Windbreak fences in open and urban areas can be used to effectively reduce the wind velocity. In this paper we examine how the geometrical shape of the windbreak fence can optimally mitigate wind velocity. We propose ...Windbreak fences in open and urban areas can be used to effectively reduce the wind velocity. In this paper we examine how the geometrical shape of the windbreak fence can optimally mitigate wind velocity. We propose an approach for windbreak fence design based on a bionic parametric model of the shark skin denticle geometry, which improves the reduction of the wind velocity around and behind the windbreak fences. The generative model was used to estimate improvements by variations in the parameters of the fence panel＇s geometrical shape, inspired by shark skin denticles. The results of the Computational Fluid Dynamics （CFD） analysis indicates that the fence surface inspired by shark skin performs much better than both flat and cor- rugated surfaces. Taking into account the complex geometry of the surface inspired by shark skin denticles, we propose a fab- rication process using an expanded polystyrene foam （EPS） material, created using an industrial robot arm with a hot-wire tool. Creating EPS moulds for the shark skin denticle panels allows for a richer variety material to be used in the final design, leading both to higher efficiency and a more attractive design.展开更多
The shortfin mako shark(Isurus oxyrinchus)is one of the fastest marine fishes,reaching speeds of up to 70 km·h^-1.Their speed is related to the skin surface design composed of dermal denticles.Denticles vary in s...The shortfin mako shark(Isurus oxyrinchus)is one of the fastest marine fishes,reaching speeds of up to 70 km·h^-1.Their speed is related to the skin surface design composed of dermal denticles.Denticles vary in size and shape according to placement on the body and minimize turbulence around the body.The objective of this study is to analyze the interaction between seawater flow and denticles on the dorsal fin.High-resolution microscopy(scanning electron microscopy and confocal microscopy)were used to measure defined parts of the dermal denticles.These measurements,along with ratios based on length-to-width define three morphologies(rounded,semi-rounded,long)that were 3D reconstructed.Computational fluid dynamics simulated fluid passage over reconstructed denticles and describe hy-drodynamic efficiency under different conditions.An increase in angle of inclination produced a relevant increase in the drag coefficient,especially for high velocity inlets.The lowest drag coefficient values were found in long and semi-rounded,followed by rounded mor-phologies.The hydrodynamic behavior of shark skin demonstrates a relation to the morphological characteristics of dermal denticles on the dorsal fin.It is concluded that the best hydroefficiency relies on the rounded morphology and may serve to design hydrodynamically efficient surfaces or manmade assemblies.展开更多
While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be capable of achieving turbulent flow control and drag reduction, sharkskin-inspired ＂riblets...While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be capable of achieving turbulent flow control and drag reduction, sharkskin-inspired ＂riblets＂ have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and mod- eling of＂fresh＂ denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold： （1） 2D imaging of lubricated sharkskin in a wet state by means of a ＂nano-suit＂ technique with a Field-Emission Scanning Electron Microscope （FE-SEM）; （2） 3D structures of sharkskin denticles with a micro-focus X-ray CT; and （3） single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges （herein termed ＂non-uniform grooves＂） with Angles Of Inclination （AOI） ranging over 20° - 32°. Hydrodynamics associated with the unique five-ridge denticles were then in- vestigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.展开更多
文摘Windbreak fences in open and urban areas can be used to effectively reduce the wind velocity. In this paper we examine how the geometrical shape of the windbreak fence can optimally mitigate wind velocity. We propose an approach for windbreak fence design based on a bionic parametric model of the shark skin denticle geometry, which improves the reduction of the wind velocity around and behind the windbreak fences. The generative model was used to estimate improvements by variations in the parameters of the fence panel＇s geometrical shape, inspired by shark skin denticles. The results of the Computational Fluid Dynamics （CFD） analysis indicates that the fence surface inspired by shark skin performs much better than both flat and cor- rugated surfaces. Taking into account the complex geometry of the surface inspired by shark skin denticles, we propose a fab- rication process using an expanded polystyrene foam （EPS） material, created using an industrial robot arm with a hot-wire tool. Creating EPS moulds for the shark skin denticle panels allows for a richer variety material to be used in the final design, leading both to higher efficiency and a more attractive design.
文摘The shortfin mako shark(Isurus oxyrinchus)is one of the fastest marine fishes,reaching speeds of up to 70 km·h^-1.Their speed is related to the skin surface design composed of dermal denticles.Denticles vary in size and shape according to placement on the body and minimize turbulence around the body.The objective of this study is to analyze the interaction between seawater flow and denticles on the dorsal fin.High-resolution microscopy(scanning electron microscopy and confocal microscopy)were used to measure defined parts of the dermal denticles.These measurements,along with ratios based on length-to-width define three morphologies(rounded,semi-rounded,long)that were 3D reconstructed.Computational fluid dynamics simulated fluid passage over reconstructed denticles and describe hy-drodynamic efficiency under different conditions.An increase in angle of inclination produced a relevant increase in the drag coefficient,especially for high velocity inlets.The lowest drag coefficient values were found in long and semi-rounded,followed by rounded mor-phologies.The hydrodynamic behavior of shark skin demonstrates a relation to the morphological characteristics of dermal denticles on the dorsal fin.It is concluded that the best hydroefficiency relies on the rounded morphology and may serve to design hydrodynamically efficient surfaces or manmade assemblies.
文摘While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be capable of achieving turbulent flow control and drag reduction, sharkskin-inspired ＂riblets＂ have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and mod- eling of＂fresh＂ denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold： （1） 2D imaging of lubricated sharkskin in a wet state by means of a ＂nano-suit＂ technique with a Field-Emission Scanning Electron Microscope （FE-SEM）; （2） 3D structures of sharkskin denticles with a micro-focus X-ray CT; and （3） single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges （herein termed ＂non-uniform grooves＂） with Angles Of Inclination （AOI） ranging over 20° - 32°. Hydrodynamics associated with the unique five-ridge denticles were then in- vestigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.
