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1.
Remote measurements of the spatial mean ocean wind speeds were obtained using Doppler spectra resolved to 0.08 Hz from high-resolution HF skywave-radar backscatter measurements of the ocean surface. A standard deviation of 2.4 m/s resulted from the correlation of observed winds over the ocean and the broadening of the Doppler spectra in the vicinity of the higher first-order Bragg line. This broadening, for Doppler spectra unperturbed by the ionospheric propagation, is proportional to the increase in power caused by higher order hydrodynamic and electromagnetic effects in the vicinity of the Bragg line and inversely proportional to the square root of the radio frequency. A lower bound on the measure of wind speed was established at 5 m/s by the low resolution spectral processing and low second-order power. An upper limit is suggested by the steep slope in the region of the sea backscatter spectrum outside the square root of two times the first-order Bragg line Doppler. 相似文献
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A wave-height meter using a simple microwave Doppler radar,simeq10 mW in power and 10.525 GHz in frequency, is proposed so that we can measure oceanic waves effectively while the ship is steaming. It was first applied to the measurement of the variation of water level generated in a wave tank, which suggested that it is adequately applicable to the measurement of oceanic waves. A field test was carried out off the cape of Nojimazaki by installing the Doppler radar 5 m above the sea level at the bow of the ship. The result agreed reasonably well with that measured simultaneously by the ultrasonic wave-height meter installed at the same position. Another test is running successfully on a larger ship with the wave-height meter installed at 9 m above the sea level. The significant wave height measured by the present meter is being compared with that observed visually by the navigation officers. 相似文献
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Ship detection with high-resolution HF skywave radar 总被引：2，自引：0，他引：2
This paper presents an overview of ship detection by high-frequency (HF) skywave backscatter over-the-horizon radar (OTHR). Ships have been detected at ranges of 2000 km or more by OTHR that uses sufficient resolution in the radar spatial and Doppler frequency domains. The HF sea-echo Doppler spectrum limits the target signal-to-clutter ratio (SCR), as a function of the ocean wave-height distribution, wind direction, radio frequency, and ship target radial velocity. Maximum sea-clutter spectrum purity, and hence larger SCR, is achieved with the use of stable single-mode ionospheric propagation. Real-time measurement and interpretation of ionospheric propagation features therefore must guide the choice of OTHR operating frequency. Experimental data recorded at the ONR/SR1 Wide Aperture Research Facility (WARF) bistatic OTHR in central California demonstrate reliable ship detection in the Northeast Pacific Ocean. WARF transmits 1-MW average effective radiated power, using a linear frequency-modulated continuous-wave (FMCW) waveform, and receives with a 2.55-km broadside array of vertical monopole element pairs. Swept bandwidths as high as 200 kHz have been used. Sufficient spectral resolution is achieved with a coherent integration time (CIT) of 12.8 s. Longer CIT, and autoregressive (AR) spectral analysis techniques such as Marple's algorithm, have been used to improve Doppler resolution. 相似文献
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利用小波包分析和混沌特征提取进行船舶辐射噪声分类 总被引：3，自引：2，他引：3
基于船舶辐射噪声信号具有非线性、非平稳的特征，提出采用提取船舶辐射噪声信号的非线性混沌特征量和多尺度小波能量特征，并将两者综合作为特征参数输入神经网络分类器进行船舶分类识别。实验结果表明，该方法能较好地区分不同类型的船舶。 相似文献
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The work describes an inversion algorithm for HF radar measurement of nondirectional wave spectra using an omnidirectional receive/transmit antenna. Such a radar would be suitable for deployment on a stationary ship or drill rig. In this approach, wave information is extracted from the radar observations by numerically inverting the integral equation representing the backscatter return from the ocean. Test results of this technique applied to data collected using a 25.4-MHz radar installed on a ship have been very positive. For the two measurements collected, there is a high degree of correlation between the radar wave estimates and those of a WAVE-TRACK buoy 相似文献
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A software detection model has been developed to predict the returned Doppler spectrum for an iceberg target for ground-wave Doppler radars. This software model is based on proposed new estimates for the backscattered Doppler-dependent iceberg cross section for assumed iceberg models, as well as the backscattered Doppler spectrum from the ocean surface. The model includes estimates for forward and reverse transmission losses, based on classical spherical earth derivations. In addition, the transmission losses account for the effects of surface roughness through a modified surface impedance. Standard estimates for man-made and atmospheric noise have been considered in the detection model. A comparison between the results predicted by the detection model and data acquired during an experiment conducted at Byron Bay, Labrador, Canada has been effected. The hardware used for the experiment was an HF Doppler radar operating at 25.40 MHz. The transmitting antenna was a three-element Yagi array and the receiving antenna a 24-element narrow-beam linear array. By using iceberg ground truthing information the Doppler spectrum for individual icebergs was predicted using the software model. The predicted spectra were compared with the received spectra on a target signal-to-noise power ratio basis. The results of this comparison give a degree of confidence to the detection model and show that ground-wave radars are effective ice hazard remote sensors. 相似文献
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In this paper the joint density of waveheight and half-wavelength is considered for waves observed at a fixed time point and encountering waves that are overtaking a ship from behind. The densities for these two cases are related by a Doppler shift, expressed in terms of the relative velocity of the waves and the ship. Based on this observation, an approximation of the encountered density is proposed. This approximation is then investigated for a Gaussian sea having a Pierson–Moskowitz spectrum. 相似文献
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《海洋技术学报》2024,(1)
作为当今世界上最先进的测流仪器，水平式声学多普勒流速剖面仪（Horizontal Acoustic Doppler Current Profiler，H-ADCP） 因其精度高、速度快等突出优势在河流中的应用越来越广泛，但在航运业发达地区，由于受船行波的影响，很难得到稳定可靠的流速数据，阻碍了H-ADCP在平原河网地区的应用和推广。目前技术上很难做到完全消除船行波的影响，本文将H-ADCP应用在平原河网地区对流速进行测量，并分析了船行波对测量精度的影响。从H-ADCP设备选型、测量和安装方式、测量预处理、数据后处理等多方面入手，可以有效消减船行波对H-ADCP 的影响，从而提高测流精度。同时，通过实验测量断面一天内平均流速变化情况，得到受船行波影响后的流速波形，然后采用数据处理手段，验证了所提方法的可行性。 相似文献
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为提高母型船阻力性能,以船体阻力性能为优化对象,基于改造母型船法,研究船舶球鼻艏以及船尾线型的改变对船舶阻力性能的影响.采用高度集成化的Tribon系统、可视化绘图软件Auto CAD及CFD(Computational Fluid Dynamics)通用前处理软件ICEM联合建模的方法来建立船体模型.通过模拟计算结果与实验值的对比分析,验证CFD技术在船舶阻力性能预报中的合理性和有效性.通过对比3种不同球鼻艏时的船体阻力得知:从阻力性能方面考虑,对于低速丰满型船舶选用普通型球鼻艏以及中高速船舶采用上翘型球鼻艏均可以获取较好地减阻效果.同时比较不同航速下尾部线型对船体总阻力的影响表明,选优后的方形尾在相同的航速下阻力低、消耗的功率小、形状效应小、黏压阻力和摩擦阻力也相对较小. 相似文献
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Several important statistical properties of the HF sea echo and its Doppler power spectrum, which are useful in optimizing the design of radar oceanographic experiments, are established. First- and second-order theories show that the echo signal (e.g., the voltage) should be Gaussian; this is confirmed with experimental surface-wave data i) by comparison of the normalized standard deviation of the power spectrum at a given frequency with its predicted value of unity, and ii) by cumulative distribution plots of measured spectral amplitudes on Rayleigh probability charts. The normalized standard deviation of the dominant absolute peak amplitudes of the power spectrum (which wander slightly in frequency) are shown from experimental data to besim 0.7 for the first-order peaks andsim 0.5 for the second-order peaks. The autocorrelation coefficient of the power spectra is derived from measured data and interpreted in terms of the spectral peak widths; from this information, the correlation time (or time between independent power spectrum samples) iS shown to besim 25-50 s for radar frequencies above 7 MHz. All of these statistical quantities are observed to be independent of sea state, scattering cell size, and relatively independent of radar operating frequency. These quantities are then used to establish the statistical error (and confidence interval) for radar remote sensing of sea state, and it is shown, for example, that 14 power spectral samples result in a sample average whose rms error about the true mean is 1.0 dB. 相似文献
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V. G. Bondur N. N. Filatov Yu. V. Grebenyuk Yu. S. Dolotov R. E. Zdorovennov M. P. Petrov M. N. Tsidilina 《Oceanology》2007,47(6):769-787
This paper presents the main results of processing the data obtained in the study of hydrophysical processes during multidisciplinary monitoring of the anthropogenic impact on the coastal basin of Mamala Bay (Oahu Island, Hawaii). The results of the hydrophysical measurements carried out in August–September of 2002–2004 using stationary moorings and dropped and towed ship sensors were analyzed as the initial data. On the basis of these measurements, spatiotemporal, statistical, and spectral characteristics of different hydrophysical parameters of the marine envrionement in the basin of Mamala Bay were calculated, including three-dimensional components of the velocity vectors, the spectra of different components of velocities, the spectra of temperature fluctuations, and the characteristics of internal waves. The variability of the temperature fields and the correlation of the tidal phenomena with the temperature measurements and fluctuations caused by internal waves were analyzed. The materials and methods of the oceanographic studies and the results of the analysis of the meteorological and hydrological conditions are presented. The results obtained are used for a multidisciplinary analysis of the satellite and sea truth data. 相似文献
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This is a Part II of a paper of nonlinearities of wind waves in the deep open ocean. As shown in Part I, bound waves in deep sea are detectable by extracting secondorder Doppler spectra from the Doppler spectra of HF (high-frequency) radio waves scattered from the sea surface. There is a remarkable agreement between the calculated and measured Doppler spectra, considering the noise levels in measured Doppler spectra and the uncertainties in directional properties. The theoretical expression for bound waves is thus verified. Furthermore, the upper limit in calculating the Doppler spectra for the second-order approximation is presented from field observations, although we cannot conclude that it is equivalent to the limitation of the second-order bound wave theory. It is shown that analysis of radio wave scattering by the sea surface is one useful means of understanding the nonlinear properties of ocean waves. 相似文献
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提出了一种新型综合发电船,其主要由驳船、波浪能转换装置、风能转换装置、太阳能转换装置和其余发电相关设施五个部分组成;本装置基于驳船这一可移动载体,能够根据实时能源情况更改工作场地,是一个可移动的分布式能源供应系统,它能够综合利用选定区域内的波浪能、风能和太阳能进行发电,解决现有海上能源发电系统存在的发电效率低、稳定性差和单元发电成本高等问题。文中详细阐述了该发电装置的结构和工作原理,并从设计、运用等方面浅析了该发电装置的优点。这种综合发电船具有较大的推广性和实用性。 相似文献
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在SAR与AIS联合探测探测舰船目标实验中,通过对2010-11-05T06：51渤海海峡Radarsat-2影像的和与之时空匹配的AIS数据比较,发现2种手段探测到的静止的舰船目标能够精确的匹配,但是运动的舰船目标存在一定的偏差.分析了偏差产生的原因,其中距离向偏差是由时间误差引起的;方位向偏差主要是由多普勒频移造成的;这与运动舰船目标的航速、航向及SAR与AIS的探测时间误差有关.在此基础上建立了数学模型,分析上述参数对偏差的影响,并对偏差加以修正,从而实现了SAR与AIS探测结果的匹配. 相似文献
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Acoustic Doppler backscattering techniques have been exploited for measuring water velocity for nearly 40 years. Although most early applications centered on measuring ship speed, much work has been done during the last 20 years to adapt the techniques to measure oceanic velocity fields. The purpose of this paper is to summarize the work that has been done and to discuss the state of acoustic Doppler technology. 相似文献
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The paper discusses spectra of the radiance coefficient of the sea surface measured in the open ocean and in coastal waters, and different kinds of these spectra corresponding to the water types are revealed. The focus is the method of measuring the radiance coefficient from a moving ship with a hyperspectral spectrophotometer. The results of studying a water area of Russia’s Black Sea coast at river mouths are presented. A new calibration method that can process measurement results taking into account the impact of cloudiness and wind has been proposed and tested. The concentrations of the main admixtures in natural seawater in the studied water area are estimated according to the obtained spectra; these estimates are compared to the results of direct analysis of water samples. It has been shown that the method of remote measurement of the sea radiance coefficient from on board a ship makes it possible to obtain operative maps of the spatial distribution of the main seawater admixtures. 相似文献
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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
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Gao Xiangfan Liang Xianguang Jiang Niandong Feng Manzhi Wang Wei Senior Engineer Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou
Associate Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou
Engineer Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 《中国海洋工程》1992,(3)
This paper presents the test of a ship model for the design of a backward-bent duct oscillating water column type wave energy conversion system, to supply electric power for a light ship. This system suggests a new way to produce electric power automatically for large light ships. 相似文献