Drag Reduction Study about Bird Feather Herringbone Riblets

Flying bird has gradually formed airworthy structures e.g. streamlined shape and hollow shaft of feather to improve flying performance by millions of years natural selection. As typical property of flight feather, herringbone-type riblets can be observed along the shaft of each feather, which caused by perfect alignment of barbs. Why bird feather have such herringbone-type riblets has not been extensively discussed until now. In this paper, microstructures of secondary feathers are investigated through SEM photo of various birds involving adult pigeons, wild goose and magpie. Their structural parameters of herringbone riblets of secondary flight feather are statistically obtained. Based on quantitative analysis of feathers structure, one novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 15%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.

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Investigation of the Turbulent Drag Reduction Mechanism of a Kind of Microstructure on Riblet Surface

Micromachines ◽

10.3390/mi12010059 ◽

2021 ◽

Vol 12 (1) ◽

pp. 59

Author(s):

Mingrui Ao ◽

Miaocao Wang ◽

Fulong Zhu

Keyword(s):

Drag Reduction ◽

Three Dimensional ◽

Reduction Rate ◽

Water Area ◽

Reduction Mechanism ◽

Surface Drag ◽

Groove Surface ◽

Turbulent Drag ◽

Micro Structures ◽

Riblet Surface

With the k-ε renormalization group turbulence model, the drag reduction mechanism of three- dimensional spherical crown microstructure of different protruding heights distributing on the groove surface was studied in this paper. These spherical crown microstructures were divided into two categories according to the positive and negative of protruding height. The positive spherical crown micro-structures can destroy a large number of vortexes on the groove surface, which increases relative friction between water flow and the groove surface. With decreasing the vertical height of the spherical crown microstructure, the number of rupture vortexes gradually decreases. Due to the still water area causes by the blocking effect of the spherical crown microstructure, it was found that the shear stress on the groove surface can be reduced, which can form the entire drag reduction state. In another case, the spherical crown microstructures protrude in the negative direction, vortexes can be generated inside the spherical crown, it was found that these vortexes can effectively reduce the resistance in terms of pressure and friction. In a small volume, it was shown that the surface drag reduction rate of spherical crown microstructures protrudes in negative directions can be the same as high as 24.8%.

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Experimental Study of the Concave Bionic Drag Reduction Needles

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.461.702 ◽

2013 ◽

Vol 461 ◽

pp. 702-706

Author(s):

Ji Yue Wang ◽

Qian Cong

Keyword(s):

Drag Reduction ◽

Reduction Rate ◽

Outer Wall ◽

Comparative Test ◽

Point Of View ◽

National Standard ◽

Reduction Mechanism ◽

Laser Material ◽

Maximum Drag Reduction ◽

Smooth Design

In this paper, we have started from the point of view of bionics, doing surface bionic non-smooth design at the standard No.16 animal syringe needles. Then treating the concave as the bionic unit, we worked out the concave bionic drag reduction needles by use of the laser material remove processing means. In accordance with the national standard on the injection drag test of disposable needles, we did the puncture drag comparative test of the smooth needles and the bionic needles, getting the correspondence relationship between the drag reduction rate and the bionic unit parameters. We found that the maximum drag reduction rate up to 44.05%, and it appeared when the concave interval was 0.9mm and the concave diameter was 0.09mm. Then through discussing the drag reduction mechanism of the bionic needles, we knew that the bionic units reduced the actual contact area between the needle outer wall and the simulation skin, and it was the main reason of bionic needles puncture drag decreases.

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Bionic Nonsmooth Drag Reduction Mathematical Model Construction and Subsoiling Verification

Applied Bionics and Biomechanics ◽

10.1155/2021/5113453 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Baoguang Wu ◽

Ruize Zhang ◽

Pengfei Hou ◽

Jin Tong ◽

Deyi Zhou ◽

...

Keyword(s):

Mathematical Model ◽

Drag Reduction ◽

Field Experiments ◽

Design Method ◽

Reduction Rate ◽

Movement Speed ◽

Surface Drag ◽

Movement Model ◽

Surface Design ◽

Pangolin Scale

In this study, a bionic nonsmooth drag-reducing surface design method was proposed; a mathematical model was developed to obtain the relationship between the altitude of the nonsmooth drag-reducing surface bulges and the spacing of two bulges, as well as the speed of movement, based on which two subsoiler shovel tips were designed and verified on field experiments. The mechanism of nonsmooth surface drag reduction in soil was analyzed, inspired by the efficient digging patterns of antlions. The nonsmooth surface morphology of the antlion was acquired by scanning electron microscopy, and a movement model of the nonsmooth surface in soil was developed, deriving that the altitude of the nonsmooth drag-reducing surface bulge is proportional to the square of the distance between two bulges and inversely proportional to the square of the movement speed. A flat subsoiler shovel tip and a curved tip were designed by applying this model, and the smooth subsoiler shovel tips and the pangolin scale bionic tips were used as controls, respectively. The effect of the model-designed subsoilers on drag reduction was verified by subsoiling experiments in the field. The results showed that the resistance of the model-designed curved subsoiler was the lowest, the resistance of the pangolin scale bionic subsoiler was moderate, and the resistance of the smooth surface subsoiler was the highest; the resistance of the curved subsoiler was less than the flat subsoilers; the resistance reduction rate of the model-designed curved subsoiler was 24.6% to 33.7% at different depths. The nonsmooth drag reduction model established in this study can be applied not only to the design of subsoilers but also to the design of nonsmooth drag reduction surfaces of other soil contacting parts.

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Study on the Drag Reduction Characteristics of the Surface Morphology of Paramisgurnus dabryanus Loach

Coatings ◽

10.3390/coatings11111357 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1357

Author(s):

Liyan Wu ◽

Jiaqi Wang ◽

Guihang Luo ◽

Siqi Wang ◽

Jianwei Qu ◽

...

Keyword(s):

Numerical Simulation ◽

Boundary Layer ◽

Drag Reduction ◽

Reduction Rate ◽

Underwater Vehicles ◽

Flow Channel ◽

Numerical Control ◽

Reduction Mechanism ◽

Paramisgurnus Dabryanus ◽

Reduction Characteristics

The drag reduction design of underwater vehicles is of great significance to saving energy and enhancing speed. In this paper, the drag reduction characteristics of Paramisgurnus dabryanus loach was explored using 3D ultra-depth field microscopy to observe the arrangement of the scales. Then, a geometric model was established and parameterized. A simulated sample was processed by computer numerical control (CNC) machining and tested through using a flow channel bench. The pressure drop data were collected by sensors, and the drag reduction rate was consequently calculated. The test results showed that the drag reduction rate of a single sample could reach 23% at a speed of 1.683 m/s. Finally, the experimental results were verified by numerical simulation and the drag reduction mechanism was explored. The boundary layer theory and RNG k-ε turbulence model were adopted to analyze the velocity contour, pressure contour and shear force contour diagrams. The numerical simulation results showed that a drag reduction effect could be achieved by simulating the microstructure of scales of the Paramisgurnus dabryanus loach, showing that the results are consistent with the flow channel experiment and can reveal the drag reduction mechanism. The bionic surface can increase the thickness of boundary layer, reduce the Reynolds number and wall resistance. The scales disposition of Paramisgurnus dabryanus loach can effectively reduce the surface friction, providing a reference for future research on drag reduction of underwater vehicles such as ships and submarines.

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Mechanism of Drag Reduction in Floating Plate of Paddy Field Based on CFD

Complexity ◽

10.1155/2020/8852941 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Xiaoze Yu ◽

Baofeng Zhang ◽

Jiahan You

Keyword(s):

Drag Reduction ◽

Paddy Field ◽

Optimization Design ◽

Structural Parameters ◽

Elevation Angle ◽

Bottom Surface ◽

Reduction Mechanism ◽

Floating Plate ◽

Vof Model ◽

Working Resistance

In order to study drag reduction mechanism in mud parts’ operation of surface machine tools for paddy field, this paper takes floating plate, the main working part of laminating mechanism, as the research object and systematically analyzes the mechanism of action of elevation angle, curved angle, penetrating angle, and local microstructure of floating plate on working resistance and local fluid flow characteristics of the laminating structure based on VOF model in Fluent. Using ship mechanics theory and fluid lubrication theory, the drag reduction mechanism under different structural parameters of the floating plate is analyzed. The results show that, compared with the ordinary floating plate, the pressure difference resistance can be reduced by increasing the elevation angle by 60°, curved angle by 20°, and mud separation angle by 20°. The increase of the concave nonsmooth bottom surface structure can reduce viscous frictional resistance, and the total working resistance after structural optimization is comparatively reduced by 48.3%, with lowered hilling height in the forward direction and improved lubrication condition of the bottom surface, forming liquid lubrication effect. This study can provide theoretical references for the optimization design of muddy soil mud parts, mud-machine interaction research, and the development of paddy field laminating mechanism.

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Global effect of local skin friction drag reduction in spatially developing turbulent boundary layer

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.545 ◽

2016 ◽

Vol 805 ◽

pp. 303-321 ◽

Cited By ~ 14

Author(s):

A. Stroh ◽

Y. Hasegawa ◽

P. Schlatter ◽

B. Frohnapfel

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Drag Reduction ◽

Control Region ◽

Reduction Rate ◽

Wall Turbulence ◽

Local Skin ◽

Control Schemes ◽

Local Skin Friction ◽

Friction Drag Reduction

A numerical investigation of two locally applied drag-reducing control schemes is carried out in the configuration of a spatially developing turbulent boundary layer (TBL). One control is designed to damp near-wall turbulence and the other induces constant mass flux in the wall-normal direction. Both control schemes yield similar local drag reduction rates within the control region. However, the flow development downstream of the control significantly differs: persistent drag reduction is found for the uniform blowing case, whereas drag increase is found for the turbulence damping case. In order to account for this difference, the formulation of a global drag reduction rate is suggested. It represents the reduction of the streamwise force exerted by the fluid on a plate of finite length. Furthermore, it is shown that the far-downstream development of the TBL after the control region can be described by a single quantity, namely a streamwise shift of the uncontrolled boundary layer, i.e. a changed virtual origin. Based on this result, a simple model is developed that allows the local drag reduction rate to be related to the global one without the need to conduct expensive simulations or measurements far downstream of the control region.

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Biomimetic Drag Reduction Study on Herringbone Riblets of Bird Feather

Journal of Bionic Engineering ◽

10.1016/s1672-6529(13)60229-2 ◽

2013 ◽

Vol 10 (3) ◽

pp. 341-349 ◽

Cited By ~ 34

Author(s):

Huawei Chen ◽

Fugang Rao ◽

Xiaopeng Shang ◽

Deyuan Zhang ◽

Ichiro Hagiwara

Keyword(s):

Drag Reduction ◽

Bird Feather

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An investigation on the drag reduction performance of bioinspired pipeline surfaces with transverse microgrooves

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.11.3 ◽

2020 ◽

Vol 11 ◽

pp. 24-40 ◽

Cited By ~ 1

Author(s):

Weili Liu ◽

Hongjian Ni ◽

Peng Wang ◽

Yi Zhou

Keyword(s):

Numerical Simulation ◽

Drag Reduction ◽

Pressure Loss ◽

Fluid Transport ◽

Reduction Rate ◽

Orthogonal Analysis ◽

Maximum Drag Reduction ◽

Reduction Effect ◽

Save Energy ◽

Microgrooved Surface

A novel surface morphology for pipelines using transverse microgrooves was proposed in order to reduce the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of these bionic pipelines. It was found that the vortex ‘cushioning’ and ‘driving’ effects produced by the vortexes in the microgrooves were the main reason for obtaining a drag reduction effect. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient. Altogether, bionic pipelines achieved drag reduction effects both in a pipeline and in a concentric annulus flow model. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by an orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% could be achieved. The numerical simulation and experimental results were cross-checked and found to be consistent with each other, allowing to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. These results can provide theoretical guidance to save energy in pipeline transportations.

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Influence of Phenylmethylsilicone Oil on Anti-Fouling and Drag-Reduction Performance of Silicone Composite Coatings

Coatings ◽

10.3390/coatings10121239 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1239

Author(s):

Qiang Yang ◽

Zhanping Zhang ◽

Yuhong Qi ◽

Hongyang Zhang

Keyword(s):

Drag Reduction ◽

Removal Rate ◽

Composite Coatings ◽

Reduction Rate ◽

Selection Experiment ◽

Adhesion Test ◽

Fouling Release ◽

Bacteria Adhesion ◽

Addition Amount ◽

Adhesion Factor

In this study, we explore the effect of phenylmethylsilicone oil (PSO) addition amount and viscosity in a fouling release coating based on polydimethylsiloxane (PDMS). The surface properties, mechanical properties, anti-fouling and drag-reduction performance of the coating were studied. Meanwhile the influence of the basic properties of the coating on the anti-fouling and drag-reduction performance was also studied. Subsequently, the antifouling performance of the coating was investigated by the Navicula Tenera and bacteria adhesion test. As a result, the high content of PSO paint has a high foul removal rate. The incorporation of PSO into paint can reduce the elastic modulus and surface energy of the coating to reduce its relative adhesion factor (RAF). The lower the RAF, the better the antifouling effect of the coating. The drag-reduction performance of the coating was verified by the torque selection experiment, and the results showed that incorporation of PSO into paint can enhance the elongation and hydrophobicity of the coating, thereby increasing the drag reduction rate of the coating.

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