Department of Civil Engineering Sciences and Architecture, Polytechnic University of Bari, 70125 Bari, Italy.
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853, USA.
Phys Rev Lett. 2019 Aug 2;123(5):058501. doi: 10.1103/PhysRevLett.123.058501.
We describe a new mechanism that produces bedforms and characterize the conditions under which it operates. The mechanism is associated with pressure gradients generated in a fluid saturated particle bed by a plate oscillating in the water above it. These vertical pressure gradients cause oscillatory bed failure. This facilitates particle displacement in its interior and transport at and near its surface that contribute to the formation of a heap under the plate. Flows over erodible beds generally cause shear stresses on the bed and these induce bed failure. Failure driven by pressure gradients is different from this. We report on bedforms in a bed of glass beads associated with such fluctuating pressure gradients. We measure the development of the profiles of heaps as a function of time and determine the tangential and normal motion of areas on the beds surface and estimate the depth of penetration of the tangential transport. The measurements compare favorably with a simple model that describes the onset of failure due to oscillations in pressure.
我们描述了一种产生床形的新机制，并描述了其运行的条件。该机制与在其上方的水中振动的板在饱和颗粒床中产生的压力梯度有关。这些垂直压力梯度导致床的振动破坏。这促进了颗粒在内部的位移以及在其表面和附近的输运，从而有助于在板下形成堆。在可侵蚀床面上的流动通常会在床面上产生剪切应力，这些剪切应力会导致床面破坏。由压力梯度驱动的破坏与这种破坏不同。我们报告了与这种脉动压力梯度相关的玻璃珠床的床形。我们测量了随着时间的推移堆的轮廓的发展，并确定了床表面上区域的切向和法向运动，并估计了切向输运的穿透深度。测量结果与描述由于压力振动而导致破坏的开始的简单模型吻合良好。
