共查询到20条相似文献，搜索用时 359 毫秒
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This paper reports experimental measurements of the hydrodynamics forces acting on a low drag submersible. The model was manufactured using standard, cost-effective methods without undue attention paid to the roughness or waviness of the model's surface. It was seen, using flow visualisation techniques, that the laminar boundary layer extended over 70% of the vehicle length; furthermore, no separation of the flow was seen over the remaining 30% of the body. Hydrodynamic forces were measured, and a significant reduction in drag was found compared with standard turbulent submersible shapes. The low drag performance was quite resilient to changes in incidence, showing a large drag “bucket” for angles of incidence between ± 4°. With the addition of a set of cruciform fins at the rear of the body, incorporating control surfaces, it was found that for a centre of gravity position forward of 41.3% of the body length, the vehicle would be statically stable both stick-free and stick-fixed. Finally, using a pitot tube wake rake the velocity profile of the boundary layer at the propeller location was found to be that of an attached, turbulent boundary layer closely matching a
power law. The importance of full interference measurement tests to allow for the support strut effects is clearly demonstrated. 相似文献
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The boundary-element method has been widely used as a design tool in the offshore and ship building industry for more than 30 years. Its application to wave energy conversion is, however, more recent. This paper deals with the numerical modelling of a free-floating sloped wave energy device. The power take-off mechanism of the device consists of an immersed tube with a piston sliding inside. The modelling is done using the boundary-element method package WAMIT. The model is first worked out for the case where the axis of the tube is vertical. It is then derived for the tube inclined and successfully verified against numerical benchmark data. A companion paper presents results of a detailed comparison with a physical model study. 相似文献
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Phase control may substantially increase the power absorption in point-absorber wave energy converters. This study deals with validation of dynamic models and latching control algorithms for an oscillating water column (OWC) inside a fixed vertical tube of small circular cross-section by small-scale testing. The paper describes experimental and numerical results for the system's dynamics, using simple and practical latching control techniques that do not require the prediction of waves or wave forces, and which will be relevant to any type of point-absorbing devices.In the experimental set-up, the upper end of the tube was equipped with an outlet duct and a shut-off valve, which could be controlled to give a latching of the inner free surface movement. The pressure drop through the open valve is used as a simplified measure of the energy extraction. The control was realized by using the real-time measurement signals for the inner and outer surface displacement.A mathematical model of the system was established and applied in numerical simulation. In the case the OWC's diameter is much smaller than the wavelength and the wave amplitude much smaller than the draft, the free surface movement inside the tube can be described as an oscillating weightless piston. For this hydrodynamic problem an analytical solution is known. In addition, the mathematical model includes the effects of viscous flow losses, the air compressibility inside the chamber and the pressure drop across the valve. Experimental results were used to calibrate some of the model parameters, and the total model was formulated as a coupled system of six non-linear, first-order differential equations. Time-domain integration was used to simulate the system in order to test the control strategies and compare with experimental results. 相似文献
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首次将PIV技术应用于测试偏心环空幂律流体紊流螺旋流速度场，设计了一套可调偏心度的垂直环空管道实验装置。实验为不同浓度的聚丙烯酰胺水溶液在偏心度分别为40％和80％的垂直环空管道内做螺旋流动的PIV实验。得到了轴向速度影响规律：压力梯度一定时，黏滞性的减小或内管转速的增加将使轴向速度增大；流量一定时，黏滞性的减小或内管转速的增加都将使宽间隙处紊流核心区的轴向速度减小；偏心度的增大可以使紊流核心区轴向速度减小；当其它条件相同时，轴向速度随着压力梯度或流量的增加而增大。PIV实验结果与PHOENICS数模结果吻合良好。证明了PIV技术对幂律流体偏心环空螺旋流速度场进行测试是可行的、有效的。 相似文献
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Robert E. Salomon 《Ocean Engineering》1989,16(3)
A device for converting ocean wave energy into electricity utilizing a rocking buoy and a hydrogen pressure cell is described. The moored buoy contains a pneumatic tube filled with a dense liquid which rocks back and forth as a result of the ocean wave activity. Hydrogen gas, maintained above the dense fluid is alternatively compressed and expanded by the moving fluid. The hydrogen gas communicates with a hydrogen pressure cell and the resulting pressure difference across the cell leads to an electrical voltage and under load, to electrical power. 相似文献
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This paper presents a procedure to calculate the design pressure distributions on the hull of a wave energy converter (WEC). Design pressures are the maximum pressure values that the device is expected to experience during its operational life time. The procedure is applied to the prototype under development by Martifer Energy (FLOW—Future Life in Ocean Waves).A boundary integral method is used to solve the hydrodynamic problem. The hydrodynamic pressures are combined with the hydrostatic ones and the internal pressures of the large ballast tanks. The first step consists of validating the numerical results of motions by comparison with measured experimental data obtained with a scaled model of the WEC. The numerical model is tuned by adjusting the damping of the device rotational motions and the equivalent damping and stiffness of the power take-off system. The pressure distributions are calculated for all irregular sea states representative of the Portuguese Pilot Zone where the prototype will be installed and a long term distribution method is used to calculate the expected maximum pressures on the hull corresponding to the 100-year return period. 相似文献
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This note presents some analytical results for a tail–tube buoy configuration frequently used in wave energy conversion. The overall approach is based on Falnes and McIver's (Falnes, J., McIver, P., 1985. Surface wave interactions with systems of oscillating bodies and pressure distributions. Applied Ocean Research 7 (4), 225–234) extension to floating oscillating water columns of Evans' (Evans, D.V., 1982. Wave power absorbtion by systems of oscillating surface pressure distributions. Journal of Fluid Mechanics 114, 481–499) theory of oscillating pressure distributions. The diffraction air-flow flux through the tube and the diffraction wave force on the flotation collar are obtained using the formulation of Garrett (1970, 1971) (Garrett, C.J.R., 1970. Bottomless harbours. Journal of Fluid Mechanics 43 (3), 433–449. Garrett, C.J.R., 1971. Wave forces on a circular dock. Journal of Fluid Mechanics 46 (1), 129–139). Results can be used in sizing the tube and collar for efficient energy conversion. 相似文献
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The technique of geotextile tubes used to construct dikes for land reclamation has been widely used. The tubes are usually filled with slun＇y of soil, such as sand, silt or clay. The tensile stress developed in the geotextile during filling the tube is the dominant factor for construction of a safe dike. The existing design methods are good for designing sausage shaped tubes and can not be directly applied for designing fiat tubes, which are commonly used in dike construction. This paper presents a procedure that can detenmine the relatiorrship among the tube size, the pumping pressure, the unit weight of the slurry, and the tensile stress developed in the geotextile during the tube filing. When the tubes are piling up to form the dike, the tubes in the bottom will sustain the load from the weight of the upper ones. A procedure is also developed to calculate the changes of the mechanical and geometrical behavior of the tubes under the load with a similar method. All these approaches have been programmed, which can help dike designers to select the suitable geotextile and determine the profile of the dike. 相似文献
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A high-reliability, dual-mode release has been used on untethered, mid-water vehicles successfully since 1970. This device is operated by electrical signal or by hydrostatic pressure. A second release which is self-contained and includes a relocation pinger has been designed for precisely timed release at minimum cost. The release function in this device occurs after the preset time by electrical corrosion of a wire link. This release has been used to recover sedimen trap arrays. 相似文献
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负温度系数(negative temperature coefficient,NTC)热敏电阻器由于在窄温区内具有极高的灵敏度,在海洋领域中有着广泛的应用,但深海应用中固有的高静水压力,对器件的测温准确度造成不利影响。为了更好地认识这种现象,以珠状NTC热敏电阻器为研究对象,利用海洋环境高压模拟装置,开展了静水压力作用对器件电学特性影响的研究,固定环境温度25℃和0℃,压力范围0~60 MPa,步长5 MPa。结果显示,随着静水压力的增大,NTC热敏电阻器的电阻值减小;环境温度25℃和0℃时,5~60 MPa的静水压力造成的漂移分别为-0.11%~-2.81%、-0.19%~-2.78%,等效于温度漂移分别为0.024~0.624℃、0.036~0.535℃。这为热敏电阻器在深海温度准确测量的提升提供了指引,有利于在海洋测温领域中更好的应用。 相似文献
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Accumulator-Based Deep-Sea Microbe Gastight Sampling Technique 总被引：1，自引：0，他引：1
1.IntroductionPlenty of microbes exist in deep sea(Jiang,2000).They can survive and propagate under theconditions of extraordinary cold or heat and high pressure(Liu,2001).Studies on deep-sea microbesshowthat they have the function of decomposing petroleu… 相似文献
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采用高效液相色谱-蒸发光散射(HPLC-ELSD)法建立了刺参皂苷的特征图谱.方法:色谱柱为Symmetry C18(150 mm×4.6 mm,5 μm),采用0.2% 乙酸水溶液-乙腈进行梯度洗脱,流速1.0 mL/min;柱温30 ℃;漂移管温度70 ℃;载气压力25 psi.结论:方法具有良好的专属性,可以作为刺参类产品是否含有刺参皂苷的评价方法. 相似文献
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深海超高压环境模拟试验装置是深海关键技术与装备研究中必不可少的测试装置。采用传统的一体式压力筒研制大直径、超高压试验装置时难以克服应力集中的问题,安全性较低且造价昂贵。采用预应力钢丝缠绕技术研制的深海超高压环境模拟试验装置克服了其局限性,该装置是目前国内工作压力最高、可实现筒内环境数据监测且升降压自动控制的压力试验装置。文中简要介绍了该装置的系统组成及研制过程中主要关键技术问题及解决方法,最后介绍了典型实验应用,为深海超高压环境模拟试验装置的研制与应用提供参考。 相似文献
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A Bianchi J Garcin O Tholosan 《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(12):2129
A high-pressure serial sampler (HPSS) has been developed to obtain microbial activity data unbiased by decompression during retrieval with the same frequency as used for the measurement of other hydrological parameters. We fitted a commercially available multisampling device with eight pressure-retaining vessels. This device allows the collection of eight 500 ml samples of undecompressed water during the same hydrocast to a depth of 3500 m. The HPSS includes a CTD; therefore the eight sampling depths can be selected using the conventional hydrological parameters. During the retrieval and the incubation period pressure conditions of each sampler are permanently recorded on the surface computer. Incubation is in a temperature-controlled water bath to keep the samples in the natural temperature conditions. During the incubation period, several sub-samples may be successively collected without pressure loss within the culture vessel, allowing time-course experiments. During a stratified period, comparison of microbial production rates simultaneously measured on the decompressed and undecompressed seawater samples collected between 850 and 2000 m depth showed that the deep-sea bacteria were affected by decompression during retrieval. 相似文献
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Liu Zhihong Huang Yuying Liu Qikai Doctor Candidate Dept. of Mechanics Huazhong University of Science Technology 《中国海洋工程》1993,(3)
Based on the beam system model used by Chater, Hutchinson and Neale (1982), the recovery behavior of propagating buckle on elastic structures is first found out from the computational results. As the representative of some elastic structures, the Chater-Hutchinson-Neale model indicates that once the buckle meets arresters, unlike the case in submarine pipelines, it will be reflected back to continue its propagation in a negative phase or a negative direction. The pressure which maintains the negative propagation, however, is as same as that required for the positive propagation. This fact has been examined in the experiment of the bulge propagation on a long elastic latex tube. The present discovery greatly supports the hypothesis that the buckle propagation coresponds to the coexisting phase of structures. 相似文献