Nordstrom K N, Dorsch D S, Losert W, Winter A G
Institute for Physical Science and Technology, and Department of Physics, University of Maryland, College Park, Maryland, USA.
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Oct;92(4):042204. doi: 10.1103/PhysRevE.92.042204. Epub 2015 Oct 22.
RoboClam is a burrowing technology inspired by Ensis directus, the Atlantic razor clam. Atlantic razor clams should only be strong enough to dig a few centimeters into the soil, yet they burrow to over 70 cm. The animal uses a clever trick to achieve this: by contracting its body, it agitates and locally fluidizes the soil, reducing the drag and energetic cost of burrowing. RoboClam technology, which is based on the digging mechanics of razor clams, may be valuable for subsea applications that could benefit from efficient burrowing, such as anchoring, mine detonation, and cable laying. We directly visualize the movement of soil grains during the contraction of RoboClam, using a novel index-matching technique along with particle tracking. We show that the size of the failure zone around contracting RoboClam can be theoretically predicted from the substrate and pore fluid properties, provided that the timescale of contraction is sufficiently large. We also show that the nonaffine motions of the grains are a small fraction of the motion within the fluidized zone, affirming the relevance of a continuum model for this system, even though the grain size is comparable to the size of RoboClam.
“机器人蛤”是一种受大西洋剃刀蛤（学名：Ensis directus）启发的挖掘技术。大西洋剃刀蛤自身的力量仅够在土壤中挖几厘米深，但它们却能钻到70多厘米深。这种动物运用了一个巧妙的方法来实现这一点：通过收缩身体，它搅动并局部液化土壤，从而降低挖掘时的阻力和能量消耗。基于剃刀蛤挖掘机制的“机器人蛤”技术，对于那些能从高效挖掘中受益的海底应用可能具有重要价值，比如锚固、水雷引爆和电缆铺设。我们运用一种新颖的折射率匹配技术并结合粒子跟踪，直接观察了“机器人蛤”收缩过程中土壤颗粒的运动。我们发现，只要收缩的时间尺度足够大，收缩的“机器人蛤”周围破坏区的大小可以根据基质和孔隙流体特性从理论上进行预测。我们还表明，颗粒的非仿射运动在液化区内的运动中只占一小部分，这证实了对于该系统而言连续介质模型的适用性，尽管颗粒大小与“机器人蛤”的尺寸相当。
