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《海洋预报》2015,(5)
为了研究海洋锋对声传播的影响,借鉴黑潮引起的台湾海峡南部海洋锋的历史水文观测资料,提出并建立了适合描述台湾海峡南部海洋锋的数学模型及其声速表达式。通过与实测资料对比,建立的海洋锋模型能准确反映客观实际情况,表现出较好的效果。同时,在借鉴了前人研究经验的基础上,采用Argo实测资料,建立了台湾海峡南部海洋锋的数学模型及其声速表达式,利用MMPE水下声场模型进行了海洋声场数值模拟试验,对目标海区典型的声场结构进行了声线路径模拟和传播损失的计算仿真,并将实验结果通过与前人进行的实际大洋声场实验的结果比较,证实了本文的模拟结果是准确可信的,提高了水声数值模拟试验的准确有效性。 相似文献
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由于表面声道与深海声道间的耦合效应,声波在双轴海洋声道中的传播比较复杂,因此求解双轴海洋声道中的声场就比较困难。在 WKBZ 本征函数的基础上,推导出了参考界面相位修正的一致表达式,并将浅海声传播的波束位移射线简正波(BDRM)理论应用于计算双轴海洋声道中的声场,进行了数值模拟并与传统简正波方法进行比较,结果表明应用 BDRM 理论计算的传播损失具有很高的精度和速度,可以对双轴海洋声道内声传播问题进行分析和预报。 相似文献
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内孤立波对海洋平台的安全运行存在一定的威胁,基于三维数值水槽对内孤立波传播引起的半潜平台受力及其周围流场的分布进行了数值模拟研究.通过与试验对比,分析了入射波幅和分层流体深度比对半潜平台上内孤立波荷载特性的影响规律,验证了数值模拟结果是准确可靠的.研究表明,内孤立波引起的平台荷载会随着内孤立波波幅的增加而增大,随着分层流体深度比的增加而减小.基于对平台周围剖面速度场和三维涡场的演化规律研究,发现在内孤立波传播过程中,平台周围会出现明显的速度减小区,平台周围会有大量的漩涡产生并发生脱落现象. 相似文献
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浅海中的平滑平均声场 总被引：14，自引：0，他引：14
浅海声传播问题虽然已进行过许多研究,但由于浅海声场往往包含大量简正波或射线,形成复杂的空间干涉结构,计算起来十分困难.实践表明,由于海洋环境与实验条件的不稳定性,使复杂的干涉结构很难与实验相吻合.有时实验点落在图1所示的理论曲线附近就认为是理论与实验基本一致,而不能验证曲线的精细结构.这种情况下人们就考虑用比较简便的方法计算声场的空间平滑结构,以避免繁琐的数值计算. 相似文献
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三维极限波的产生方法及特性 总被引：9，自引：2，他引：9
极限破碎波浪是造成海洋结构物破坏的主要因素之一,对极限波浪的产生方法和特性进行研究具有重要的工程意义.利用长波传播快、短波传播慢的原理,从理论上给出了产生三维极限波的方法,利用基于Boussinesq方程的数值模拟对该方法进行了验证,同时研究了中心频率、频率宽度和频谱形式等对极限波浪特性的影响,为该方法的进一步应用提出了建议. 相似文献
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东海黑潮锋作为中国近海的一类特殊海洋学现象,对水声传播产生的复杂影响已受到关注,但对其影响机制的认识还较为欠缺.应用BELLHOP水声学数值模型分析了典型东海黑潮锋环境下的声场特性,结果表明:穿过锋面时声线干涉伴随的声能强弱空间分布出现明显偏移,同时波导中泄漏的声能对锋面非均匀环境引起的传播损失进行了补偿,使波导区域之外的声能变化小于5dB(声波频率为1 kHz).相比之下,从外海暖水混合层向近海传播时表面声道的瓦解可使传播损失突然增大10 ～ 15 dB(声波频率为1 kHz).东海黑潮锋环境下的声场能量异常分布体现了海底地形和水文环境的共同影响,地形条件对声场样式起支配性作用,而锋面引起的非均匀水文环境则是使声能空间分布出现异常变化的关键调制性因素. 相似文献
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《中国海洋大学学报(自然科学版)》2015,(11)
基于简正波理论的波导不变量在声传播特性描述中已得到广泛应用,而当环境与距离无关或存在轻微扰动时,基于射线理论的声场特性可以用一个新的物理量—射线稳定性参数来描述。本文通过简正波干涉声场数值模拟,通过分析简正波相长干涉形成的能量包传播路径与射线传播路径相互关系,利用简正波水平干涉结构距离上的周期性与射线水平跨距相等的特点,采用简洁方式证明了射线稳定性参数与简正波波导不变量间的等价性,从而在射线和简正波理论中建立了一个新的联系。对远距离射线模型声传播仿真结果的分析表明,与射线传播时间相比,射线稳定性参数作为射线理论的一个新的参数,可有效用于描述声传播特性,并能够反映海洋环境变化,应用于海洋环境参数声学反演。 相似文献
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Numerical calculation of acoustic field perturbation expressions can be used to predict fluctuations after propagation through ocean sound-speed structures, but before the onset of multipath. The general form of the expressions for signal spectra or correlation functions allow numerical evaluation for an unlimited quantity of vector wave-number spectral models of refractive index. In order to help define the bounds of applicability of the theory, log-intensity fluctuation variances have been calculated for three major situations: ocean internal waves, ocean turbulence, and continuous strong large-scale turbulence. Propagation through ocean thermocline internal waves, realistically weak thermocline turbulence, and unrealistically strong turbulence show that scintillations of intensity can be predicted and understood to first order up to ranges of tens of kilometers, given the proper transmission geometry. Internal wave effects dominate over any effects from expected microstructure. Nonhorizontal transmission yields small fluctuations, but eventually refractive effects of the sound channel will contribute some additional spatial variability and multipath, complicating the use of the theory. Multipath due to the sound channel can exist at ranges where the random small-scale structures would contribute only small perturbations (no multipath from small structures) 相似文献
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Modal Wave Number Tomography for South China Sea Front 总被引：10，自引：0，他引：10
1 .IntroductionTheSouthChinaSealiestothesoutheastpartoftheChinesecontinent.TheKuroshioflowsbytheeastsideoftheLuzonStraitfromsouthtonorthinwinter ,spring ,andautumn .TheKuroshioaf fectsnearcurrentfieldsandtemperaturefields,changingtheoceanenvironmentparametersandsoundpropagation .Thus ,theoceanacoustictomographytechniqueisofpotentialtolong term ,largescalemonitoringoftheocean .Themodalwavenumbertomographymethod (Rajanetal.,1 987;Frisketal.,1 989)isusedtoobtainthesoundspeedprofileinwatercol… 相似文献
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A modal (full-wave) method has been developed to predict ocean sound speed profiles from propagated acoustic field data. The method assumes a point source of sound in the ocean and uses as data the values of the transmitted acoustic field at an array. The formalism for depth-dependent sound speeds consists of the standard Hankel integral transform of the depth solution. In the travel length coordinate, the latter is written exactly, using the Green's function, in terms of an integral equation whose kernel includes the sound speed profile correction. A Born approximation to this equation is used. This is just the WKB solution, and permits the use of a nontrivial input (or guess) profile, here chosen as bilinear. The use of asymptotic methods enables us to write the data as an integral transform over the profile correction. The transform can be inverted. An example is presented for full-bandwidth inversion. 相似文献
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QIU Xiaofang PENG Linhui WANG Ning ZHU Jianxiang 《中国海洋工程》2001,(4):589-596
The modal wave number tomography approach is used to obtain sound speed profile of water column in deep ocean. The approach consists of estimation of the local modal eigenvalues from complex pressure field and use of these data as input to modal perturbative inversion method for obtaining the local sound speed profile. The empirical orthonormal function (EOF) is applied to reduce the parameter search space. The ocean environment used for numerical simulations includes the Munk profile as the unperturbed background speed profile and a weak Gaussian eddy as the sound speed profile perturbation. The results of numerical simulations show the method is capable of monitoring the oceanic interior structure. 相似文献
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海底对浅海声传播的影响很大。海底有复杂的多层结构。在计算声场时如果把多层海底的影响都考虑进去,就会使计算复杂化,得不出一个清晰的物理图象。因此,在计算中往往使用海底反射损失系数来代替多层海底的模型。但海底反射损失与角度有复杂的依赖关系。为了计算方便,提出过不少简化模型。已经使用的模型有反射损失与角度无关、与角度一次方成正比;后来又提出反射损失在某一临界角之下与角度一次方成正比,在临界角之上与角度无关的三参数模型,克服了远场与近场衔接的问题[1,2]。但这些模型不一定在所有情况下都能反映海底反射损失与角度的关系的主要特征。本文提出一个近似方法,可以计算海底反射损失按任意规律随角度单调上升的情况下的声场。 相似文献
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海洋声速剖面严重影响着水下声传播特性,近实时地获取声速剖面对水下声通信、水下定位、鱼群探测等都有重要意义。单经验正交函数回归（single Empirical Orthogonal Function regression,sEOF-r）方法通过建立声速剖面的经验正交系数与海面遥感数据之间的线性回归关系来反演声速剖面。但是,海洋是一个复杂的动力系统,声速与海面遥感数据并不是简单的线性关系,因此,本文基于Argo历史网格数据,通过自组织映射（Self-Organizing Map,SOM）生成海平面高度异常（Sea Level Anomaly,SLA）、海表面温度（Sea Surface Temperature,SST）等海表遥感数据以及表层声速仪测量的表层声速与声速剖面异常之间的非线性映射;然后利用近实时的海表遥感数据和表层声速反演三维海洋声速场。声速剖面反演的结果表明,在多源信息融合的优势下,本文方法的反演性能最稳定且精度最高,声速剖面的平均反演精度比经典sEOF-r方法提高约2 m/s,比未考虑表层声速的经典SOM方法提高约1 m/s。 相似文献
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Reciprocal travel-time data along acoustic multipaths between transceivers in the ocean sound channel can be inverted to form estimates of sound speed and horizontal current in the vertical plane of the transceiver pair. We investigate the quality of such estimates in a range-independent environment. Since most of the information gathered along an acoustic path is concentrated near its turning depths, inversions are characterized by strong sidelobe contamination. Estimates at depths in the upper ocean are contaminated by fields in the lower ocean and vice versa. Therefore estimates can be improved by use of a priori knowledge of contaminating fields at the position of the sidelobe. The Backus-Gilbert method is adapted to allow for use of a priori knowledge and three measures of system performance are defined, viz., resolution length, stochastic error, and ratio of sidelobe to primary lobe acceptance. Trade-off relations among these quantities are calculated for 17 eigenrays in a Munk canonical profile for various orders of a priori knowledge. The limit of perfect knowledge gives an absolute bound on system performance. Numerical examples indicate poor performance in the lower ocean; but good estimates of sound speed and acceptable estimates of horizontal current are feasible in the upper ocean. 相似文献
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Matched-fieId inversion (MFI) undertakes to estimate the geometric and geoacoustic parameters in an ocean acoustic scenario by matching acoustic field data recorded at hydrophone array with numerical calculations of the field. The model which provides the best fit to the data is the estimate of the actual experimental scenario. MFI provides a comparatively inexpensive method for estimating ocean bottom parameters over an extensive area. The basic components of the inversion process are a sound propagation model and matching (minimization) algorithm. Since a typical MFI problem requires a large number of computationally intensive sound propagation calculations, both of these components have to be efficient. In this study, a hybrid inversion algorithm which uses a parabolic equation propagation model and combines the downhill simplex algorithm with genetic algorithms is introduced. The algorithm is demonstrated on synthetic range-dependent shallow-water data generated using the parabolic equation propagation model. The performance for estimating the model parameters is compared for realistic signal-to-noise ratios in the synthetic data 相似文献
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The ocean acoustic tomographic (OAT) approach to sound speed field estimation is generalized to include a variety of sources of information of interest such as an oceanographic model of the sound speed field, direct local sound speed measurements, and a full field acoustic propagation model as well as measurements. The inverse problem is presented as a four-dimensional field estimation problem using a variational approach commonly used in oceanographic data assimilation. The current OAT approach is shown to be a special case of the general framework. The matched-field tomography (MFT) approach is also discussed within this context. A simple implementation of this novel approach is then investigated in the absence of a suitable oceanographic model, and acoustic propagation is accounted for using a standard parabolic equation model. The inverse equations derived are validated numerically through a simple inversion example, and some issues on environmental mismatch and computations are discussed. The developments then provide a basic framework for ongoing data-model melding in acoustically focused oceanographic sampling (AFOS) network 相似文献
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在分析海洋环境标量场要素数据特点,了解常规的海洋环境要素分析和可视化表达方式的基础上,对在三维球体模型上实现海洋标量场要素时空分析和可视化表达的方法和技术进行了研究.提出了海洋标量场要素数据的三维空间数据模型,以此为基础利用VC与Open GL技术实现纹理数据的实时绘制,并采用基于对象的方法在三维球体上对其进行可视化表达,实现了真正意义上基于地球球体模型的海洋标量场要素的可视化.该基于球体的可视化方式能更好地表现研究对象的区域特点,特别是在进行大范围区域乃至全球性研究时更具优势.同时,通过按需进行数据抽取,系统在数据加载效率与数据承载总量上都有所提高,在＂数字海洋＂原型系统中目前已经加载了全球范围多个精度的温度、盐度、密度、声速等标量场数据,并实现了业务化运行. 相似文献