The comparative hydrodynamics of rapid rotation by predatory appendages

Countless aquatic animals rotate appendages through the water, yet fluid forces are typically modeled with translational motion. To elucidate the hydrodynamics of rotation, we analyzed the raptorial appendages of mantis shrimp (Stomatopoda) using a combination of flume experiments, mathematical modeling and phylogenetic comparative analyses. We found that computationally efficient blade-element models offered an accurate first-order approximation of drag, when compared with a more elaborate computational fluid-dynamic model. Taking advantage of this efficiency, we compared the hydrodynamics of the raptorial appendage in different species, including a newly measured spearing species, Coronis scolopendra. The ultrafast appendages of a smasher species (Odontodactylus scyllarus) were an order of magnitude smaller, yet experienced values of drag-induced torque similar to those of a spearing species (Lysiosquillina maculata). The dactyl, a stabbing segment that can be opened at the distal end...

无数水生动物通过旋转附肢在水中运动，但学界通常仅基于平动运动对流体作用力进行建模。为阐明旋转运动的流体动力学机制，我们结合水槽实验、数学建模与系统发育比较分析，对螳螂虾（口足目，Stomatopoda）的掠食性附肢开展了研究。研究发现，相较于更为精细的计算流体动力学模型，计算效率较高的叶素模型（blade-element models）可对阻力提供精准的一阶近似结果。依托这一计算优势，我们对不同物种的掠食性附肢流体动力学特性进行了对比分析，其中包括新测定的穿刺型物种Coronis scolopendra。粉碎型物种Odontodactylus scyllarus的超高速附肢尺寸较穿刺型物种小一个数量级，但其所受的阻力矩与穿刺型物种Lysiosquillina maculata的阻力矩相近。作为位于远端可展开的穿刺节段，其指节（dactyl）……