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1.
P.J. Wingham 《Ocean Engineering》1983,10(1):1-32
The measured drag characteristics of a variety of cable fairings are reviewed and compared with those of bare cables. The effect of cable inclination angle has been studied and an empirical rule developed for dealing with faired cables, the hydrodynamic properties of which are shown to depend significantly on the section shape of the fairing.Non-dimensional cable functions are tabulated for both bare and faired cable profiles and applied to show how the addition of fairings can improve the towing performance of a given system.Simple formulae are developed for calculating faired cable system properties and for assessing the effect of fish drag on the depression angle. 相似文献
2.
P.J. Wingham 《Ocean Engineering》1984,11(3):281-313
The phenomenon of tow-off, or kiting, associated with faired cable systems has been studied in order to identify probable causes and demonstrate their effects. Three-dimensional cable profiles have been computed embodying experimentally determined values of all hydrodynamic quantities. The work encompasses fish induced and fairing induced tow-off, with light and heavy fairings, and provides generalised data for estimation purposes plus examples of the variation with towing speed and scope of the tow-off angles and fish displacements to be expected of a typical towed system. 相似文献
3.
海洋监测拖曳系统中拖缆导流套设计 总被引：2，自引：0，他引：2
拖缆导流套是提高海洋监测拖曳系统效能的有效手段之一.阐述了导流套的功能,分析了导流套的受力,以及拖缆导流套设计中要考虑的若干问题,并介绍了自行设计的导流套性能. 相似文献
4.
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. 相似文献
5.
D.A. Chapman 《Ocean Engineering》1984,11(1):23-64
The hydrodynamic forces and moments that act on a towed fish are described and related to fundamental static and dynamic towing characteristics. It is shown that, when the fin height is reduced almost to the point giving neutral stability in pitch, the fish maintains almost constant pitch attitude while it is forced to heave or surge by ship motion transmitted down the cable.Wind tunnel tests provide the necessary hydrodynamic data for a computer simulation in two dimensions of the Bath Mk 3 sonar fish towed on faired cable. The results show that the magnitude of the pitch attitude variations of the fish can be greatly reduced by decreasing the fin size, with further reduction being possible by correctly locating the pointwhere the cable is attached to the fish. It is also shown that decreasing the fin size reduces the magnitude of the tension variations in the cable, thereby lowering the probability that the cable will go slack.These results generalise to a large class of towed systems using either or bare cable, and a formula is included by which the magnitude of the ship-inducing pitching motion of a fish can be estimated, given the necessary hydrodynamic data.Possible difficulties associated with towing a low stability fish are considered and a method is included for assessing the minimum stability likely to be necessary to achieved satisfactory towing behaviour. 相似文献
6.
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. 相似文献
7.
Measurements of towed body motion in a laboratory towing tank have validated the mathematical model used as a basis for predicting body and cable dynamic behaviour under seagoing conditions. 相似文献
8.
Comprehensive wind tunnel measurements have been made of the drag coefficients of both the body and the faired cable of a towed system. The drag data has been embodied in theoretical calculations of the depth attained in tow, at speed up to 3 m s−1 (6 knots) with scopes up to 135 m (440 ft). The agreement with sea trial observations is excellent.The work has highlighted the importance of accounting for the variation of faired cable drag with cable angle and has shown that the drag increments due to gaps and misalignments between individual fairing elements cannot be ignored.Methods are derived for estimating these effects for application to other faired cable towed systems. 相似文献
9.
In this paper,the dynamic response of undersea -+towed systems is numerically simulated.Atwo body towed system is especially considered in detail.The factors influencing the heave oftowed-bodies,such as the weight of the towed-body(in sea water),the length and the weight(in sea water)per unit length of the cable between towed-bodies and towing ship,are investigated in detail.Calculationsshow that the two-body towed system can greatly increases the stability of the towed system. 相似文献
10.
波浪作用下缆船拖带系统非线性运动数值模拟 总被引：1，自引：0，他引：1
基于船舶操纵性运动方程和拖缆的三维动力学运动方程,提出了被拖点位置匹配的方法,建立了拖船—拖缆—被拖船系统整体非线性拖带动力学模型。为了考察被拖船航向稳定性与横向稳性的关系以及波浪载荷作用的影响,被拖船采用水平面四自由度运动方程,并引入了波浪的作用力和力矩。拖船采用PD控制方法较真实地模拟了拖船航向改变的运动过程。对一个拖船—拖缆—被拖船系统(5 000 t的拖船和3 000 t的被拖船)在时域内进行了规则波浪作用下拖带运动的模拟,计算结果表明被拖带船舶在波浪中运动呈现运动稳定、不稳定和临界状态3种可能的特性。根据模拟计算结果,认为波浪中拖带航向稳定是被拖带船舶保持稳性的必要条件。 相似文献
11.
Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）. 相似文献
12.
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。 相似文献
13.
The behavior of a long cable towed at slow speeds through the ocean depends in a complex fashion on the path followed by the towing ship relative to the water. A cable simulation program was used to characterize the response of the cable by using idealized towing ship maneuvers as input to the program. The response of the cable was noted and it was found that the behavior of the cable was strongly dependent on the fundamental period of the towing vessel maneuvers. Sinusoidal deviations of the towing ship from a straight towing track resulted in delayed and reduced excursions of the towed vehicle from the tract; the estimated response ratio varied from 0·002 to 0·800, depending both on the period of the deviations (periods ranged from 5·5 to 4·0 hr) and on the towing depth (2 or 6 km). The ship's speed was 3 km/hr. The time lag between ship motion and vehicle response was approximately 0·5 hr for the shallow case and 1·3 hr for the deep case. Simulations runs of a low dragk (faired) cable showed that the behavior of the vehicle when towed at a depth of 6 km was similar to that obtained with a conventional cable at 2 km depth. The response of the towed vehicle to a right-angle turn of the towing ship was investigated and a generalized model of the response developed. The effects of a controllable side force on the towed vehicle were also simulated and it was noted that a deviation (2-hr period) of the towed vehicle from a straight-line track could be reduced from 40 to 2 m by impressing a side force on the vehicle with an average magnitude of 150 newtons (30 lb). 相似文献
14.
Hae-Hoon Park 《Ocean Engineering》1993,20(2)
An indirect tension measurement method of a towing cable in midwater or a buoy cable is proposed using underwater acoustic positioning systems, etc., to give the in-water cable tension. The most simple and traditional cable tension measurement method is to apply a mechanical tension meter at the one end of the cable, but the method has limits in the aspects of continuous monitoring and manual operation. However, the technique in this study is to apply the Pode's analysis of the equilibrium configuration and tension of a flexible twine, in which the cable tension is given as a function of the geometric positions of both ends of the cable. A set of nonlinear integral equations is formulated and solved numerically by the Newton-Raphson method. Then the inclination angles and the tensions at the lower and the upper ends of the cable could be obtained. The derived method enables us to track a towed object, to measure the tension of a towing cable or a buoy cable and is also applicable to the remotely operated vehicle (ROV) tethered to a mother ship. 相似文献
15.
针对已建成科考船加装中水多波束的实际技术需求,结合中水多波束加装科考船的船舶线型及其系统安装要求,通过设计两种不同类型的导流罩线型,并与船体线型一体化进行计算流体动力学(Computational Fluid Dynamics,以下简称CFD)仿真分析,了解实船舶航行过程中船体型线和导流罩型线之间的相互影响,分别对圆弧型导流罩和折角型导流罩的防气泡性能和阻力性能进行了CFD预报和分析。最后经海试验证折角型导流罩能够完全满足中水多波束的安装线型流线及湍流动能的性能指标,为科考船多波束导流罩的设计安装或加装提供一定的借鉴和参考作用。 相似文献
16.
In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the platform wrapped with fairing structure and separated from the retrieval unit is described. The suppression effect evaluation based on the correlation theory of sound pressure and particle velocity for spherical wave in infinite homogeneous medium is proposed and the difference value between them is used to evaluate the hydrodynamic restraining performance of the bottom-mounted platform under far field condition. Through the sea test, it is indicated that the platform with sparse layers fairing structure (there are two layers for the fairing, in which the inside layer is 6-layers sparse metal net, and the outside layer is 1-layer polyester cloth, and then it takes sparse layers for short) has no attenuation in the sound pressure response to the sound source signal, but obvious suppression in the velocity response to the hydrodynamic noise. The effective frequency of the fairing structure is decreased below 10 Hz, and the noise magnitude is reduced by 10 dB. With the comparison of different fairing structures, it is concluded that the tighter fairing structure can enhance the performance of sound transmission and flow restraining. 相似文献
17.
水下拖缆物理参数不均匀会影响拖缆的动力特性,研究非均匀拖缆的参数变化对拖缆动力特性的影响有一定的工程实际意义。建立了拖曳系统运动的三维数学模型,推导出了水下非均匀拖缆的稳态运动控制方程,在首尾两端加上相应的定解条件,直接求得或使用嵌套二分法求得非均匀拖缆在端点的初始值,进而求解稳态动力学方程。借助文献中的拖缆—海底拖车系统算例,通过计算结果的对比,验证了数学模型及计算方法的正确性。通过四阶龙格库塔法进行数值仿真计算,得到了稳态解,分析了非均匀拖缆自身物理参数变化对缆绳系统稳态运动的影响。结果表明,非均匀拖缆的切向阻力系数、法向阻力系数、直径和密度变化会影响稳态缆形和张力分布,影响的程度各不相同。最后给出了两个尾拖船系统非均匀拖缆的稳态运动算例。 相似文献
18.
Time-domain numerical simulation of ocean cable structures 总被引：2，自引：0，他引：2
This paper describes the numerical features of WHOI Cable, a computer program for analyzing the statics and dynamics of oceanographic cable structures. The governing equations include the effects of geometric and material nonlinearities, bending stiffness for seamless modeling of slack cables, and a model for the interaction of cable segments with the sea floor. The program uses the generalized-α time integration algorithm, adaptive time stepping, and adaptive spatial gridding to produce accurate, stable solutions for dynamic problems. The nonlinear solver uses adaptive relaxation to improve robustness for both static and dynamic problems. The program solves surface and subsurface single-point mooring problems, multi-leg and branched array systems, and towing and drifting problems. User specified forcing can include waves, currents, wind, and ship speed. 相似文献
19.
20.
深海观测系统脐带缆形态分析及计算 总被引：3，自引：0，他引：3
通过对水下拖曳系统脐带缆索的受力情况、形态进行分析，建立了三维空间缆索的物理模型和数学模型，并在此基础上编制了计算程序，对6000m深海观测系统脐带缆的性状进行了模拟计算，其结果为深拖系统最佳缆长的确定提供了理论依据。 相似文献