共查询到20条相似文献，搜索用时 22 毫秒
1.
Running attitudes of semi-displacement vessels are significantly changed at high speed and thus have an effect on resistance performance and stability of the vessel. There have been many theoretical approaches about the prediction of running attitudes of high-speed vessels in calm water. Most of them proposed theoretical formulations for the prismatic hard-chine planing hull. In this paper, running attitudes of a semi-displacement round bilge vessel are theoretically predicted and verified by high-speed model tests. Previous calculation methods for hard-chine planing vessels are extended to be applied to semi-displacement round bilge vessels. Force and moment components acting on the vessel are estimated in the present iteration program. Hydrodynamic forces are calculated by ‘added mass planing theory’, and near-transom correction function is modified to be suitable to a semi-displacement vessel. Next, ‘plate pressure distribution method’ is proposed as a new hydrodynamic force calculation method. Theoretical pressure model of the 2-dimensional flat plate is distributed on the instantaneous waterplane corresponding to the attitude of the vessel, and hydrodynamic force and moment are estimated by integration of those pressures. Calculations by two methods show good agreements with experimental results. 相似文献
2.
A numerical simulation algorithm based on the finite volume discretisation is presented for analyzing ship motions. The algorithm employs a fractional step method to deal with the coupling between the pressure and velocity fields. The free surface capturing is fulfilled by using a volume of fluid method in which the interface between the liquid (water) and gas (air) phases are computed by solving a scalar transport equation for the volume fraction of the liquid phase. The computed velocity field is employed to evaluate the acting forces and moments on the vessel. Using the strategy of boundary-fitted body-attached mesh and calculating all six degrees-of-freedom of motion in each time step, time history of ship motions including displacements, velocities and accelerations are evaluated.To verify the proposed algorithm, a series of verification tests are conducted. First, a two-dimensional asymmetrical wedge slamming is simulated as a simple type of a common case for high-speed vessels. Then, the steady-state forward motion of a high-speed planing catamaran is investigated. Results of both test cases show good agreement with experimental data. It is concluded that the proposed algorithm can be a promising strategy for both performance prediction and design of high-speed vessels. 相似文献
3.
Mohammad Saeed SEIF Ebrahim JAHANBAKHSH Roozbeh PANAHI Mohammad Hossein KARIMI 《海洋工程》2009,(3):517-528
High speed planing hulls have complex hydrodynamic behaviors. The trim angle and drafts are very sensitive to speed and location of the center of gravity. Therefore, motion simulation for such vessels needs a strong coupling between rigid body motions and hydrodynamic analysis. In addition, free surface should be predicted with good accuracy for each time step. In this paper, velocity and pressure fields are coupled by use of the fractional step method. On the basis of integration of the two-phase viscous flow induced stresses over the hull, acting loads (forces and moments) are calculated. With the strategy of boundary-fitted body-attached mesh and calculation of 6-DoF motions in each time step, time history of ship motions including displacements, speeds and accelerations are evaluated. For the demonstration of the software capabilities, circular cylinder slamming is simulated as a simple type of water slamming. Then, a high-speed planing catamaran is investigated in the case of steady forward motion. All of the results are in good concordance with experimental data. The present method can be widely implemented in design as well as in performance prediction of high-speed vessels. 相似文献
4.
K. D. H. Bob-Manuel 《Ocean Engineering》2002,29(14):1841-1851
The prediction of capsize of small high-speed craft is highly complex. In this paper, risk analysis is applied to predict the probability of capsize of two types of high-speed craft due to dangerous wave events in the estuary of the Bonny River in the Niger Delta region of Nigeria. Fibreglass reinforced plastic (FRP) hull craft, widely used for transportation, were considered for the prediction. The probability of the craft encountering a dangerous wave situation at a random position at sea and the probability of capsize were calculated using published wave statistics and computer-based analytical models. Results obtained compared favourably with similar analyses carried out by previous investigators for other regions. Various rational and practical ways of reducing the probability of capsize to an acceptable level are presented. From the prediction it was established that human error was a predominant factor in the capsize of vessels. 相似文献
5.
The demand for high-speed craft (mainly catamarans) used as passenger vessel has increased significantly in the recent years. Looking towards the future and trying to respond to the increasing requirement, high-speed crafts international market is passing through deep changes. Different types of high-speed crafts are being used for passenger transport. However, catamarans and monohulls have been the main choice not only for passenger vessel but also as ferryboat.Generally speaking, the efficient hydrodynamic hull shapes, engine improvements, and lighter hull structures using aluminum and composite materials make possible the increase in cruising speed.The high demand for catamarans are due to its proven performance in calm waters, large deck area compared to monohull crafts and higher speed efficiency using less power. Although the advantages aforementioned, the performance of catamaran vessels in wave conditions still needs to be improved.The high-speed crafts (HSC) market is demanding different HSC designs and a wide range of dimensions focusing on lower resistance and power for higher speed. Therefore, the hull resistance optimization is a key element for a high-speed hull success.In addition to that, trade-off high-speed catamaran (HSCat) design has been improved to achieve main characteristics and hull geometry. This paper presents a contribution to HSCat preliminary design phase. The HSCat preliminary design problem is raised and one solution is attained by multiple criteria optimization technique.The mathematical model was developed considering: hull arrangement (area and volume), lightweight material application (aluminum hull), hull resistance evaluation (using a slender body theory), as well as wave interference effect between hulls, calculated with 3D theory application. Goal programming optimization system was applied to solve the HSCat preliminary design.Finally this paper includes an illustrative example showing the mathematical model and the optimization solution. An HSCat passenger inland transport in Amazon area preliminary design was used as case study. The problem is presented, the main constrains analyzed and the optimum solution shown. Trade off graphs was also included to highlight the mathematical model convergence process. 相似文献
6.
Osman Turan Zafer Ayaz Seref Aksu Jan Kanar Antoni Bednarek 《Ocean Engineering》2008,35(13):1339-1356
The study investigates the experimental and numerical analysis of the occurrence of auto-parametric rolling for large, high-speed pod-driven ships in waves. Considering unique design and performance targets, the aim here is to exploit susceptibility to auto-parametric rolling behaviour and to identify probable design and operational precautions. In order to achieve this aim, an existing non-linear time-domain software to simulate capsizing and other critical manoeuvring behaviours of slow- to medium-speed conventional and podded ships in waves is being enhanced for fast pod-driven vessels and then compared against the dedicated model test conducted in long-crested regular and random waves for a large, pod-driven containership model. This paper includes the presentation of current numerical modifications for pod-driven ships and the verification analysis. 相似文献
7.
This paper proposes a high-speed iterative procedure for estimating the ocean wave directional spectrum from vessel motion data. It uses as input data, the measurements from motion sensors that are commonly available on dynamically positioned vessels and which may easily be installed on any ship. Because the necessary sensors are relatively inexpensive or may already be installed, it becomes an ideal solution to provide initial estimates to offline estimation procedures and to give spectral updates under quickly changing weather conditions. The Kalman filtering algorithm, for iterative harmonic detection, and frequency domain vessel response data are used in the estimation procedure. The results and conclusions are still based on synthesized data, but very promising. 相似文献
8.
Prediction of ship motions at high Froude number is carried out using a time domain strip theory in which the unsteady hydrodynamic problem is treated in terms of the motion of fixed strips of the water as hull sections pass through it. The Green function solution is described and the integration of the ship motion carried out by an averaging method to ensure stability of the solution. The method is validated by comparison with tank data for conventional slender hulls suitable for catamarans, small water area twin hull (SWATH) forms and hulls suitable for high-speed monohulls. Motion computations are then carried out for 14 designs with an operating speed of 40 kts and a displacement of 1000 tonnes. The vessels are assumed not to be fitted with motion control systems for the purposes of this comparative study. Motion sickness incidence is predicted to rise to between 42 and 72% depending upon the hull design in 3 m head seas of average period 7.5 s. MSI values reduce in smaller seas with a shorter average period to be less than 15% in all cases in 1m seas with an average period of 5.5 s. 相似文献
9.
《Oceanic Engineering, IEEE Journal of》2006,31(2):421-431
This paper focuses on the mitigation of porpoising instability of high-speed planing vessels using controllable transom flap and dynamic feedback. A control oriented model that captures both steady-state and dynamic characteristics is presented and used to facilitate the model-based control design. A nonlinear controller is developed based on the feedback linearization method to achieve asymptotic stability of the planing boat, thus avoiding porpoising at high speeds. We first show that the full-state nonlinear dynamic model describing the ship motion is not feedback linearizable. A state transformation is then constructed to decompose the model into a linearizable subsystem and a nonlinear internal dynamic subsystem. A reduced order state feedback is shown next to stabilize the planing vessel motion around the equilibrium point. Analysis of the region of attraction is also performed to provide an assessment of the effective safe operating range around the equilibrium point. 相似文献
10.
Haruzo Eda 《Ocean Engineering》1980,7(3):379-397
Equations of yaw, sway, roll and rudder motions are formulated to represent realistic maneuvering behavior of high-speed ships such as destroyers. Important coupling terms between yaw, sway, roll and rudder were included on the basis of recent captive model test results of a high-speed ship. A series of computer runs was made by using equations of yaw, sway, roll and rudder motions. Results indicate substantial coupling effects between yaw, roll, and rudder, which introduce changes in maneuvering characteristics and reduce course stability in high-speed operation. These effects together with relatively small GM (which is typical for certain high-speed ships) produce large rolling motions in a seaway as frequently observed in actual operations. Results of digital simulations and captive model tests clearly indicate the major contributing factors to such excessive rolling motions at sea. 相似文献
11.
A planing hull is a marine vessel whose weight is mostly supported by hydrodynamic pressures at high-speed forward motion. Its high-speed character has made it popular and thus the interest for planing hulls for military, recreational and racing applications is progressively rising. The design and analysis procedure for high-speed planing hulls, due to their performance and speed requirements, is very important. Access to a fast, accurate technique for predicting the motion of these hulls plays a significant role in improvement in this field. Over the past several decades, numerous investigations have been done on hydrodynamic analysis of high-speed planing hulls. In this study, the existing techniques for analysis of these hulls are reviewed. Understanding the strengths and limitations of these techniques will help researchers and engineers select the most appropriate method for optimal design and analysis of a hull. To present a comprehensive study on the existing techniques, they are classified into two major categories: analytical–experimental and numerical techniques. The numerical techniques are further divided into methods for boundary value problems and domain-dependent problems. Each technique is applicable only for a limited range of cases. 相似文献
12.
Investigation of strategies to improve the recycling effectiveness of waste oil from fishing vessels
The marine ecological environment and fishery resources can be severely polluted or destroyed by waste oil from fishing vessels if they are emitted directly into the ocean without any proper pre-treatment process. International conventions such as MARPOL 73/78 regulate waste-oil emissions and require the installation of a waste oil–water separator only for ocean-going ships of over 400 gross tons. Hence, these international conventions are not applicable to most fishing ships due to their low gross tonnages. In addition, space on most fishing vessels is too limited to allow waste-oil storage tanks or a waste oil-water separator to comply with international maritime regulations. Because a significant amount of waste oil is produced by fishing vessels around the world every day, effective strategies or measures are needed to prevent this waste oil from polluting the marine environment. This study thus investigates strategies and measures for improving the effectiveness of waste-oil collection from fishing vessels. This study found that existing procedures for the collection and treatment of waste lubricating oil on land could be applied to the management of waste oil and bilge water from fishing vessels. Sufficient oil–water separators and storage facilities for the collection of waste oil should be placed at each fishing port and shipyard. Fishermen should then be required to deliver their waste oil to these storage facilities, from where it can be transported to legal recycling companies for further treatment. In addition, fishing harbor authorities should bear definitive responsibility for monitoring the illegal dumping of waste oil and for checking the waste-oil record books of fishing vessels. Each maritime country should enforce relevant laws and regulations to reduce the emission of waste oil from fishing vessels into the ocean. 相似文献
13.
14.
《Marine Policy》2015
Productivity change after transition to an individual transferable quota (ITQ) management system is driven by exit of some vessels, entry of other vessels, and changes in productivity of existing vessels. Generally, it is thought that an ITQ system boosts productivity due to the exit of less productive vessels. However, ITQ management systems also create an additional barrier to entry, and more productive vessels may not be able to enter the fishery. This study constructs the Färe–Primont index to measure productivity change for the Mid-Atlantic surf clam and ocean quahog fishery over a 32 year time period, which includes both pre and post-ITQ time periods. The index is then combined with a biomass change index to arrive at a measure of biomass adjusted productivity change. Results show that when biomass changes are considered, positive productivity gains occurred throughout the time period. Further examination of contributions from entering and survivor vessels show that entering vessels had little impact on aggregate productivity, but on an individual basis, they eventually were equal in productivity to survivor vessels. 相似文献
15.
基于AIS信息校准的双频地波雷达的船只融合跟踪 总被引：2，自引：0，他引：2
高频地波雷达（HFSWR）和自动船只确认系统（AIS）是船只跟踪的重要传感器。高频地波雷达可以用来跟踪探测区域的所有船只,而AIS只能用来确认合作船只的信息。由于海杂波的干扰,使用单频率地波雷达的船只跟踪会淹没在布拉格峰值的盲区里,改变探测频率是克服这一缺点的有效手段。在这种背景下,我们提出一种基于AIS校准的双频雷达融合探测算法。因为不同频率的地波雷达测量与AIS的测量值存在系统误差,所以AIS信息可以用来估计和校准地波雷达的每个频率的系统误差。首先,将合作目标的点迹测量与地波雷达的点迹测量通过JVC分配算法进行点迹关联。从合作船只的点迹关联结果中,双频雷达的系统误差可以估计和校准。其次,基于校准的双频雷达数据,使用融合JPDA-UKF算法进行船只跟踪。通过真实探测的数据的实验结果显示所提算法可以实时跟踪船只,相比单频率跟踪可以进一步提高跟踪能力和跟踪精度。 相似文献
16.
This paper investigates the inherent variability in the results of matched-field geoacoustic inversion algorithms. This algorithm-induced variability must be considered when interpreting inversion results in terms of environmental changes as a function of time or space. Fast simulated annealing (FSA), genetic algorithms (GA), and a hybrid algorithm (adaptive simplex simulated annealing; ASSA) are compared by performing multiple inversions of benchmark synthetic data (noise free and noisy) and acoustic data measured over both low- and high-speed sea-bed sediments in the MAPEX 2000 experiment. ASSA produced the lowest variability in inversion results for all cases, followed by GA and FSA. For the high-speed MAPEX 2000 case, the variability is essentially negligible, while for the low-speed case the variability is significant as compared with environmental variations reported in the literature. 相似文献
17.
A study of the seakeeping performance of a set of fishing vessels is carried out aiming to identify the seakeeping criteria, and vessel conditions that limit the operability of the fishing vessels in certain sea states. Ship motions and derived responses are obtained in fully developed sea states using the transfer functions of the hull forms. Those responses are assessed against the prescribed values, for the chosen criteria, to determine the vessels operational conditions that might result in hazards or seasickness. For the purpose of this study, each fishing vessel is considered operating in sea states 5 and 6, with different Froude numbers and heading angles, and their short term responses are assessed against the most relevant criteria related with the absolute and relative motions, accelerations, slamming and green water on deck. The results obtained show that roll and pitch criteria are most critical for seakeeping performance, and there is a significant influence of the transverse metacentric height, GMt, and the location of the reference checking points in the seakeeping performance of these fishing vessels. 相似文献
18.
Numerical and experimental study on hydrodynamic interaction of side-by-side moored multiple vessels 总被引：2，自引：0，他引：2
This paper aims to investigate the basic interaction characteristics of side-by-side moored vessels both numerically and experimentally. A higher-order boundary element method (HOBEM) combined with generalized mode approach is applied to analysis of motion and drift force of side-by-side moored multiple vessels (LNG FPSO, LNGC and shuttle tankers). Model tests were carried out for the same floating bodies investigated in the numerical study in regular and irregular waves. Global and local motion responses and drift forces of three vessels are compared with those of calculations. Discussions is highlighted on applicability of numerical method to prediction of sophisticated multi-body interaction problem of which motion behavior is very important to analysis of mooring dynamics of deep sea floating bodies. 相似文献
19.
20.
Many disastrous oil spill accidents from damaged vessels become worse especially when the early treatment is not prompt enough. To properly handle this type of accidents and prevent further disasters, International Maritime Organization establishes and imposes various rules and regulations. Better understanding of the propulsive performance of damaged vessels is important for containing the oil spill while the vessels are being towed or self-propelled. In the present study, both experimental and computational methods were used to investigate the flow phenomena around the hull and the hydrodynamic performances of a VLCC in various damaged conditions. From the resistance and self-propulsion test results, it is found that higher power is required to propel the ship especially with the bow trim. Wake measurement data provide physical insight into the factors to be considered for the propeller operation in damaged conditions. 相似文献