-fu, SHENG Zhen-xin, LIU Rong-zhong, GUO Rui

2013, 21(3): 189-192. doi: 10.11993/j.issn.1673-1948.2013.03.007

[Abstract](957) [PDF 285KB](652)

Abstract:
A test was conducted to study the characteristics of underwater explosion acoustic signals. The test data are processed in this paper with the Hilbert-Huang transform(HHT) method to obtain the Hilbert spectrum. According to the Hilbert spectrum, the underwater explosion acoustic signals are analyzed, and the formation mechanism of local energy extreme point is discussed. The results indicate that the Hilbert spectrum can show the frequency distribution and the time-frequency characteristic of energy of the underwater explosion acoustic signals. Local energy extreme point is formed due to interaction of acoustic ray trajectories and sea bottom.

Attitude Measurement System with Low Power Consumption for Underwater Observation Platform

GUO Hu-sheng, YAN Bin, WU Zhi-dong

2013, 21(3): 193-196. doi: 10.11993/j.issn.1673-1948.2013.03.008

[Abstract](812) [PDF 221KB](669)

Abstract:
The work of the existing attitude measurement system of the underwater observation platform will be dis-turbed by the ocean wave. Aiming at this problem, a design scheme of micro-electro-mechanical system(MEMS) com-posed of a 3-axis micro acceleration sensor and a 3-axis magneto resistance sensor is given in detail. The system can get pitch, roll and azimuth angles of the underwater observation platform in real-time. Test data show that the system has the advantages of low power consumption, small size, low cost, and shock resistance, and it meets the precision requirement for attitude measurement of the underwater observation platform.

Sampling Correction of Steering Gear Control System for Autonomous Underwater Vehicle

WANG Qian, YAN Wei-sheng, FENG Kai

2013, 21(3): 197-201. doi: 10.11993/j.issn.1673-1948.2013.03.009

[Abstract](1323) [PDF 249KB](559)

Abstract:
The error correction for analog-to-digital(A/D) sampling by analog circuit processing is relatively mature. But it is relatively difficult to be implemented. And the digital correction has not been actually verified. In this paper, aiming at the sampling problem of steering gear control system for an autonomous underwater vehicle(AUV), the reason, proc-ess and result of generating sampling deviation are analyzed by considering the characteristics of the A/D sampling module on a TMS320F2812 chip, and the principles of sampling correction are described. Accordingly, graphic method and formula method are proposed for the error correction. In graphic method, the difference between duty cycle of actual pulse width modulation(PWM) and theoretical sampling value are compared for error correction through a graphical way. In formula method the theoretical formula is compared with actual output to get correction formula. Experimental results show that the steering gear control system achieves a good position tracking performance through internal digital cor-rection, and the control precision fully meets the design requirement of steady-state error.

Simulation on Torpedo Water Cooling Support System with a Spring Piston Damper

MA Wei-feng, PENG Bo, LEI Yun-long, WAN Rong-hua, LIANG Yue

2013, 21(3): 202-205. doi: 10.11993/j.issn.1673-1948.2013.03.010

[Abstract](944) [PDF 273KB](543)

Abstract:
To reduce the pressure oscillation of torpedo water cooling subsystem and avoid oscillation aggravation, a pressure oscillation model for torpedo water cooling support subsystem with a spring piston damper is established by using centralized parameter method. The frequency of the water cooling system with a spring piston damper is obtained by electro-hydraulic analogy. Experimental results verify that the spring piston damper can reduce pressure oscillation amplitude and change frequency of the water cooling system.

Thermal Dissipation Analysis of High-speed Turbine Impeller Based on Energy Method

GAO Xing, HUANG Ke, DUAN Hao

2013, 21(3): 206-212. doi: 10.11993/j.issn.1673-1948.2013.03.011

[Abstract](885) [PDF 1055KB](509)

Abstract:
Operation of high-speed turbine impeller dissipates energy. The variation of temperature is a key parameter for analyzing energy dissipation in its plastic deformation. This paper analyzes the relation between strain energy and heat dissipation of a high-speed turbine impeller on a vacuum test-bed via an established model by using analytical method, and obtains the effects of elastic strain energy and plastic strain energy on heat dissipation of the impeller. The temperature variation observed in experiment validates the computational result, which can provide theoretical reference to systemically analyze thermal dissipation in actual working conditions.

Modeling and Simulation of Underwater Shooting Forbidden Zone for Rocket Assisted Torpedo

LIN Zong-xiang, ZHOU Ming, SUN Yong-kan, GAO Dong-fei

2013, 21(3): 213-218. doi: 10.11993/j.issn.1673-1948.2013.03.012

[Abstract](834) [PDF 293KB](588)

Abstract:
The definition of rocket assisted torpedo (RAT) shooting forbidden zone and the division principle are given. Accordingly, the calculation models of shooting forbidden zones in initial searching phase, pursuing phase and re-searching phase of a rocket assisted torpedo are built by considering the characteristic of its underwater trajectory. The influences of some factors on the shooting forbidden zones are analyzed via simulation, and the result indicates that the torpedo homing distance and velocity, as well as the maximum velocity of target, are the key influencing factors. Further, the expression of RAT underwater shooting forbidden zone is simplified according to infaust instance.

A Revising Method of Leading Angle of Torpedo Trail

WU Zhi-dong, ZHU Wei-liang, YU De-xin

2013, 21(3): 219-223. doi: 10.11993/j.issn.1673-1948.2013.03.013

[Abstract](1266) [PDF 287KB](571)

Abstract:
Traditional method for estimating torpedo hit position by observation of torpedo trail brings big error. In this paper, the mathematical principle of the traditional method is analyzed, and mathematical models of turn angle shooting of a straight running torpedo are established through geometrical analysis. Moreover, the revising principle of the torpedo leading angle is explored by converting the encounter between torpedo and target into the encounter between torpedo fore-trail and target, and calculation models of the leading angle revision are constructed. In addition, the possible error in the revising course is analyzed. Simulation result verifies the feasibility and validity of the proposed method.

Discussion on the Problems in Torpedo Fuze-Warhead Matching

WANG Shu-shan, LU Xi, MA Feng, XU Yu-xin

2013, 21(3): 224-229. doi: 10.11993/j.issn.1673-1948.2013.03.014

[Abstract](1599) [PDF 207KB](773)

Abstract:
Torpedo fuze-warhead system is a subsystem of torpedo for terminal effects and task execution, and it directly re-lates to effectiveness of torpedo weapon system. In this paper, the fuze-warhead matching concept and its extension are out-lined, then the torpedo task in future naval warfare and the development of underwater heavily damaging torpedo warhead technology are addressed in order to clarify the importance of torpedo fuze-warhead matching. Furthermore, system frame-work of torpedo fuze-warhead matching is analyzed, and the main problems in research of torpedo fuze-warhead matching are discussed, such as typical target characteristics and vulnerability, power field structure of underwater explosion of warhead, analytical methods and means of fuze-warhead matching efficiency, and applications of virtual design and simulation tech-nologies.

Discussion on Naval Armament System Technology

PENG Ting-hua

2013, 21(3): 230-233. doi: 10.11993/j.issn.1673-1948.2013.03.015

[Abstract](807) [PDF 105KB](670)

Abstract:
Starting with the concept of naval armament system, the development process of the naval armament system technology is summarized, and the position and function of the naval armament system technology in naval armament development are analyzed. Further, the connotation of naval armament system technology, and the objects and contents in studying naval armament system technology are determined, thus a preliminary theoretical system is established. In addition, the development trend and features of naval armament system technology are described.

Review of Fusion Recognition Technology for Underwater Target

XIA Qing-sheng, LIU Yi-hai

2013, 21(3): 234-240. doi: 10.11993/j.issn.1673-1948.2013.03.016

[Abstract](1346) [PDF 329KB](611)

Abstract:
Information fusion techniques, which can help to effectively reduce or eliminate the measuring uncertainty of distributed sensors′ signal and fuse more comprehensive original vessel radiated signals, have been widely used in vari-ous military and civilian fields, and have attracted more concerns in the world. In this paper, the existing most accepted function models of the fusion systems are summarized, and a three-level (data-feature-decision) underwater automatic target recognition (ATR) system model is proposed. Subsequently, several commonly used fusion algorithms based on the probability theory, the data classification theory, and the artificial intelligence theory are presented, and their advan-tages, disadvantages and application constraints are analyzed. Moreover, the development trend of the underwater target fusion recognition system based on multi-sensor system, the existing problems, and the solutions to these problems are all discussed.

2013 Vol. 21, No. 3

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