Mean Flow and Turbulence Structure of Sediment‐Laden Gravity Currents: New Insights using Ultrasonic Doppler Velocity Profiling
Mean Flow and Turbulence Structure of Sediment‐Laden Gravity Currents: New Insights using Ultrasonic Doppler Velocity Profiling
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充满沉积物的重力流的平均流动和湍流结构：使用超声波多普勒速度剖面的新见解
DOI：
10.1002/9781444304275.ch12
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发表时间：
2009
影响因子：
2.4
通讯作者：
J. Peakall
中科院分区：
文献类型：
--
作者：
J. Best;A. Kirkbride;J. Peakall
利用超声多普勒速度廓线(UDVP)对含沙重力流的平均结构和湍流结构进行了定量研究。UDVP既可以测量不透明流体中的速度，也可以整体重建一维流场。本章介绍了在含沙重力流中首次使用UDVP的结果，结果表明：(I)正向流中的速度最大值位于床面上方约0.3的头部高度；(Ii)正向流速度最大的区域与水流中最低的湍流强度有关；(Iii)最高的湍流强度既与近床面切变有关，也与头部背面的混合有关；(Iv)由地形反射产生的回流，以不同类型的孔洞形式，可以完全用UDVP来量化；(5)与头部有关的湍流尺度似乎与头部高度相同，(6)过去对重力流的研究不得不使用含盐溶液和无泥沙弥散来代替含沙水流，在许多方面都是低密度、含沙重力流的良好替代品。UDVP的未来应用为研究一系列含沙水流中的湍流、泥沙输移和沉积之间的相互作用带来了巨大的希望，包括传统测量技术难以或不可能应用的水流。
The mean and turbulent structure of a sediment‐laden gravity current is quantified using ultrasonic Doppler velocity profiling (UDVP). UDVP allows both measurements of velocities in opaque fluids and holistic reconstruction of the one‐dimensional flow field. This chapter presents results from the first use of UDVP in a sediment‐laden gravity current that illustrate: (i) the velocity maximum in the forward flow lies at approximately 0.3 of the head height above the bed; (ii) the region of the velocity maximum of the forward flow is associated with the lowest turbulence intensities within the current; (iii) the highest turbulence intensities are associated with both near‐bed shear and mixing on the back of the head; (iv) return flows created by reflection from topography, in the form of different types of bore, may be fully quantified by UDVP; (v) the scale of turbulence associated with the head appears to be of the same order as the head height, and (vi) past studies of gravity currents that have had to use saline solutions and sediment‐free dispersions as a proxy for sediment‐laden currents, are in many aspects a good substitute for low‐density, sediment‐bearing gravity currents. Future use of UDVP holds great promise for study of the interaction between turbulence, sediment transport and deposition in a range of sediment‐laden flows, including flows where conventional measurement techniques are difficult or impossible to apply.