Initiation of motion and scour burial of objects underwater
Initiation of motion and scour burial of objects underwater
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DOI：
10.1016/j.oceaneng.2016.12.029
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发表时间：
2017-02-01
影响因子：
5
通讯作者：
Friedrichs, Carl T.
中科院分区：
文献类型：
--
作者：
Renni, Sarah E.;Brandt, Alan;Friedrichs, Carl T.
进行了实验室实验，以检查物体的移动和掩埋，包括在刚性底部的运动开始，冲刷掩埋在沙床中，冲刷和运动开始实验之间的相互作用涵盖了与未爆弹药移动性相关的一系列物体直径与底部粗糙度比(D/k)。结果表明，圆柱体在水流和波浪作用下的临界导纳参数Theta(Ucrit)近似为Theta 6(D/k)(-72)。对于加速流动，还提出了对该关系式的修正。冲刷试验得出了UXO的平衡埋深(BEQ)与沉积物屏蔽层参数(Sd)的函数关系的公式，其形式为B-eq/D=a(2)Theta sed(B2)。对于水流诱导的活床冲刷，相对较大的圆柱体(D>；8厘米)导致a(2)和b(2)接近0.36。较小的圆柱体(D<；3厘米)和锥形更容易掩埋(a(2)接近15，b(2)接近1.1)。还给出了包含附加长度标度的BEQ的一种基于物理的替代关系。对于加速流动的沙子上的物体，观察到其行为是冲刷掩埋和当前达到临界移动性的速度之间的竞争。结果表明，通过将移动时刻的坑深作为有效的底部粗糙度，可以得到运动开始的一般解释。
Laboratory experiments were conducted to examine mobility and burial of objects, including onset of motion on a rigid bottom, scour burial into a sand bed, and the interplay between scour and motion onset Experiments covered a range of object diameter-to-bottom roughness ratios (D/k) of relevance to mobility of unexploded ordnance (UXO). Results indicate that the critical mobility parameter (Theta(Ucrit) approximate to varies as Theta 6(D/k)(-72) for cylinders under currents and waves. Modifications of this relation are also presented for accelerating flows. Scour experiments produced formulae for the equilibrium burial depth (Beq) for UXO as a function of the sediment Shields parameter (Theta(sed)) of the form B-eq/D = a(2) Theta sed(b2). For current-induced live-bed scour, relatively large cylinders (D > 8 cm) result in a(2) and b(2) approximate to 0.36. Smaller cylinders (D < 3 cm) and a tapered shape bury more easily (a(2) approximate to 15 and b(2)approximate to 1.1). An alternate, physics based relation for Beq incorporating additional length scales is also presented. For objects on mobile sand under accelerating flow, behavior was observed to be a contest between scour burial and the current speed reaching critical mobility. It is shown that by considering pit depth at the moment of mobility to be the effective bottom roughness, a general explanation of the onset of motion can be obtained.