Bandyopadhyay Promode R, Hellum Aren M
Naval Undersea Warfare Center, Newport, RI 02841, USA.
Sci Rep. 2014 Oct 23;4:6650. doi: 10.1038/srep06650.
Many slow-moving biological systems like seashells and zebrafish that do not contend with wall turbulence have somewhat organized pigmentation patterns flush with their outer surfaces that are formed by underlying autonomous reaction-diffusion (RD) mechanisms. In contrast, sharks and dolphins contend with wall turbulence, are fast swimmers, and have more organized skin patterns that are proud and sometimes vibrate. A nonlinear spatiotemporal analytical model is not available that explains the mechanism underlying control of flow with such proud patterns, despite the fact that shark and dolphin skins are major targets of reverse engineering mechanisms of drag and noise reduction. Comparable to RD, a minimal self-regulation model is given for wall turbulence regeneration in the transitional regime--laterally coupled, diffusively--which, although restricted to pre-breakdown durations and to a plane close and parallel to the wall, correctly reproduces many experimentally observed spatiotemporal organizations of vorticity in both laminar-to-turbulence transitioning and very low Reynolds number but turbulent regions. We further show that the onset of vorticity disorganization is delayed if the skin organization is treated as a spatiotemporal template of olivo-cerebellar phase reset mechanism. The model shows that the adaptation mechanisms of sharks and dolphins to their fluid environment have much in common.
许多像贝壳和斑马鱼这样行动缓慢、无需应对壁面湍流的生物系统，其外表面有一些由潜在的自主反应扩散（RD）机制形成的色素沉着模式，这些模式较为规整。相比之下，鲨鱼和海豚需要应对壁面湍流，是快速游动的生物，它们有着更为规整的皮肤图案，这些图案向外突出，有时还会振动。尽管鲨鱼和海豚的皮肤是减阻和降噪逆向工程机制的主要研究对象，但目前尚无一个非线性时空分析模型能够解释这种突出图案控制流动的潜在机制。与反应扩散类似，我们给出了一个过渡区域壁面湍流再生的最小自调节模型——横向耦合、扩散式的——该模型虽然仅限于预崩溃阶段以及靠近壁面且与壁面平行的平面，但能正确再现层流到湍流过渡阶段以及极低雷诺数但湍流区域中许多实验观察到的涡度时空组织。我们进一步表明，如果将皮肤组织视为橄榄小脑相位重置机制的时空模板，涡度紊乱的起始会延迟。该模型表明，鲨鱼和海豚对其流体环境的适应机制有许多共同之处。
