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首页> 外文期刊>Marine Geology >Estimation of high-resolution sediment concentration profiles in bottom boundary layer using pulse-coherent acoustic Doppler current profilers
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Estimation of high-resolution sediment concentration profiles in bottom boundary layer using pulse-coherent acoustic Doppler current profilers

机译：使用脉冲相干声多普勒电流剖面仪估算底部边界层中的高分辨率泥沙浓度剖面

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摘要

The capability of two acoustic profilers — SonTek's 1.5-MHz pulse-coherent acoustic Doppler profiler (PC-ADP) and RDI's 600-kHz acoustic Doppler current profiler (ADCP) with pulse-coherent mode — was evaluated for estimating high-resolution suspended sediment concentration (SSC) profiles in bottom boundary layer. In the laboratorymeasurementswith a PC-ADP, two types of sedimentswere tested to study acoustic responses to grain size. A natural sediment sample from Clay Bank, a mixture of clay and very fine sand, showed a good linear relationship between range-corrected volume scattering (S_v ) and backscattered strength (E) until SSC increased up to about 10 gl~(-1). In contrast, a commercially available kaolinite exhibited earlier signal saturation and nonunified linear regressions between S_v and E, most likely because the particle size is much smaller than the transmitted acousticwavelength. Using a pulse-coherent ADCP, the field measurement results from Mobile Bay, Alabama showed that the acoustically-derived SSC profiles were well matched with the optically-derived outcomes although slight discrepancieswere noted. The overestimation of acoustically-derived SSC near the bed may be related to the side lobe interferencenear the bed and the enhanced acoustic sensitivity by coarser particles and denser aggregates eroded fromthe bed. Mean absolute error of acoustic estimateswas within 4.1–7.3% of the optically-derived SSC range, which is attributable to the different acoustic and optical scattering responses to given sediment size spectra. Despite someerror sources in acoustic inversion, the results fromlaboratory and field experiments suggest that the pulse-coherent acoustic profiler is able to reveal the evolution of in-situ near-bed SSC profiles with high vertical and temporal resolutions.
机译：为了评估高分辨率悬浮泥沙浓度，评估了两个声学剖面仪的性能— SonTek的1.5MHz脉冲相干声学多普勒剖面仪（PC-ADP）和RDI的脉冲相干模式的600kHz声学多普勒电流剖面仪（ADCP）。 （SSC）轮廓位于底部边界层。在使用PC-ADP进行的实验室测量中，测试了两种类型的沉积物以研究对晶粒尺寸的声学响应。来自粘土银行的天然沉积物样品（由粘土和非常细的沙子组成的混合物）显示出范围校正的体积散射（S_v）和反向散射强度（E）之间的良好线性关系，直到SSC增加到大约10 gl〜（-1） 。相反，可商购的高岭石表现出较早的信号饱和度和S_v与E之间的非统一线性回归，这很可能是因为粒径远小于透射声波波长。使用脉冲相干ADCP，来自阿拉巴马州莫比尔湾的现场测量结果表明，尽管注意到了微小差异，但声源SSC轮廓与光学源结果非常匹配。床附近对声源SSC的高估可能与床附近的旁瓣干扰以及从床中侵蚀出来的较粗颗粒和较密集的聚集体增强的声学灵敏度有关。声学估算的平均绝对误差在光学衍生SSC范围的4.1–7.3％之内，这归因于对给定沉积物尺寸谱的不同声学和光学散射响应。尽管声学反演中存在一些误差源，但实验室和现场实验的结果表明，脉冲相干声学剖面仪能够揭示具有高垂直和时间分辨率的原位近床SSC剖面的演变。

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