INFLUENCE OF MORPHOLOGY FOR DRAG REDUCTION EFFECT OF SHARKSKIN SURFACE

2014 ◽  
Vol 14 (02) ◽  
pp. 1450029 ◽  
Author(s):  
YUEHAO LUO ◽  
YUFEI LIU ◽  
DEYUAN ZHANG ◽  
E. Y. K. NG
Keyword(s):  
Natural Selection ◽  
Flow Field ◽  
Drag Reduction ◽  
Hydrophobic Effect ◽  
Academic Research ◽  
Engineering Application ◽  
Reduction Mechanism ◽  
Urgent Problem ◽  
Micro Flow ◽  
Reduction Effect

Through millions of years' natural selection, creature has formed their own unique functional surfaces. Shark is one of the fastest animals in the ocean, which is well known for "sharkskin effect". Sharkskin surface is all covered by tiny and rigid scales with sophisticated morphology, which is one important factor to produce the high drag reducing efficiency. However, the drag reduction mechanism of sharkskin has not been understood thoroughly, which has developed into an urgent problem to be resolved. In this paper, the accurate 3D digital model of sharkskin surface is constructed based on the biological prototype and the micro flow field on the near wall is analyzed comprehensively and deeply. In addition, the drag reduction mechanism is explored from different aspects, especially which, the influences of the variation of attack angles of scales, the super-hydrophobic effect and nanochain of mucus on drag-reducing efficiency are taken into consideration, which has great significance on academic research and engineering application.

Numerical Simulation of Micro Flow Field on Biomimetic Sharkskin Micro-Grooved Surface

2014 ◽  
Vol 884-885 ◽  
pp. 378-381 ◽  
Author(s):  
Yue Hao Luo ◽  
Yu Fei Liu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Drag Reduction ◽  
Reduction Mechanism ◽  
Urgent Problem ◽  
Grooved Surface ◽  
Micro Flow ◽  
Important Significance

It is well-known that sharkskin surface has the effect of inhibiting the occurrence of turbulence and reducing the wall resistance, however, the drag reduction mechanism has developed into an urgent problem to be resolved now. According to the actual circumstance, for purpose of obtaining the best drag-reducing efficiency, the biomimetic sharkskin micro-grooved surface is designed according to the relevant literatures and research achievements, and numerical simulation of the micro flow field on the biomimetic sharkskin surface is carried out comprehensivley, which has the important significance to explain the drag reduction mechanism.

A tracer dispersion study of the drag-reduction effect in a turbulent pipe flow

1971 ◽  
Vol 47 (2) ◽  
pp. 209-230 ◽  
Author(s):  
A. W. Bryson ◽  
Vr. Arunachalam ◽  
G. D. Fulford
Keyword(s):  
Molecular Weight ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Viscous Sublayer ◽  
Turbulent Pipe Flow ◽  
Reduction Mechanism ◽  
Response Curves ◽  
Pipe Flows ◽  
Tracer Dispersion ◽  
Reduction Effect

Remarkable differences in dispersion of a tracer material injected into turbulent pipe flows of water and water containing as little as 2·5 parts per million by weight of a soluble high-molecular-weight drag-reducing polyoxyethylene additive have been measured. Analysis of the tracer response curves in terms of a simple one-parameter model shows that the observed results are compatible with a drag-reduction mechanism based on thickening of the viscous sublayer adjoining the wall. Other experiments, reported briefly, suggest that polymer adsorption on to the wall is responsible for this thickening.

The Numerical Research of Drag Reduction over Bionic Fluctuation-Adaptive Non-Smooth Surface

2014 ◽  
Vol 939 ◽  
pp. 499-505
Author(s):  
Ya Lun Hu ◽  
Meng Lei Zhu ◽  
Jun Xiao ◽  
Xing Zhen Wang ◽  
Zhong Xu
Keyword(s):  
Flow Field ◽  
Drag Reduction ◽  
Traveling Wave ◽  
Smooth Surface ◽  
Frictional Resistance ◽  
Stream Velocity ◽  
Flow State ◽  
Series Of Experiments ◽  
Reduction Effect ◽  
The Relationship

This paper does some research about the drag reduction mechanism of dolphins soft and adaptive skin in view of bionics. The study shows that dolphin skin is very sensitive to pressure changed by external flow field, and can do a wave-like movement with the uneven pressure, resulting in a traveling wave of the non-smooth surface which reducing frictional resistance on the wall surface in the turbulent flow field. Based on Karman vortex street and momentum theory, we described the relationship between the geometry of traveling wave and the drag reduction efficiency, and with the help of numerical simulations of traveling wave surface using RNG k-ε model and a series of experiments, we get the friction coefficient near the wall boundary, the turbulence intensity, and the distribution of the velocity field. The results show that, compared with smooth surface, the non-smooth surface of traveling wave reduces frictional resistance of the adhesion surface owing to changing the fluid flow state. Moreover, the non-smooth surface of traveling wave shows significant drag reduction effect at the stream velocity about 6 m / s.

scholarly journals Research on Control Technology of Jet and Rectifying Cone Combined Flow Field

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Hongqing Lv ◽  
Lei Xu ◽  
Zhenqing Wang ◽  
Xiaobin Zhang
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Drag Reduction ◽  
High Speed ◽  
Bluff Body ◽  
Hot Spot ◽  
Pressure Ratio ◽  
Main Flow ◽  
Control Technology ◽  
Reduction Effect

As an active flow field control technology, reverse jet and rectifier cone can significantly affect the flow field around the high-speed aircraft and reduce the drag and heat of high-speed aircraft to a certain extent. In this paper, the CFD numerical method is used to simulate and analyze the flow around the bluff body front rectifier cone and the reverse jet interference flow field. Further considering the combination of the two, the flow field structure around the bluff body under the combination of rectifying cone and reverse jet flow was simulated. Research shows, for the flow field of a single reverse jet, the pressure ratio of the reverse jet to the main flow has a significant effect on the drag reduction performance. With the change of the pressure ratio of the jet to the main flow, two modes of long jet and short jet will appear. The structure of the short jet modal flow field is relatively stable. However, with the increase of attack angle, the shear layer of free flow will attach to the shock wave and form hot spot, which is a great threat to high-speed aircraft. When the rectifier cone and the reverse jet are combined, within a certain angle of attack, the wall will not form a reattachment shock wave. The area behind the bow shock and in front of the aircraft head is a free-state zone, which has a good cooling effect on the aircraft head. At the same time, the static pressure on the wall is reduced, which has a very good drag reduction effect.

Experimental study on the drag reduction effect of a rotating superhydrophobic surface in micro gap flow field

2016 ◽  
Vol 23 (8) ◽  
pp. 3033-3040 ◽  
Author(s):  
Chunze Wang ◽  
Fei Tang ◽  
Pengfei Hao ◽  
Qi Li ◽  
Xiaohao Wang
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Gap Flow ◽  
Reduction Effect

RECENT PROGRESS IN EXPLORING DRAG REDUCTION MECHANISM OF REAL SHARKSKIN SURFACE: A REVIEW

2015 ◽  
Vol 15 (03) ◽  
pp. 1530002 ◽  
Author(s):  
YUEHAO LUO
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Recent Progress ◽  
Daily Life ◽  
Reduction Mechanism ◽  
Reduction Effect ◽  
Morphology Influence ◽  
Long Chains

It has gradually developed into an undisputable fact that sharkskin surface has the obvious drag reduction effect compared with the absolutely smooth skins, and it has been put into application widely, which has brought great advantages and profits in daily life, industry and agriculture. Because some problems in turbulence are not resolved completely and perfectly, the drag reduction mechanism of real sharkskin has also not been understood absolutely and thoroughly so far. However, many researchers have carried out lots of the relevant experiments and analyses, very plentiful and important conclusions are obtained, which can explain some certain phenomena of sharkskin drag reduction effect. An overview of exploring drag reduction mechanism of real sharkskin surface is systemically presented in detail. These mechanisms include inhibition of turbulence using micro/nano structured morphology, influence of scale's attack angles, nano-long chains and boundary layer slipping based on superhydrophobicity. This paper will improve the comprehension of the drag reduction mechanism and expand biomimetic sharkskin technology into more applications.

Study on drag reduction mechanism of rotating disk with micro-grooves

2017 ◽  
Vol 232 (6) ◽  
pp. 660-673
Author(s):  
Suping Wen ◽  
Wenbo Wang ◽  
Jian Wang
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Viscous Sublayer ◽  
Dual Function ◽  
Reduction Mechanism ◽  
Smooth Disk ◽  
Reduction Effect ◽  
Interaction Phenomenon

This paper presents the drag reduction mechanism of a rotating disk with micro-grooves. The flow characteristics of the micro-grooved disk at various rotating Reynolds numbers are investigated using experiments and large-eddy simulations. The results show that fluid in the gap between the disks undergoes circumferential movement, but fluid within the micro-grooves undergoes radial movement because of the dual function of wall rejection and boundary layer blockage. As a result, fluid within the micro-grooves moves very slowly and quietly. Hence, quiet and slow-moving fluid within the micro-grooves increases the thickness of the viscous sublayer and recedes mixed layer and suppresses the unstable motion. The mean relative velocity gradient of the immersed surface on the grooved disk becomes much lower than that of a smooth disk, and the contact area between the walls and the high-speed fluid is diminished. An interaction phenomenon between the micro-grooves and the gap could be discovered due to the micro-groove unenclosed structure. The interaction phenomenon makes the quiet fluid within the micro-grooves also suppresses the outside flow. Accordingly, a micro-grooved rotating disk has an obvious drag reduction effect compared with a rotating smooth disk.

CHEMICAL, MECHANICAL AND HYDRODYNAMIC PROPERTIES RESEARCH ON COMPOSITE DRAG REDUCTION SURFACE BASED ON BIOLOGICAL SHARKSKIN MORPHOLOGY AND MUCUS NANOLONG CHAIN

2015 ◽  
Vol 15 (05) ◽  
pp. 1550084 ◽  
Author(s):  
YUEHAO LUO ◽  
DEYUAN ZHANG ◽  
YUFEI LIU ◽  
YUANYUE LI ◽  
E. Y. K. NG
Keyword(s):  
Natural Selection ◽  
Drag Reduction ◽  
Water Tunnel ◽  
Reduction Mechanism ◽  
Hydrodynamic Properties ◽  
The World ◽  
Smooth Skin ◽  
Survival Of The Fittest ◽  
Important Significance ◽  
Long Chain

Natural selection, survival of the fittest. Through millions of years' evolution, shark has become one of the fastest swimming animals in the ocean, and it is very well-known for sharkskin effect, especially for "sharkskin swimsuit". Due to its great superior properties in drag reduction, anti-wear, self-cleaning and so on, the investigations on the essential mechanisms and fabricating methods have attracted so much attention from all over the world, and the achievements have been widely put into application in industry, agriculture, transportation, airspace and so on, and so lots of profits have been obtained so far. In this paper, the method of fabricating artificial composite drag reduction surface based on biological sharkskin morphology and mucus nano-long chain is investigated and studied, the chemical, mechanical and hydrodynamic properties are explored from different aspects in depth, in which, the experimental results in water tunnel showed that the drag-reducing efficiency could surpass 20% with the smooth skin as reference, and the drag reduction mechanism is systematically explained and discussed from different aspects, which has important significance to understand the recent research status and expand the applications of sharkskin in the fluid engineering.

HYDRODYNAMIC TESTING OF A BIOLOGICAL SHARKSKIN REPLICA MANUFACTURED USING THE VACUUM CASTING METHOD

2015 ◽  
Vol 22 (02) ◽  
pp. 1550030 ◽  
Author(s):  
YUEHAO LUO ◽  
YUFEI LIU ◽  
DE YUAN ZHANG
Keyword(s):  
Drag Reduction ◽  
Aerospace Industry ◽  
Air Bubbles ◽  
Urgent Problem ◽  
Casting Method ◽  
Vacuum Casting ◽  
Practical Applications ◽  
Smooth Skin ◽  
Reduction Effect ◽  
Hydrodynamic Testing

Numerous facts have validated that sharkskin possesses the obvious drag reduction effect in certain turbulent flowing stations, and it has huge potential and important applications in the fields of agriculture, aerospace, industry, transportation, daily life and so on, which have attracted increased attention throughout the world. To meet the increasing requirements of practical applications, it has been progressively developing into an urgent problem to manufacture sharkskin surfaces with perfect forming quality and high drag-reducing effect. In this paper, the vacuum casting method is put forward to fabricate the drag-reducing surface with the real sharkskin morphology by eliminating the air bubbles from the bottom of sophisticated morphology in the pouring process. Meanwhile, a novel and facile “marking key point” method is explored and adopted to search for the corresponding biological sharkskin and negative template, a more convincing way to evaluate the replicating precision is systematically illustrated and the hydrodynamic experiment is carried out in the water tunnel. The results indicate that wall resistance over sharkskin surface replicated by the vacuum casting method can be decreased by about 12.5% compared with the smooth skin. In addition, the drag reduction mechanism hypotheses of sharkskin are generalized from different respects. This paper will improve the comprehension of the sharkskin fabrication method and expand biomimetic sharkskin technology into more applications in the fluid engineering.

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