Saline currents (SCs) have commonly been used to model muddy turbidity currents (TCs) in a laboratory. However, little is known about the limitations of this proxying, in particular when concerning processes and products related to their sedimentologic and stratigraphic imprints. The present study is aimed at investigating experimental hydraulic and sedimentological conditions and processes involved in the generation and development of bedforms by both SCs and TCs, when similar input conditions are applied (discharge, slope, densimetric Froude number). In all performed runs reported herein, only ripples were observed to form, and were identified and classified using known criteria such as their dimensions, near-bed shear stresses (⁠⁠), shear velocities (⁠⁠), and grain Reynolds values (Re*). Turbidity currents were observed to deposit sediments carried by the flow predominantly in the upstream section of the flume, increasing bed slope and thus increasing ⁠, ⁠, and near-bed concentrations (cb). This resulted in longer-wavelength bedforms compared to those generated by SCs under similar input conditions in those sections of the flume. On the other hand, along the downstream sections of the flume, bed slopes were observed to remain similar for all experiments, and both types of currents showed similar vertical distribution of velocities, concentrations, and stable stratification. Measured bedform wavelengths and heights were slightly higher when generated by SCs, due to the coarser bed material observed in SCs (which influenced the increase in near-bed turbulent intensities). Moreover, TCs presented a slight decrease in turbulence intensities due to their observed high near-bed suspended-sediment concentration. Spatial and temporal changes in several hydraulic parameters in both SCs and TCs highlight the role of sediment suspension in modifying turbulent processes and vertical stratification of these flows, depending on their concentrations. Both hydraulic and sedimentologic observations of this study support in principle the assumption that SCs can be used experimentally as a surrogate for diluted TCs to reproduce bedforms classified as ripples, as long as both type of currents reach similar hydraulic and sediment-transport conditions, in particular for depth-averaged concentration Cvol < 1% and near-bed concentration cb < 2%.

中文翻译：

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使用实验浊度流和盐水流形成波纹的比较水力和沉积学研究

盐水流 (SCs) 通常用于在实验室中模拟浑浊流 (TCs)。然而，人们对这种代理的局限性知之甚少，特别是在涉及与其沉积学和地层印记相关的过程和产品时。本研究旨在研究当应用相似的输入条件（流量、坡度、密度弗劳德数）时，SCs 和 TCs 形成和发展床型所涉及的实验性水力和沉积学条件和过程。在本文报告的所有执行运行中，仅观察到波纹形成，并使用已知标准进行识别和分类，例如其尺寸、近床剪切应力 (⁠⁠)、剪切速度 (⁠⁠) 和晶粒雷诺值 (Re *)。观察到浊流主要在水槽的上游部分沉积由水流携带的沉积物，增加了河床坡度，从而增加了 ⁠、⁠ 和近床浓度（cb）。与水槽的这些部分中类似输入条件下 SCs 产生的床形相比，这导致更长的波长床形。另一方面，沿着水槽的下游部分，观察到所有实验的河床坡度保持相似，两种类型的水流显示出相似的速度垂直分布、浓度和稳定的分层。由于在 SCs 中观察到的较粗糙的床层物质（这影响了近床湍流强度的增加），当由 SCs 生成时，测量的床形波长和高度略高。而且，由于观测到的高近床悬浮沉积物浓度，TCs 的湍流强度略有下降。SC 和 TC 中几个水力参数的时空变化突出了沉积物悬浮在改变湍流过程和这些流动的垂直分层中的作用，这取决于它们的浓度。本研究的水力和沉积学观察原则上都支持这样的假设，即只要两种类型的水流达到相似的水力和沉积物输送条件，SCs 就可以在实验上用作稀释 TCs 的替代物，以再现被归类为波纹的床型。对于深度平均浓度 Cvol < 1% 和近床浓度 cb < 2%。SC 和 TC 中几个水力参数的时空变化突出了沉积物悬浮在改变湍流过程和这些流动的垂直分层中的作用，这取决于它们的浓度。本研究的水力和沉积学观察原则上都支持这样的假设，即只要两种类型的水流达到相似的水力和沉积物输送条件，SCs 就可以在实验上用作稀释 TCs 的替代物，以再现被归类为波纹的床型。对于深度平均浓度 Cvol < 1% 和近床浓度 cb < 2%。SC 和 TC 中几个水力参数的时空变化突出了沉积物悬浮在改变湍流过程和这些流动的垂直分层中的作用，这取决于它们的浓度。本研究的水力和沉积学观察原则上都支持这样的假设，即只要两种类型的水流达到相似的水力和沉积物输送条件，SCs 就可以在实验上用作稀释 TCs 的替代物，以再现被归类为波纹的床型。对于深度平均浓度 Cvol < 1% 和近床浓度 cb < 2%。