School of Mathematics, Computer Science and Engineering, City, University of London, London, EC1V 0HB, UK.
Institut für Aerodynamik und Gasdynamik, Universität Stuttgart, Pfaffenwaldring 21, 70569, Stuttgart, Germany.
Sci Rep. 2020 Sep 3;10(1):14534. doi: 10.1038/s41598-020-71434-8.
Aquatic animals have developed effective strategies to reduce their body drag over a long period of time. In this work, the influence of the scales of fish on the laminar-to-turbulent transition in the boundary layer is investigated. Arrays of biomimetic fish scales in typical overlapping arrangements are placed on a flat plate in a low-turbulence laminar water channel. Transition to turbulence is triggered by controlled excitation of a Tollmien-Schlichting (TS) wave. It was found that the TS wave can be attenuated with scales on the plate which generate streamwise streaks. As a consequence, the transition location was substantially delayed in the downstream direction by 55% with respect to the uncontrolled reference case. This corresponds to a theoretical drag reduction of about 27%. We thus hypothesize that fish scales can stabilize the laminar boundary layer and prevent it from early transition, reducing friction drag. This technique can possibly be used for bio-inspired surfaces as a laminar flow control means.
水生动物经过长期的进化，已经形成了有效的减阻策略。在这项工作中，我们研究了鱼类鳞片对边界层中层流向湍流转捩的影响。采用典型重叠排列的仿生鱼鳞片阵列放置在低湍流层流水槽中的平板上。通过对 Tollmien-Schlichting（TS）波的受控激励来触发转捩到湍流。结果表明，在平板上布置生成流向条纹的鳞片可以减弱 TS 波。因此，与无控参考情况相比，下游方向的转捩位置延迟了 55%，这相当于理论上减少了约 27%的阻力。因此，我们假设鱼类鳞片可以稳定层流边界层并防止其过早转捩，从而减少摩擦阻力。该技术可能可用作仿生表面的层流控制手段。
