6000m深海拖曳系统动力响应计算

本文数值计算了６０００ｍ深海单拖体和双拖体拖曳系统的动态响应，特别是研究了拖船的垂荡运动对拖体定高性的影响。对于双拖体系统，本文对第二拖体在水中的重量、联接两拖体的缆索长度及其在水中重量等因素对第二拖体定高性的影响进行了详细的计算、分析。计算表明，采用双拖体系统可大大提高系统的定高性。     

Study on the Configuration of Towed Flexible Cables

Based on the fundamental equation of flexible cable dynamics for a towed system, an easily solved mathematical model is set up in this paper by means of appropriate simplification. Several regular patterns of spatial motion of towed flexible cables in water are obtained through numerical simulation with the finite difference method, and then modification and verification by trial results at sea. A technical support is provided for the towing ship to maneuver properly when a flexible cable is towed. Furthermore, the relations between two towed flexible cables, which are towed simultaneously by a ship, are investigated. The results show that the ship towing two flexible cables is safe under the suggested arrangement of two winches for the towing system, and the coiling/uncoiling sequences of the cables as well as the suggested way of maneuvering.     

海洋测量水下拖曳设备的位置计算方法研究

针对海洋测量水下拖曳设备位置确定问题,综合考虑拖缆受力、海流影响以及水下拖体的运动性质,建立了水下拖曳设备的位置计算模型,并仿真计算分析了测量船在不同航行状态下拖曳设备位置确定的规律,探讨了不同海流效应对拖曳设备位置确定的影响。仿真计算结果表明,在海洋动态环境作用下,拖缆各方向的偏移明显呈曲线形状,非简单几何运算所确定。测船各方向的运动均可对水下拖体的位置在相应方向产生一定影响,而水下拖体位置的变化量小于测船拖点位置的变化量。海流对水下拖曳设备定位可造成数米的偏差,需进行相应改正。建议可考虑采取船载式ADCP实时测流辅助水下拖曳设备定位的工作模式。     

Ray Theory Application in Long Baseline System

The long baseline (LBL) system is widely used to locate and track autonomous underwater vehicles (AUV) through acoustic communication.Three important issues are presented here in LBL system application with AUV.Those issues which regard the normal acoustic communication between LBL system and AUV are the depth of towed array,the length of beacon cable,and the effective area of the AUV.The first issue is the key of the LBL system,which ensures the normal communication between towed array and beacons.The second issue which impacts the normal communication from the AUV to beacons in available range should be considered after the first one has been settled.Then the last issue determines the safe work area of the AUV.The ordinary differential equations (ODE) algorithm of ray is deduced from Snell′s law.The ODE algorithm is applied to obtain sound rays from sound source to receiver.These problems are solved by the judgment that whether rays pinging from a sound source arrives at a receiver.The sea trial shows that these methods have much validity and practicality.     

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.     

A constant tension winch: Design and test of a simple passive system

A constant tension winch controller has been designed to minimize peak tension loads encountered while towing heavy gear in rough sea conditions. The control unit consists of a pressure relief valve inserted in the hydraulic circuit of the winch. Operational tests with a towed plankton net system showed significant reduction in the cable tension peaks and marked improvement in the towed system behaviour.     

近海底高分辨率地震探测系统设计与实现

受大深度水体的影响,传统的海面拖曳式多道地震技术在进行深水地层探测时,目标地层深度处的菲涅耳半径非常大,水平分辨率低,难以满足海域天然气水合物高精度探测需求。针对海面拖曳式地震探测技术存在的上述问题,设计了一套可以在2000 m水深近海底作业的地震探测系统。应用耐压透声发射阵技术,克服了20 MPa外压环境和瞬时内压冲击对等离子体震源子波幅频特性的不利影响,研制的深拖等离子体震源的声源级达到214 dB,主频低于1000 Hz;水下控制中心采用集成SoC片上系统设计,可以对震源进行定距激发控制,进行近海底多道地震数据的连续采集。系统在2019年深海试验拖曳最大深度达2025 m,测试剖面数据显示最大地层穿透深度达380 m,纵向分辨率<2 m,横向分辨率<10 m,为深水海域沉积地层的深拖高分辨率地震探测提供了技术支撑。     

Parameters influence on maneuvered towed cable system dynamics

The dynamic response of a towed cable system to ship maneuver is parametrically simulated. Three dimensionless parameters influence on towed cable system maneuverability is investigated. They are ratio of total length to turning radius R/L, ratio of cable mass to vehicle mass σ, and ratio of mass unit length to hydrodynamic force w/r. An oscillatory motion of towed vehicle is found in simulation of spiral towed courses. Features of this oscillation in different spiral courses are compared. The sharp turns, gradual turns and their transient states of towed cable dynamics for different course directions are discussed extensively. According to the characters of transient states and horizontal trajectories evolution of maneuvered cable system, the dynamic behaviors can be divided into three situations in Fig. 8 turning maneuvers. The behavior of towed cable system during a zigzag turning course is simulated in the end. Two ingredients of heave motion are found during small ratio of turning radii to length in this course. The primary damp to initial turning becomes weak and the response to alternative turns plays a more and more important role. The damping properties of the transient behavior in different maneuvers show a periodical invariance to σ during some turning maneuvers.     

A motion-compensated launch/recovery crane

Oceanographic instrumentation towed from a surface platform is normally subjected to unwanted vertical motion imparted by the rolling, heaving, and pitching of the platform. This motion can cause severe shock-loading conditions in the tow cable and induces unplanned depth variations that reduce the instruments' resolution. This article discusses a unique motion-compensation system for use with towed instrumentation that eliminates shock loading and minimizes depth variation. The system is operational in sea states as high as 5 and effectively decouples 96% of the vessel's motion.     

埕岛油田海底管线拖管技术

介绍了埕岛油田海底管线的陆地发送技术,对拖管施工工艺进行了计算和受力分析,结合实际,采用多种拖管方法完善了适应滩海和极浅海海域海管铺设工艺。     

多参数拖曳荧光计系统现场实验研究

本文描述了多参数拖曳荧光计系统在船模水池和海上进行拖体水动力特性试验,得出：在１０ｋｎ以内的任意拖曳速度均能水平稳定拖曳,而纵倾角≤±２　的拖点位置;拖索张力Ｔ与拖体速度　之间的关系为Ｔ＝４７十３１．８　２．０８;拖曳速度为１０ｋｎ时,水动迫沉力约为９５０ｋｇｆ,升阻比约为２．４～２．５,满足了拖曳系统的迫沉要求。海上性能试验与应用实验表明：该拖曳系统的荧光传感器对水体、荧光示踪染料、悬浮颗粒物具有很高的分辨率;对罗丹明Ｂ水溶液的浓度检测范围为１×１０－７～１×１０－３ｍｇ／ｄｍ３;对悬浮物的浓度检测范围为２～２０００ｍｇ／ｄｍ３,使该系统广泛地用于海洋环境检测和评价工程任务中。     

水下拖曳升沉补偿系统水动力数学模型研究

建立变缆长的水下拖曳升沉补偿系统水动力学偏微分方程组和边界条件.拖缆动力学模型基于Ablow and Schechter模型,拖体采用水下运载体六自由度方程模拟,运用有限差分法离散偏微分方程组和牛顿迭代法计算变缆长情况下拖体深度与拖缆各点张力的动态取值.数值计算结果表明采用收放拖缆的升沉补偿方法能够有效削弱母船升沉运动对拖体深度和拖缆张力的影响.     

Dynamic modeling of cable towed body using nodal position finite element method

This paper analyses nonlinear dynamics of cable towed body system. The cable has been modeled and analyzed using a new nodal position finite element method, which calculates the position of the cable directly instead of the displacement by the existing finite element method. The newly derived nodal position finite element method eliminates the need of decoupling the rigid body motion from the total motion, where numerical errors arise in the existing nonlinear finite element method, and the limitation of small rotation in each time step in the existing nonlinear finite element method. The towed body is modeled as a rigid body with six degrees of freedom while the tow ship motion is treated as a moving boundary to the system. A special procedure has been developed to couple the cable element with the towed body. The current approach can be used as design tool for achieving improved directional stability, maneuverability, safety and control characteristics with the cable towed body. The analysis results show the elegance and robustness of the proposed approach by comparing with the sea trial data.     

An active source electromagnetic sounding system for marine use

Instrumentation has been developed for carrying out active source electromagnetic sounding experiments in the deep oceans. Experiments of this type are directly and uniquely sensitive to the presence of molten or partially molten material, to temperature structure and to the porosity of upper crustal rocks such as those that accommodate hydrothermal circulation systems. Electromagnetic sounding experiments therefore represent an extremely desirable addition to the existing range of geophysical techniques for studying geological processes in thermally, hydrothermally or magmatically active regions—for example, at oceanic spreading centres.The instruments can be operated in regions of rugged, unsedimented sea bottom terrain, and are designed for investigating the distribution of electrical conductivity within the oceanic crust and uppermost mantle. The instrumentation consists of a deep towed, horizontal electric dipole transmitter and a set of free-fall, sea bottom, horizontal electric field recording devices.The transmitter is a deep-towed instrument, which is provided with power from the towing ship through a conducting cable. The transmitter package is fitted with an integral echo sounder, which allows it to be towed safely a short distance above the seabed. Electromagnetic signals are transmitted from a neutrally-buoyant antenna array, which is streamed behind the deep tow.The sea bottom receiving instruments each consist of a recoverable package which contains the instrumentation and digital recording system, an acoustic release unit, four low-noise, porous electrodes arranged in two orthogonal, horizontal dipoles, and a disposable bottom weight.The instruments have been used at sea on three occasions. On their most recent use, active source signals were successfully recorded during an experiment to investigate crustal magmatism and hydrothermal circulation beneath the axis of the East Pacific Rise.     

Long-range sonar mapping of the continental shelf

Recent experiments in the shallow waters of the continental shelf off the west coast of Scotland have shown that it is possible to obtain geologically useful sonographs from a towed low-frequency side-scan sonar (GLORIA project) out to long ranges. Frequency-modulated pulses of 2-sec duration, centred at 6.4 kHz, with an acoustic power of 10 kW were transmitted, and the received energy was processed by a linear correlator. A maximum range of 13 km was achieved under both isothermal and stratified water conditions; however the most even irradiation of the sea floor was obtained when the water was isothermal, and under stratified conditions the maximum range could be reduced to 5 km or less if the sonar array was towed at a depth which lay within any strong temperature gradient in the water column.Examples of isometric records are shown, and it is suggested that mosaics could be built up from such records, obtained at a coverage of 170 km²/hour.     

Porosity determinations of sediments in Knight Inlet using a transient electromagnetic system

A newly developed towed transient electromagnetic (TEM) system is capable of measuring the electrical conductivity of the uppermost 5–10 m of sediments on the sea floor. The profiles of conductivity may be interpreted to give the porosity and likely texture of the bottom sediments. Recent tests of the system have demonstrated that data may be collected continuously in a surveying mode. Results from Knight Inlet, British Columbia, are in good agreement with sea floor samples from the area. Applications for the system include the rapid identification of sediment types for dredging operations, geotechnical surveys, or reconnaissance mapping of Quaternary geology.     

Combined Geoacoustic Inversion of Propagation and Reverberation Data

Sonar performance predictions in shallow water are strongly dependent on good knowledge of the geoacoustic and scattering properties of the seabed. One technique to extract information about the bottom is to use a towed source and a towed horizontal array. This towed system has been shown to be applicable for characterizing the bottom properties locally by inversion of the acoustic signals received directly on the towed array at short ranges. The same towed system has also been applied to extract bottom properties from long-range reverberation data providing effective bottom properties over a large area. However, independent geoacoustic inversion of the short-range propagation and long-range reverberation data can introduce low sensitivity and uncertainty in the extracted bottom properties. An attempt to resolve this low sensitivity and ambiguity is made by a simultaneous geoacoustic inversion of short-range propagation and long-range reverberation data with the intention of constraining the possible solutions of the bottom properties.      

Computer aided piloting of a deeply towed vehicle

An instrumented vehicle is towed at the end of a 5 km long cable, gathering data about the deep sea floor and near-bottom water column. Although bottom-moored acoustic transponders are used to determine the vehicle and ship positions precisely and in real time, predicting the ship manoeuvers required to bring the vehicle over an area of interest on the sea floor is far from trivial for the ship driver. Computer software has been developed which recommends courses for the ship to steer so that the vehicle will pass near a desired target. In trials at sea, the computer steered the vehicle 80, 40 and 85 m from pre-selected targets. Analysis of the causes of the misses suggests future developments which may reduce the miss distance, provide information on current structure of the water column, and reduce the level of skill and attention required of the vehicle pilot.     

深水声学拖曳系统

介绍了我国自主设计和研制的深水声学拖曳系统,它的最大工作水深4000m,安装有高分辨率测深侧扫声纳,可在近海底工作获得高分辨率的海底地形地貌和温盐深等数据.它的测深覆盖范围600m,侧扫覆盖范围800m,垂直航迹分辨率5cm,最小可检测高度10cm,测深分辨率高于目前的多波束测深系统.该系统已进行了湖试和海上锚泊试验.该系统的研制成功将对开展大陆架勘查,探测和开发国际海底资源发挥重要作用,拖曳系统中高分辨率测深侧扫声纳还可装船安装,在大陆架水域进行高分辨率海底地形地貌测绘.