共查询到20条相似文献，搜索用时 31 毫秒
1.
The dynamic behavior of a towed cable system that results from the tow ship changing course from a straight-tow trajectory to one involving steady circular turning at a constant radius is examined. For large-radius ship turns, the vehicle trajectory and vehicle depth assumed, monotonically and exponentially, the large-radius steady-state turning solution of Chapman [Chapman, D.A., 1984. The towed cable behavior during ship turning manoeuvers. Ocean Engineering 11, 327–361]. For small-radius ship turns, the vehicle trajectory initially followed a corkscrew pattern with the vehicle depth oscillating about and eventually decaying to the steady-state turning solution of Chapman (1984). The change between monotonic and oscillatory behavior in the time history of the vehicle depth was well defined and offered an alternate measure to Chapman's (1984) critical radius for the transition point between large-radius and small-radius behavior. For steady circular turning in the presence of current, there was no longer a steady-state turning solution. Instead, the vehicle depth oscillated with amplitude that was a function of the ship-turning radius and the ship speed. The dynamics of a single 360° turn and a 180° U-turn are discussed in terms of the transients of the steady turning maneuver. For a single 360° large-radius ship turn, the behavior was marked by the vehicle dropping to the steady-state turning depth predicted by Chapman (1984) and then rising back to the initial, straight-tow equilibrium depth once the turn was completed. For small ship-turning radius, the vehicle dropped to a depth corresponding to the first trough of the oscillatory time series of the steady turning maneuver before returning to the straight-tow equilibrium depth once the turn was completed. For some ship-turning radii, this resulted in a maximum vehicle depth that was greater than the steady-state turning depth. For a 180° turn and ship-turning radius less than the length of the tow cable, the vehicle never reached the steady-state turning depth. 相似文献
2.
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. 相似文献
3.
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
4.
J.-G. Dessureault 《Ocean Engineering》1976,3(2):99-111
“Batfish” is a streamlined vehicle developed to house fast-responding oceanographic sensors. It is towed behind a ship or small vessel and its depth is controlled from the vessel by a manually or automatically produced command signal. Variable-angle wings permit the vehicle to be lowered and a novel control surface, which eliminates the need for heavy ballast, assures lateral stability. There are two models: the standard and the wide-wing Batfish. The standard Batfish has collected temperature and conductivity data at depths of up to 200 m when towed at 10–25 km/hr, and the wide-wing Batfish at depths to 400 m when towed at 10–16km/hr. 相似文献
5.
V. A. Blinkov 《Physical Oceanography》1999,10(2):183-192
We describe the characteristics of a towed complex used for measurements in the upper layer of the ocean under the conditions
of periodic deepening and lifting (scanning) of a carrier with sensors connected with the ship by a weight-carrying cable
of constant lengt. For a maximum scanning range of 0–200 m and a towing speed of up to 12 knots, the measurements were performed
every 1.5–2.0 km. The minimum vertical scale of recorded temperature and conductivity inhomogeneities is 0.05–0.08 m. We present
the results of measurements carried out by the towed complex in a section of the frontal zone in the north-east part of the
Tropical Atlantic.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 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.
An experimental set-up is developed and proved to be effective for laboratory study of an underwater towed system. The experimental technique gives a practical method for monitoring the kinematic and dynamic performance of an underwater towed system in a ship towing tank. Both the theoretical and experimental results in the investigation indicate that the hydrodynamic response of a towed vehicle to the wave induced motion of a towing ship can be significantly reduced by applying a two-part tow method. A comparison of the numerical and experimental results in the investigation demonstrates that the numerical simulation results are close to the experimental data, overall agreement between experimental and theoretical results is satisfactory. The results qualitatively verify the mathematical model of a two-part underwater towed system proposed by Wu and Chwang [Wu, J., Chwang, A.T., 2000. A hydrodynamic model of a two-part underwater towed system. Ocean Engineering 27 (5), 455–472]. 相似文献
8.
9.
A three-dimensional model of a two-part underwater towed system is studied. In the model, the governing equations of cables are established based on the Ablow and Schechter method. The boundary conditions for the two-part underwater towed system are derived. The six-degrees-of-freedom equations of motion for submarine simulations are adopted to predict the hydrodynamic performance of a towed vehicle. The established governing equations for the system are then solved using a central finite difference method. In this paper several algorithms are used to solve this special form of finite difference equations. The results in this paper indicate that the two-part underwater towed system improves the dynamic behavior of the towed vehicle and is an easy way to decouple the towing ship motion from the towed vehicle. Because the model uses an implicit time integration, it is stable for large time steps and is an effective algorithm for simulation of a large-scale underwater towed system. 相似文献
10.
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
11.
基于模糊神经网络理论对水下拖曳体进行深度轨迹控制 总被引：2，自引：0，他引：2
以华南理工大学开发的自主稳定可控制水下拖曳体为研究对象,首先通过水下拖曳体在拖曳水池样机中的试验取得试验数据后作为训练样本,采用LM BP算法,建立基于神经网络理论构建的可控制水下拖曳体轨迹与姿态水动力的数值模型。在此基础上设计了一个控制系统,它主要由两部分组成:基于遗传算法的神经网络辨识器和基于模拟退火改进的遗传算法的模糊神经网络控制器。以满足预先设定的拖曳体水下监测轨迹要求为控制依据,由控制系统确定为达到所要求的运动轨迹而应采用的迫沉水翼转角,以此作为输入参数,通过LM BP神经网络模型的模拟计算预报在这一操纵动作控制下的拖曳体所表现的轨迹与姿态特征。数值模拟计算结果表明:该系统的设计达到了所要求的目的;借助这一系统,可以有效地实现对拖曳体的深度轨迹控制。 相似文献
12.
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
13.
14.
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. 相似文献
15.
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
16.
17.
Dynamic Analysis of Towed and Variable Length Cable Systems 总被引：2，自引：3，他引：2
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. 相似文献
18.
D. E. Calkins 《Ocean Engineering》1999,26(11):1193
The objective of this exercise was the development of a computer simulation of a US Navy towed system (towed body and line array) capable of near real-time predictive capabilities. The purpose of the computer simulation was to be able to determine the lateral motion of the towed body in response to ship maneuvers. The theoretical approach was to develop a spatial-domain computer simulation of each of the towed system components treated as a system, and then develop a “metamodel” of the response by using simple algebraic expressions. At-sea trials were conducted aboard US Navy vessels to verify the simulation and fine-tune its performance. 相似文献
19.
A three-dimensional dynamic analysis of a towed system 总被引：1，自引：0，他引：1
Joël V. Sanders 《Ocean Engineering》1982,9(5):483-499
The three-dimensional configuration of a towed cable-body system during prescribed towship maneuvers is determined. Bending resistance and inertia terms are not retained in the towing model; methods are described for ascertaining when these effects are negligible. A physical finite difference formulation is employed to develop the discretized equations of motion, and the system configuration is advanced in time using a Runge-Kutta recurrence algorithm. The response of a reference towed system to a typical maneuver is presented graphically. 相似文献
20.
Numerical simulation of undersea cable dynamics 总被引：7，自引：0，他引：7
A fully three-dimensional code has been written to compute the motion of a towed cable. The code is based on a robust and stable finite difference approximation to the differential equations derived from basic dynamics. A 3500-ft (1.07 km) cable pulled at 18.5 knots (34.3 km hr−1) through a circular turn of 700 yd (0.64 km) radius has been computed in about half of the real time of the maneuver. The computed displacements are close to the measured ones; the changes in depth are within 2%. 相似文献