水下无人系统学报

Numerical Simulation of Ventilation Law for Supercavitating Vehicle

SUN Shi-ming, YAN Kai, CHEN Wei-zheng

2014, 22(2): 081-86. doi: 10.11993/j.issn.1673-1948.2014.02.001

[Abstract](1342) [PDF 1931KB](509)

Abstract:
To understand the ventilation law of a supercavitating vehicle in high Froude number flows, RANS equations and the volume of fluid (VOF) multiphase flow model are employed to simulate the ventilation law of a supercavitating vehicle in the case of small cavitation number. The distributions of velocity and pressure in ventilated supercavitation flow are described. The cavity shapes and the pressure along the cavity wall with different ventilation rates are compared, respectively. The ventilation laws at different natural cavitation number and Reynolds number are obtained, and simula-tion results agree well with experimental phenomena. Based on the calculation results and the dimension analysis, a new formula considering the influence of natural cavitation number is proposed to calculate the ventilation coefficient at high Froude number.

Modeling and Simulation of Inflation Process for Torpedo Inflatable Collar

CHENG Wen-xin, CAI Wei-jun, YANG Chun-wu, SUN Yuan

2014, 22(2): 087-90. doi: 10.11993/j.issn.1673-1948.2014.02.002

[Abstract](1086) [PDF 1092KB](585)

Abstract:
Reliability of inflation process of a torpedo inflatable collar directly influences the safe recovery of the tor-pedo. In order to understand the inflation mechanism of a torpedo inflatable collar, a theoretical model of inflation process of a torpedo inflatable collar is built to simulate the tank exhausting and torpedo inflatable collar inflation proc-esses based on the thermodynamic law. The variation rules of the parameters, such as the volume of inflatable collar, the inflation velocity, the tank pressure and the force on inflatable collar during inflation process, are obtained. The detail processes of torpedo speed changing and inflatable collar filling under critical depth is gotten by simulation of torpedo inflation process in the case of torpedo stop with speed. Simulation results illustrate that the parameters such as inflat-able collar inflation and residual gas pressure, as well as the variation rules of torpedo speed and depth, show good agreement with the experimental data. The proposed model may provide a theoretical tool for design of torpedo buoy-ancy equipment.

Real-time Estimation Method of Normalized Parameter for PGC Demodulation of Optical Fiber Hydrophone

ZHOU Shao-ling, YUN Xiao-hui

2014, 22(2): 091-95. doi: 10.11993/j.issn.1673-1948.2014.02.003

[Abstract](861) [PDF 1267KB](1224)

Abstract:
A real-time estimation method of normalized parameter is proposed to reduce the significant distortion in phase generated carrier(PGC) demodulation of optical fiber hydrophone due to offline estimation of normalized pa-rameter. The square differences of the amplitudes of two orthogonal signals at both current time point and previous time point are calculated, then the normalized parameter is obtained by calculating the ratio of two square differences. Simu-lations and experiments show that a correct normalized parameter can be achieved with the proposed method if signal amplitude is small. Experimental results indicate that when a small signal with peak amplitude of 0.3 radian is imposed to the hydrophone, the estimation error of normalized parameter gets less than 3%. Using the achieved normalized pa-rameter to demodulate the signal of the optical fiber hydrophone, signal to total harmonic distortion ratio is less than 48 dB, which meets the requirement for engineering application.

A Realization Method for Ambiguity Function of Wideband Pulse Train Signal

YUE Lei, LIANG Hong, YANG Chang-sheng

2014, 22(2): 096-99. doi: 10.11993/j.issn.1673-1948.2014.02.004

[Abstract](1080) [PDF 1089KB](706)

Abstract:
The ambiguity function of wideband pulse train signal is a powerful tool for signal analyzing and waveform designing, and a common method in detection and estimation. Realization of the ambiguity function firstly needs syn-thesizing replicas. However, directly copying scale extension of the sub pulse and multiplying different weights to syn-thesize replicas may cause most replicas vectors losing and information missing. In order to solve this problem, this paper adopts a new method for synthesizing replica signal, in which the entire pulse train is firstly compressed and then resampled. Simulation on the pulse train of linear frequency-modulated waveforms′ ambiguity function shows that the method is feasible and applicable to achieve ambiguity function of wideband pulse train signal.

Influencing Factors of Pulse Baseline Positioning Performance in Near Field

DONG Li-ying, CHEN Zhi-fei

2014, 22(2): 100-104. doi: 10.11993/j.issn.1673-1948.2014.02.005

[Abstract](954) [PDF 1646KB](732)

Abstract:
The equations of ranging and direction finding at the arrival time of leading pulse are deduced for pulse base-line positioning. The influences of the parameters of CW pulse, array, and sound source incident position on the per-formance of pulse baseline positioning are discussed. Simulation results show that the pulse baseline positioning can achieve better performance in the case of lower radiation frequency, larger array aperture, and the very source inci-dence against the array direction. Array number has little influence on the positioning performance, and with an increase in the range between sound source and array, the directional performance keeps stable, but the ranging performance decreases continuously.

An Equalization Algorithm for Underwater Acoustic OFDM Communication System Based on Fractional Fourier Transform

XU Wei, HU You-feng, WANG Xiao-zhou

2014, 22(2): 105-109. doi: 10.11993/j.issn.1673-1948.2014.02.006

[Abstract](1358) [PDF 1115KB](722)

Abstract:
The performance of traditional orthogonal frequency division multiplexing(OFDM) system will be greatly degraded if the orthogonality between sub-carriers is destroyed by the Doppler effect. To solve the problem, we present a new twice transform method for channel estimation and equalization based on the fractional Fourier transform(FRFT), discuss the principle and implementation process of the proposed method. In this method, the received data in frequency domain are equalized and then the equalized data are transformed into corresponding fractional Fourier domain to pro-vide a basis for engineering application of FRFT-OFDM system. Simulation results show that the performance of OFDM system based on the FRFT is improved efficiently, which compared with traditional OFDM system.

A Three-Channel Accurate Control Algorithm Based on Vector Principle

HAO Zhe, ZHANG Qin-nan, WANG Li-wen, WANG Zhong

2014, 22(2): 110-115. doi: 10.11993/j.issn.1673-1948.2014.02.007

[Abstract](922) [PDF 1545KB](752)

Abstract:
To launch a lightweight torpedo safely on different platform in shallow water, it is necessary to reduce the bag depth of a torpedo water-entry and prevent its “free running”. We deduce a three-channel accurate control algorithm based on vectorprinciple via vectorization of the error Euler angle. This accurate control algorithm can help to achieve the best decoupling of the torpedo kinematics, obtain stable control of a torpedo with large attitude water-entry, hence to reduce the bag depth and accurately control the torpedo course. Simulation indicates that the proposed algorithm is ap-plicable to launching lightweight torpedo on multi-platform in shallow water.

Analysis of Alignment Accuracy for Single-Axis Rotation Ring Laser Gyroscope SINS

LIU Yong-hong, LIU Ming-yong, XIE Bo

2014, 22(2): 116-120. doi: 10.11993/j.issn.1673-1948.2014.02.008

[Abstract](1226) [PDF 1224KB](673)

Abstract:
An alignment scheme for single-axis rotation ring laser gyroscope(RLG) strapdown inertial navigation system (SINS)is designed, and the error parameters of the inertial device affecting the alignment accuracy are analyzed. The ali- gnment scheme is validated by simulation, and the different errors of inertial devices corresponding to the alignment ac- curacy are compared. Simulation result indicates that the scale factor asymmetry error and the scale factor error of the vertical axis gyro exert significant effects on the alignment accuracy of course angle. This study may offer a reference for design of single-axis rotation RLG SINS.

Analysis on Properties of Molybdenum Alloy for Pneumatic Valve with Improvement Approaches

BAO Hai-ge, TONG Fa-song, WANG Tian-xiao

2014, 22(2): 121-125. doi: 10.11993/j.issn.1673-1948.2014.02.009

[Abstract](825) [PDF 2380KB](478)

Abstract:
Aiming at the crack problem in domestic pneumatic valves, both domestic and foreign molybdenum alloy pneumatic valves are compared in terms of chemical analysis, microstructure, and stretching performance. The compo-nents, metallurgies and plastic forming technologies of the molybdenum alloy in China and abroad are analyzed, and some improvement approaches are offered, such as adopting electron beam purification melting method after vacuum melting, and taking extrusive breakdown and multiple forging processes, which can meet the requirement of engineering test. These improvement approaches can improve the properties of molybdenum alloy for pneumatic valve.

Numerical Simulation of Hydrodynamics for Integrated Motor Propeller

ZHAO Fang-ze

2014, 22(2): 126-130. doi: 10.11993/j.issn.1673-1948.2014.02.010

[Abstract](1211) [PDF 2657KB](690)

Abstract:
Physical models of an integrated motor propeller and mathematical models of flow field are established, and the boundary conditions are determined to optimize the design of the integrated motor propeller. The software FLUENT is adopted to numerically simulate the inside flow fields. Thus, the distributions of pressure and velocity on the blade surfaces of rotor and stator are obtained, and the relationship among the propulsive thrust and efficiency of the integrated motor propeller and the running speed of a vehicle is gained under different conditions. As a result, the performance of the integrated motor propeller can be estimated on the basis of the simulation results.

Discussion on Torpedo Operation Test Scheme in Design Acceptance Phase

ZHANG Yuan-biao, WANG Hao, LI Chun-feng, YAN Rui-bing

2014, 22(2): 131-135. doi: 10.11993/j.issn.1673-1948.2014.02.011

[Abstract](1001) [PDF 1849KB](737)

Abstract:
Through increasing test items and enhancing assessment degree in design acceptance phase of a torpedo, we discuss the scheme of torpedo operation test in design acceptance phase with regard to the life profiles events in techni-cal position, such as storage, maintenance, preparing, transportation and attack check test under countermeasure condi-tion on the sea, and design a preliminary scheme of torpedo operation test with corresponding evaluation criterions of real shoot check test result for a torpedo. This study may facilitate torpedo operation test and evaluation in torpedo range.

An Evaluation Method of Sea States Adaptability for Airborne Torpedo

MA Hao-wen, HAN Zhao

2014, 22(2): 136-139. doi: 10.11993/j.issn.1673-1948.2014.02.012

[Abstract](1392) [PDF 1289KB](807)

Abstract:
Sea states adaptability under boundary condition is an important item in the test of underwater weapon. However, the sea states adaptability test of an airborne torpedo is difficult because of the restriction of some factors. In order to assess the sea states adaptability, the influencing factors of the sea states on operation process of an airborne torpedo are analyzed, such as the parachute-opening strength, water entry impact, and marine environment interference, and an evaluation method of sea states adaptability test for an airborne torpedo is hence presented. The availability of the present method is verified by test.

Grey Cluster Judgment Method for Comprehensive Performance Evaluation of Torpedo in Sea Trial

LI Fu-xiao, TIAN Zheng, ZHAO Wei, YANG Li-juan, YU Wei, LI Jie

2014, 22(2): 140-144. doi: 10.11993/j.issn.1673-1948.2014.02.013

[Abstract](1088) [PDF 1119KB](608)

Abstract:
The features of the evaluation indexes for a torpedo in sea trial are analyzed, and an evaluation indexes sys-tem of comprehensive performance for a single torpedo in sea trial is built. The analytic hierarchy process (AHP) is adopted to calculate the weights on the evaluation indexes. A new method for evaluating torpedo′s comprehensive per-formance in sea trial is presented based on the grey cluster theory. Simulation results show that the proposed method can not only evaluate comprehensive performance of a single torpedo, but also give comprehensive performance sequence of several torpedoes with same type, which may provide a reference for torpedo acceptance.

An Assessment Method for Operational Reliability in Sea Trial Based on Multi-stage Experimental Data

LIAO Fu-kui, ZHOU Chun-ming, ZHAO Min

2014, 22(2): 145-149. doi: 10.11993/j.issn.1673-1948.2014.02.014

[Abstract](959) [PDF 1090KB](542)

Abstract:
For solving the problem that the sea trial data cannot be used in operational reliability assessment due to the change of product technical condition in different stages, an assessment method for operational reliability in sea trial based on multi-stage sea trial data is presented by using the reliability stage growth model with ordered constraint bi-nomial distribution and the Bayesian statistics. Application results show that this assessment method can improve the utilization of the data from sea trial, and assess the operational reliability objectively and economically in sea trial.

Development of Torpedo Defence Systems of Foreign Surface Ships

XIAO Chang-mei, LI Heng, PENG Pei

2014, 22(2): 150-156. doi: 10.11993/j.issn.1673-1948.2014.02.015

[Abstract](1341) [PDF 2085KB](1848)

Abstract:
The characteristics of modern torpedoes are summarized. The development status of the surface ship’s torpedo defense systems in some western countries is discussed, the characteristics of the torpedo defense systems are analyzed, and their development trends are forecasted. It is suggested that the new concept defense weapons, such as anti-torpedo torpedo and supercavitating projectile, be taken as development direction of torpedo defense system of surface ship in future.

Review of Foreign Shipborne Assisted Torpedoes

LIANG Liang, JIA Yue, REN Lei

2014, 22(2): 157-160. doi: 10.11993/j.issn.1673-1948.2014.02.016

[Abstract](1023) [PDF 1221KB](859)

Abstract:
We briefly introduce the development of foreign shipborne assisted torpedoes and representative weapons, generalize the characteristics and basic operational processes of the ballistic and cruise assisted torpedoes, and compare their advantages and disadvantages. Furthermore, we analyze and forecast the development trend of the assisted torpe-does in terms of flight speed, attack distance, launch technology, instruction correction technology, and multiplatform collaboration against submarine.

2014 Vol. 22, No. 2

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