Submarine dolphins 3d model skin#
The broad success of describing the flush-skin pigmentation patterns of animals using the RD framework gives confidence that the raised skin patterns on sharks and dolphins may have evolved by simultaneous diffusion in the surface-normal and lateral directions to interact with the flow in a similar fashion. Experiments coupled to self-regulation modeling show 17, 19 that, if the pigmentation is selectively ablated, the altered pattern forms the initial condition for a new pattern that is predictably generated, validating the underlying dynamic self-regulating nature. In these biochemical RD systems, two substances diffuse at different rates to generate the stationary surface patterns. Many slow-swimming animals, such as seashells and zebrafish, have organized patterns of surface pigmentation, which, although flush with the surface, can be modeled as reaction-diffusion (RD) systems 15, 16, 17, 18, 19. Hypothesis of organized skin patterning in sharks and dolphins We discuss their relevance to very low Reynolds number wall turbulence. Here, we explore whether synchronization of oscillations in the lateral diffusion of vorticity is such a mechanism and whether there is a minimalist (systemic) mechanism of wall-turbulence regeneration that is amenable to analytical investigations of control. It is not known whether the seemingly disparate skin patterns of sharks and dolphins and even their passive and active approaches, are in fact related to any universal mechanism of organizing the near-wall vorticity patterns or whether this mechanism is more extensively applicable to biological systems ( Fig. Measurements on simulated riblets (sans dd) 11, 12, 13 and engineered compliant coatings 6, 8, 9, 14 have been reported. Experiments show that a transfer of energy of flow instabilities to the damping surface stabilizes the flow 9, 10. The soft skin of dolphins, on the other hand, has arrays of lateral grooves and has been shown to vibrate via the underlying musculature 3, 4, 6, 7, 8. These two wavelengths resemble those of the dd and riblets. In the baseline turbulent boundary layers (TBL) over smooth surfaces, instabilities yield oscillations of two lateral wavelengths: one is manifested in streamwise streaks and the other, which is a product of the interaction between the streaks and the mean flow, has a sub-streak wavelength 5. The armor-like skin of sharks has two types of organization-a larger-scale nesting of tessellated dermal denticles (dd) on which three to six parallel riblets reside 2. Here, we carry out a spatiotemporal analytical modeling of the hydrodynamic interaction of these proud static and dynamic patterns with the surrounding water flow at low Reynolds numbers to understand the mechanisms causing the delays in onset of disorganization in the near-wall organization of fluid vorticity that allow sharks and dolphins to swim faster than would be possible otherwise. They have organized patterns of skin that stand proud 2, 3, 4.
The model shows that the adaptation mechanisms of sharks and dolphins to their fluid environment have much in common.
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. 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. 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. In contrast, sharks and dolphins contend with wall turbulence, are fast swimmers and have more organized skin patterns that are proud and sometimes vibrate. 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.
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