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1.
On the basis of the little clause in the “Outline Specification” for a new ship: “Trial speed at a load draught of … with the engine at maximum continuous rating has to be …” some aspects regarding propulsion of single-screw ships are discussed, especially the problem of how to combine the hull form, the propeller and the machinery for propulsion in such a way that an optimal solution is obtained.In order to limit the problem, only ships provided with a single conventional propeller for propulsion are considered.A parameter study of a single-screw vessel has been done in order to get some concrete information on the interaction between ship, engine and propeller, and to investigate how the ship propeller power curve should be placed in relation to the engine operation area and to investigate changes in this relationship when the conditions change. 相似文献
2.
In terms of the nonlinear characteristics of hydraulic propulsion system used in 3500 m rated work-class ROV (remotely operated underwater vehicle), the paper improved the responsiveness of the hydraulic propulsion system by adding an impulse signal to the input end of the system. Because the maximum static damping moment provided from water is much larger than the dynamic damping moment, it results in large dead zone of thrust during the startup process of the hydraulic propulsion system. The dead zone of thrust caused by static damping moment can be effectively reduced by adding a specific impulse signal to the input end of the propulsion system. The results of numerical simulations and underwater experiments show that using this method, the nonlinear characteristics of the hydraulic propulsion system have been significantly improved. 相似文献
3.
摆动尾鳍水动力性能的试验和数值研究 总被引：1，自引：0，他引：1
鱼类能够在水下高速度、低噪音、高效率地游动。鱼类出色的推进性能通过其摆动尾鳍实现。这种摆动尾鳍推进方式已经用在了水下无人航行器上。因此研究摆动尾鳍的水动力性能是非常有意义的。对摆动尾鳍的推进水动力性能进行了详尽的研究。设计、装配了一套仿尾鳍推进系统,并对其进行了相应的水动力试验。在试验中研究了运动参数对摆动尾鳍水动力性能的影响。与此同时,采用基于雷诺平均N-S方程的数值方法对摆动尾鳍的水动力性能进行了研究。在数值计算中采用了k-ωSST湍流模型和有限体积法。数值计算结果和水动力试验结果进行了比较。对尾鳍表面的压力分布和流场中的尾涡结构进行了分析。水动力试验和数值计算都表明摆动尾鳍可以产生推进力和较高的推进效率。 相似文献
4.
The present paper describes results of the experimental investigation of a small-scale mono-hull model boat propelled by a localised flexural wave propagating along the plate of finite width forming the boat's keel. Forward propulsion of the boat was achieved through flexural wave propagation in the opposite direction, which is similar to the aquatic propulsion used in nature by stingrays. The model boat under consideration underwent a series of tests both in a Perspex water tank and in an experimental pool. In particular, the forward velocity of the boat has been measured for different frequencies and amplitudes of the flexural wave. The highest velocity achieved was 32 cm/s. The thrust and propulsive efficiency have been measured as well. The obtained value of the propulsive efficiency in the optimum regime was 51%. This indicates that the efficiency of this type of aquatic propulsion is comparable to that of dolphins and sharks (around 75%) and to that of a traditional propeller (around 70%). In contrast with a propeller though, the wave-like aquatic propulsion has the following advantages: it does not generate underwater noise and it is safe for people and marine animals. 相似文献
5.
Correlations between the optical characteristics of Lake Baikal waters and relations of optical characteristics with the content of suspended matter and chlorophyll in waters of the lake have been found. The formulas obtained for Lake Baikal waters have been compared with similar formulas of relations in other water basins. 相似文献
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7.
Research on Design Method of the Full Form Ship with Minimum Thrust Deduction Factor 总被引：1，自引：1，他引：0
In the preliminary design stage of the full form ships, in order to obtain a hull form with low resistance and maximum propulsion efficiency, an optimization design program for a full form ship with the minimum thrust deduction factor has been developed, which combined the potential flow theory and boundary layer theory with the optimization technique. In the optimization process, the Sequential Unconstrained Minimization Technique(SUMT) interior point method of Nonlinear Programming(NLP) was proposed with the minimum thrust deduction factor as the objective function. An appropriate displacement is a basic constraint condition, and the boundary layer separation is an additional one. The parameters of the hull form modification function are used as design variables. At last, the numerical optimization example for lines of after-body of 50000 DWT product oil tanker was provided, which indicated that the propulsion efficiency was improved distinctly by this optimal design method. 相似文献
8.
Boris S. Krumgalz 《Marine Chemistry》1989,27(3-4)
The solubilities of halite in Dead Sea waters and in their mixtures with Mediterranean Sea waters were estimated using Pitzer's equations. The calculated halite saturation for Dead Sea waters sampled at various occasions during 1979–1983 is in good agreement with the naturally observed phenomenon of halite deposition at this time. A halite saturation curve for mixtures of Dead Sea and Mediterranean Sea waters has been obtained and permits the prediction of halite deposition in these mixtures on evaporation. 相似文献
9.
针对十万吨级深远海养殖工船在波浪中的阻力和运动响应开展了船模试验与模拟计算,并对其最小推进功率进行了校核。以试验流体力学（EFD）模型试验与模型尺度计算流体力学（CFD）模拟计算的结果进行对比作为方法验证,将实尺度CFD模拟计算的结果直接用于最小推进功率的校核。结果显示,EFD模型试验结果与模型尺度CFD计算结果误差在10%左右,计算精度满足工程要求。在规定的恶劣海况下该船型波浪增阻占总阻力的比例最高可达56.3%,螺旋桨转矩可达最大转矩的63.9%。等级2简化评估法得到的最小推进功率为等级1线评估法给出的最小功率线值的58.9%。研究表明实尺度CFD模拟计算可直接用于船舶最小推进功率的校核,此深远海养殖工船使用等级2简化评估方法进行校核更容易满足规范要求,其最小推进功率应不小于6 833 kW。 相似文献
10.
The hydrodynamic performance of a hybrid CRP pod propulsion system was studied by RANS method with SST turbulence model and sliding mesh. The effect of axial spacing on the hydrodynamic performance of the hybrid CRP pod propulsion system was investigated numerically and experimentally. It shows that RANS with the sliding mesh method and SST turbulence model predicts accurately the hydrodynamic performance of the hybrid CRP pod propulsion system. The axial spacing has little influence on the hydrodynamic performance of the forward propeller, but great influence on that of the pod unit. Thrust coefficient of the pod unit declines with the increase of the axial spacing, but the trend becomes weaker, and the decreasing amplitude at the lower advance coefficient is larger than that at the higher advance coefficient. The thrust coefficient and open water efficiency of the hybrid CRP pod propulsion system decrease with the increase of the axial spacing, while the torque coefficient keeps almost constant. On this basis, the design principle of axial spacing of the hybrid CRP pod propulsion system was proposed. 相似文献
11.
波浪滑翔机直接利用波浪能实现大范围长距离的机动运动观测,在海洋环境观测中可以发挥重要的作用。本文对波浪滑翔机推进装置在启动阶段的翼片的水动力学行为进行了研究。以波浪滑翔机水下推进装置的翼片为研究对象,运用雷诺平均Navier-Stokes方程(RANS),对给定垂荡和摆动运动的翼片水动力学进行了水动力分析和仿真,模拟了单个翼片、纵向阵列多翼片的运动状况,得到推进装置翼片附近的压力分布和整体推进动力,分析翼片间距变化在启动阶段对推进力的影响作用。通过该研究工作为深入理解波浪滑翔机推进装置工作状态提供了理论依据。 相似文献
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A new sledge net system using propulsion vehicles has been developed to sample more efficiently the demersal juveniles of marine organisms. A net attached to a sledge maneuvered by a SCUBA diver who uses operating switches on a steering handle to adjust the altitude of the sledge and the position of the tickler chains to ensure that the footcloth of the mouth of the net remains in constant contact with the bottom surface. Video camera, flow meter, compass, and dive computers are positioned on the sledge net in the view of the diver. Given that the system can attain speeds of 70 cm s−1, the net can be employed to capture highly mobile fish. Unlike most boat-based net sampling methods, the use of propulsion vehicles means that there are no sound or vibration disturbances due to the boat and tow ropes typically used to maneuver these types of sampling nets. Marine fauna was collected at monthly intervals over a two-year period in a sampling area along the southern coast of Hokkaido, Japan. A total of 2641 specimens comprising 61 species and including five species which were the first records for the region were collected. These findings suggest that the new sledge net system employing propulsion vehicles was effective for sampling demersal juveniles, particularly in situations where sledge nets towed by boats or push nets cannot be deployed. 相似文献
14.
本文介绍了浅海海洋质子磁力仪在胶州湾中的试验结果,解决了浅海海洋质子磁力仪在实验室中未能解决的几个问题,已成功地应用于整个胶州湾的浅海海洋磁场测量中,首次获得了近岸浅海湾的完整海洋磁场资料。 相似文献
15.
中国近海藻毒素及有毒微藻产毒原因种调查研究进展 总被引：2，自引：0，他引：2
麻痹性贝类毒素在我国近海污染问题已十分突出,基本呈现逐年加剧的趋势。20世纪90年代,南海麻痹性贝类毒素污染较重; 21世纪初,北黄海麻痹性贝类毒素污染较重;近几年,渤海和福建近海麻痹性贝类毒素污染较重;可产生麻痹性贝类毒素的微藻有亚历山大藻和裸甲藻等。采用小鼠生物法检测我国近海腹泻性贝类毒素超标率32%左右,采用液相色谱/质谱法检测,仅有3起超标的研究报道;现行小鼠生物法检测腹泻性贝类毒素假阳性问题十分突出,应尽快废除;腹泻性贝类毒素均是脂溶性的,脂溶性海洋生物毒素在我国近海常年可检出,偶有虾夷扇贝毒素和鳍藻毒素超标现象。可产生脂溶性毒素微藻有鳍藻和原甲藻及网状原角藻等。失忆性贝类毒素在我国近海常有检出,但无超标现象;产毒微藻有拟菱形藻等。西加鱼毒素在我国南海污染较重,但毒素标准物质的匮乏,限制了西加鱼毒素的调查研究;至今尚未确定产生西加鱼毒素的微藻。酶联免疫吸附法和液相色谱串联质谱法相结合已成为藻毒素快速准确检测成熟的技术,逐渐代替小鼠生物法和液相色谱法。 相似文献
16.
Whitings (patches of suspended fine-grained calcium carbonate) on the Great Bahama Bank (GBB) have been studied since the 1940s. The source and cause of these whitings have been hotly debated for a number of years. Recent studies have shown that resuspension of underlying sediments act as seed crystals for the slow precipitation of CaCO3. Similar studies have not been conducted on the nearby more northerly Little Bahama Bank (LBB) where satellite photographs indicate the presence of extensive whitings north of the Grand Bahama Island. Research cruises were made to the LBB in July 2003 and May 2005. On board measurements were used to examine the distribution of the components of the carbonic acid system in LBB waters. The distribution of suspended calcium carbonate was also determined and samples of the suspended material and underlying sediments were collected for analyses, including 14C age determinations.The maximum residence time for waters on the LBB is a little over half (～ 144 d) that on the GBB. A ～ 20% decrease was found in the salinity-normalized titration alkalinity for inner bank waters. This yields a carbonate precipitation rate similar to waters on the GBB. However, unlike the waters in the whitings on the GBB where no changes in carbonic acid system parameters have been detected, large changes in the carbonic acid system parameters were found in the whiting waters of the LBB. These results clearly indicate that active precipitation was occurring in these waters. These observations are interpreted as indicating that there is a much slower mixing of waters associated with whitings and surrounding bank waters on the LBB than on the GBB. The more closed nature of whitings on the LBB makes them better targets for study of the processes taking place in whitings.Suspended carbonate mineralogy and geochemistry closely matched those of the fine-grained portion of the underlying sediments. These results support a close relationship between carbonates found in whitings and those in underlying sediments. This is further evidenced by a similar age for whiting carbonates (～ 700 y) and easily resuspended sediment carbonates (～ 1000 y) and is what was previously observed on the GBB.These observations indicate that the processes leading to whiting formation and associated calcium carbonate precipitation along with changes in water chemistry are quite similar in these two shallow carbonate bank environments in the Bahamas. 相似文献
17.
根据１９８５－１９８７年来１９８９－１９９１年对青海湖及其水系的考查资料，研究其化学变化。结果表明，近３０年来，青海湖及其入湖河流水系在萎缩过程中，水系总矿化度增加，逐渐咸化。除尕海水的Ｍｇ＾２＋；耳海水的Ｋ＾＋，ＳＯ＾２－４，ＣＯ３＾２－；人湖河流水的ＳＯ４＾２－离子浓度减小外，青海湖、尕海及耳海本中Ｎａ＾＋，Ｃｌ＾－，ＳＯ４＾２－离子增加速率较大，Ｃａ＾２＋，Ｍｇ＾２＋等离子增加速率较小。尕海 相似文献
18.
The data of SeaWiFS (Sea-Viewing Wide Field-of-View Sensor), installed on SeaStar, has been used to generate SSC (suspended sediment concentration) of complex and turbid coastal waters in China. In view of the problems of the SeaDAS (SeaWiFS Data Analysis System) algorithm applied to China coastal waters, a new atmospheric correction algorithm is discussed, developed, and used for the SSC of East China coastal waters. The advantages of the new algorithm are described through the comparison of the restdts from different algorithms. 相似文献
19.
A growing interest has been devoted to the contra-rotating propellers (CRPs) due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R & D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers. 相似文献
20.
Resistance and propulsion characteristics of various commercial ships based on CFD results 总被引：2，自引：0，他引：2
This paper uses computational tools to examine the speed performance of various types of commercial ships including resistance and propulsion characteristics. Eight commercial ships built in the last decade were selected for the study. They include four large-sized container carriers, one bulk carrier, one VLCC, and two LNG carriers. The Reynolds averaged Navier-Stokes equation has been utilized, and the computations were executed under the same conditions of the model tests to predict the speed performance, i.e., resistance and self-propulsion. The self-propulsion point was obtained from load-varying tests. The speed performance was predicted based on the model-ship performance analysis method of the revised ITTC’78 method. The limiting streamlines on the hull, wave characteristics around the model ship, and the wake characteristics on the propeller plane were also investigated. After completing the computations, a series of model tests were conducted to evaluate the accuracy of the computational predictions. The predictions clearly reveal the differences in the resistance and propulsion characteristics regarding the various types of commercial ships, and may be applicable to hull-form design. 相似文献