Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
J Exp Biol. 2012 Mar 1;215(Pt 5):785-95. doi: 10.1242/jeb.063040.
It has long been suspected that the denticles on shark skin reduce hydrodynamic drag during locomotion, and a number of man-made materials have been produced that purport to use shark-skin-like surface roughness to reduce drag during swimming. But no studies to date have tested these claims of drag reduction under dynamic and controlled conditions in which the swimming speed and hydrodynamics of shark skin and skin-like materials can be quantitatively compared with those of controls lacking surface ornamentation or with surfaces in different orientations. We use a flapping foil robotic device that allows accurate determination of the self-propelled swimming (SPS) speed of both rigid and flexible membrane-like foils made of shark skin and two biomimetic models of shark skin to measure locomotor performance. We studied the SPS speed of real shark skin, a silicone riblet material with evenly spaced ridges and a Speedo® 'shark skin-like' swimsuit fabric attached to rigid flat-plate foils and when made into flexible membrane-like foils. We found no consistent increase in swimming speed with Speedo® fabric, a 7.2% increase with riblet material, whereas shark skin membranes (but not rigid shark skin plates) showed a mean 12.3% increase in swimming speed compared with the same skin foils after removing the denticles. Deformation of the shark skin membrane is thus crucial to the drag-reducing effect of surface denticles. Digital particle image velocimetry (DPIV) of the flow field surrounding moving shark skin foils shows that skin denticles promote enhanced leading-edge suction, which might have contributed to the observed increase in swimming speed. Shark skin denticles might thus enhance thrust, as well as reduce drag.
长期以来，人们一直怀疑鲨鱼皮的齿状物可以减少运动时的水动力阻力，并且已经生产出许多据称可以利用鲨鱼皮般的表面粗糙度来减少游泳时阻力的人造材料。但是，迄今为止，没有研究在动态和受控条件下测试这些减少阻力的说法，这些条件可以定量比较鲨鱼皮和类似皮肤的材料的游泳速度和流体动力学与缺乏表面装饰或具有不同取向的表面的对照。我们使用一种拍打翼机器人设备，该设备可以准确确定由鲨鱼皮制成的刚性和柔性膜状翼片的自推进游泳（SPS）速度，以及两种鲨鱼皮仿生模型，以测量运动性能。我们研究了真实鲨鱼皮、具有均匀间隔脊的硅树脂肋纹材料以及附着在刚性平板翼片上的 Speedo®“鲨鱼皮样”泳衣织物的 SPS 速度，以及制成柔性膜状翼片时的 SPS 速度。我们发现 Speedo®织物没有一致的游泳速度增加，肋纹材料增加了 7.2％，而鲨鱼皮膜（而不是刚性鲨鱼皮板）与去除齿状物后的相同皮翼相比，游泳速度平均增加了 12.3％。因此，鲨鱼皮膜的变形对于表面齿状物的减阻效果至关重要。移动鲨鱼皮翼片周围流场的数字粒子图像测速（DPIV）显示，皮肤齿状物促进了前缘的增强抽吸，这可能是观察到的游泳速度增加的原因。鲨鱼皮齿状物因此可以增强推力并减少阻力。
