Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

Adhesive forces exist between soil and the surfaces of soil-engaging components; they increase working resistance and energy consumption. This paper tries to find an approach to reduce the adhesion and resistance of bulldozing plate. A simplified mechanical model of adhesion and resistance between soil and a non-smooth bulldozing plate is proposed. The interaction force between moist soil and a non-smooth bulldozing plate is analyzed. The pressure and friction distribution on the bulldozing plate are computed, and the anti-adhesive effect of a corrugated bulldozing plate is simulated numerically. Numerical results show that the wavy bulldozing plate achieves an effective drag reduction in moist soil. The optimal wavy shape of the corrugated bulldozing plate with the minimal resistance is designed. The basic principle of reducing soil adhesion of the non-smooth surface is discovered.     

A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

1IntroductionAdhesive forces exist between soil and the surfacesof soil-engaging components[1,2].Soil adhesion increasesthe running resistance and energy consumption,andaffects the operating quality.Soil adhesion also reducesthe working productivity of terrain machines,even worseit makes terrain machines fail to run.Reducing theadhesive force of the soil-engaging machines will have aprofound influence for cultivation.Through theinvestigation of soil animals,we have found that soilanimals poss…     

Bionic Research on Fish Scales for Drag Reduction

To reduce friction drag with bionic method in a more feasible way,the surface microstructure of fish scales was analyzed attempting to reveal the biologic features responding to skin friction drag reduction.Then comparable bionic surface mimicking fish scales was fabricated through coating technology for drag reduction.The paint mixture was coated on a substrate through a self-developed spray-painting apparatus.The bionic surface with micron-scale caves formed spontaneously due to the interfacial convection and deformation driven by interfacial tension gradient in the presence of solvent evaporation.Comparative experiments between bionic surface and smooth surface were performed in a water tunnel to evaluate the effect of bionic surface on drag reduction,and visible drag reduction efficiency was obtained.Numerical simulation results show that gas phase develops in solid-liquid interface of bionic surface with the effect of surface topography and partially replaces the solid-liquid shear force with gas-liquid shear force,hence reducing the skin friction drag effectively.Therefore,with remarkable drag reduction performance and simple fabrication technology,the proposed drag reduction technique shows the promise for practical applications.     

Design Principles of the Non-smooth Surface of Bionic Plow Moldboard

1　IntroductionTransferringbiologyfunctiontoengineeringtech nology[1] isaprominentprogressintechnologicalfields ,whichenrichesthecontentofTRIZsystematicmethod .Thenon smoothsurfacesofthetypicalsoilan imalshavetheeffectsofreducingsoiladhesion ,whichhasbeenconvincedandgraduallyaccepted .Thebionicplowmoldboardisanappliedexampleofimitatingthecharacteristicsofsoilanimals’surfaceappearancesandpracticingtheBionicTheoryofNon SmoothSurface(TNSS) .ThebasisofTNSSisnon smoothsurfaceef fects[2 ,3] …     

A Numerical Study on Pressure Drop in Microchannel Flow with Different Bionic Micro-Grooved Surfaces

The studies of bionics reveal that some aquatic animals and winged insects have developed an unsmoothed surface possessing good characteristics of drag reduction.In this paper,four types of bionic surfaces,placoid-shaped,V-shaped,riblet-shaped,and ridge-shaped grooved surfaces,are employed as the microchannel surfaces for the purpose of reducing pressure loss.Lattice Boltzmann Method (LBM),a new numerical approach on mescoscopic level,is used to conduct the numerical investigations.The results show that the micro-grooved surfaces possess the drag reduction performance.The existence of the vortices formed within the grooves not only decrease the shear force between fluid and wall but also minimize the contact area between fluid and walls,which can lead to a reduction of pressure loss.The drag reduction coefficient (η) for these four types of　micro-structures could be generalized as follows:ηridge-shaped ＞ ηV-shaped ＞ ηplacoid-shaped ＞ ηriblet-shaped.Besides,the geometrical optimizations for the ridge-shaped grooves,which have the highest drag reduction performance,are performed as well.The results suggest that,for the purpose of drag reduction,the ridge-shaped grooves with smaller width to height ratio are recommended for the lower Reynolds number flow,while the ridge-shaped grooves with larger width to height ratio are be more suitable for the larger Reynolds number flow.     

Experiment about Drag Reduction of Bionic Non-smooth Surface in Low Speed Wind Tunnel

The body surface of some organisms has non-smooth structure, which is related to drag reduction in moving fluid. To imitate these structures, models with a non-smooth surface were made. In order to find a relationship between drag reduction and the non-smooth surface, an orthogonal design test was employed in a low speed wind tunnel. Six factors likely to influence drag reduction were considered, and each factor tested at three levels. The six factors were the configuration, diameter/bottom width, height/depth, distribution, the arrangement of the rough structures on the experimental model and the wind speed. It was shown that the non-smooth surface causes drag reduction and the distribution of non-smooth structures on the model, and wind speed, are the predominant factors affecting drag reduction. Using analysis of variance, the optimal combination and levels were obtained, which were a wind speed of 44 m/s, distribution of the non-smooth structure on the tail of the experimental model, the configuratio     

Numerical Simulation of the Effect of Bionic Serrated Structures on the Aerodynamic Noise of a Circular Cylinder

Flow control can effectively reduce the aerodynamic noise radiated from a circular cylinder.As one of the flow control methods,a bionic method,inspired by the serrations at the leading edge of owls' wing,was proposed in this paper.The effects of bionic serrated structures arranged on the upper and lower sides of a cylinder on the aerodynamic and aeroacoustic performance of the cylinder were numerically investigated.At a free stream speed of 24.5 m·s-1,corresponding to Reynolds number of 1.58 × 104,the simulation results indicate that the bionic serrated structures can decrease the frequency of the vortex shedding and control the fluctuating aerodynamic force acting on the cylinder,thus reduce the aerodynamic noise.A qualitative-view of the vorticity in the wake of the cylinder suggest that the serrated structures reduce aerodynamic sound by suppressing the unsteady motion of vortices.     

Mechanical Properties and Microstructure of Bionic Non-Smooth Stainless Steel Surface by Laser Multiple Processing

Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processingtechnology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, samples of bionic non-smoothsurfaces of stainless steel 0Crl 8Ni9 were manufactured in the form of reseau structure by laser multiple processing. The mechanicalproperties (including microhardness, residual stress, surface roughness) and microstructure of the samples treated bylaser multiple processing were compared with those of the samples without LSP The results show that the mechanical propertiesof these samples by laser multiple processing were clearly improved in comparison with those of the samples without LSP Themechanisms underlying the improved surface microhardness and surface residual stress were analyzed, and the relations betweenhardness, comnressive residual stress and roughness were also presented.     

DEM Simulation of Clod Crushing by Bionic Bulldozing Plate

Through evolving over millions of years, earthworm has developed the typical wavy body surface. The non-smooth surface shape can break the clods into small pieces, which is one of the important reasons to make earthworm move freely in soil. Based on engineering bionics, the non-smooth body surface of earthworm was regarded as the bionic prototype, and a bionic wavy plane bulldozing plate was designed. In order to analyze the clod crushing mechanism by the bionic bulldozing plate, the nonlinear mechanical model of contact between soil particles was established and the clod-crushing processes by the bionic bulldozing plate and the smooth bulldozing plate were simulated by Distinct Element Method (DEM). Simulation results indicate that the bionic bulldozing plate has stronger clod-crushing ability and can break much more clods than the smooth bulldozing plate can.     

枯叶蛱蝶扑翼飞行的力学分析

模仿昆虫扑翼飞行的飞行器具有重量轻、质量小、噪音低、效率高、隐蔽性好等优点,在军用、民用领域被广泛地关注与应用.枯叶蛱蝶是典型的扑翼昆虫,在连续上升飞行过程中会出现停顿和跃升的现象.为了研究停顿和跃升现象的产生原因,对枯叶蛱蝶的翅型和扑翼行为进行了力学分析.通过测量鳞翅结构参数,记录飞行行为,运用能量守恒与动量守恒原理,考虑生物能的作用,视空气为不可压缩颗粒,建立了数学模型模拟枯叶蛱蝶飞行情况.结果表明,扑翼行为通过改变飞行动力的动量和分力大小来影响枯叶蛱蝶的飞行轨迹,鳞翅形状则通过改变飞行动力的大小来影响枯叶蛱蝶的飞行轨迹,扑翼行为导致停顿和跃升现象的产生.本文为设计扑翼型飞行器提供了力学仿生学基础与生物学模型,为进一步设计出更优化的仿生飞行器提供科学依据.     

Design and Analysis of Ternary Coupling Bionic Bits

In order to improve the penetration rate and the life of impregnated diamond bits, bionic coupling concept was introduced to the design of impregnated diamond bits. Ternary coupling bionic bits (briefly named bionic bits) were renascent non-smooth framework (three dimensional) manufactured by coupling physical and chemical methods from non-smooth shape and material. Experimental results show that bionic bits have higher penetration rate and longer life only when matrix material, matrix hardness and non-smooth ratio of the bits adapt to the strata to be drilled. Compared with the conventional impregnated diamond bits, the drilling rate and the life of bionic bits were increased by 43% and 74%, respectively.     

Bionic Design and Finite Element Analysis of Elbow in Ice Transportation Cooling System

With the increase in mining depth, mine heat harm has appeared to be more prominent. The mine heat harm could be resolvedor reduced by ice refrigeration. Thus, ice transportation through pipeline becomes a critical problem; typically flowresistance occurs in the elbow. In the present study, according to the analysis of the surface morphology of fish scale, abiomimetic functional surface structure for the interior wall of elbow is designed. Based on the theory of liquid-solid two phaseflow, a CFD numerical simulation of ice-water mixture flowing through the elbow is carried out using finite element method.Conventional experiments of pressure drop and flow resistance for both bionic and common elbows are conducted to test theeffect of the bionic elbow on flow resistance reduction. It is found that with the increase in the ice mass fraction in the ice-watermixture, the effect of bionic elbow on resistance reduction becomes more obvious.     

In vitro measurement and calculation of drag force on iliac limb stentgraft in a compliant arterial wall model

Interventional treatment of aortic aneurysms using endovascular stentgrafting is a minimally invasive technique. Following device implantation, transient drag forces act on the stentgraft. When the drag force exceeds the fixation force, complications like stentgraft migration, endoleaks and stentgraft failure occur. In such a scenario the device becomes unstable, causing concern over the long-term durability of endovascular repairs. The objective of this study is: (1) to measure the drag force on iliac limb stentgraft, having a distal diameter that is half the size of the proximal end, in an in vitro experiment; (2) to calculate the drag force using blood flow-compliant arterial wall interaction model and compare it with the measured values on the stentgraft for the in vitro experiment; (3) to calculate drag force on the stentgraft using physiological flow conditions. Experimental data for a stentgraft within a silicon tubing, representing a compliant artery, shows a peak drag force of 2.79 N whereas the calculation predicts a peak drag force of 2.57 N; thus a percentage difference of 7.8% is observed. When physiological flow and pressure pulse are used for the blood flow-compliant arterial wall computations, a peak drag force of 0.59 N is obtained for the same stentgraft that was used in the experiment. The outer cavity between the distal end of the iliac limb stentgraft and the arterial wall reduces the drag force. These forces can be used as design guideline for determining the fixation force needed for the stentgraft under physiological pulsatile flow.     

Biomechanics of swimming in the pufferfish Diodon holocanthus: propulsive momentum enhancement is an adaptation for thrust production in an undulatory median and paired-fin swimmer

A form of large-amplitude elongated-body theory appropriate for the analysis of undulatory fins attached to a rigid body of elliptical section suggests a benefit due to momentum enhancement relative to the fins on their own. This theoretical prediction is experimentally confirmed for the first time. Theoretical momentum enhancement factors for Diodon holocanthus (2.2 and 2.7 for the median and pectoral fins, respectively) compared well to inferred thrust values determined from particle-image velocimetry (PIV) wake measurements (2.2-2.4 and 2.7-2.9). Caudal fin mean theoretical thrust was not significantly different from measured (PIV) values (n = 24, P > 0.05), implying no momentum enhancement. Pectoral-fin thrust was half that of the median and caudal fins due to high fin-jet angles, low circulation and momentum. Average total fin thrust and fish drag were not significantly different (n = 24, P > 0.05). Vortex rings generated by the fins were elliptical, with size dependent on fin chord and stroke amplitude. Hydrodynamic advantages (thrust enhancement at no cost to hydrodynamic efficiency, reduction of side forces minimizing energy wasting yawing motions and body drag) are probably common among rigid-bodied organisms propelled by undulatory fins. A trade-off between momentum enhancement and the rate of momentum generation (thrust force) sets a practical limit to the former. For small fins whilst momentum enhancement is high, absolute thrust is low. In addition, previously suggested limitations on thrust enhancement set by reductions in propulsive force associated with progressive reductions in fin wavelength are found to be biologically unrealistic.     

Molecular dynamics simulation of fluid properties by the streamwise oscillation of the solid wall

In this paper, the hydrodynamics of streamwise wall oscillations on a Couette flow are studied using the molecular dynamics method. Firstly, based on the two-dimensional Couette flow model which is made up of copper wall and argon fluid, the characters of the fluid near the streamwise oscillation wall are simulated under the condition of varied oscillating parameters. By scrupulous data processing, some significative results such as the velocity distribution, the density distribution, the potential energy curves of the flow field and the frictional force of the wall are obtained. Secondly, the mechanism how the wall oscillation brings about change to the frictional drag at liquid–solid interface is investigated. And the results indicate that the frictional drag can be reduced significantly by applying appropriate streamwise oscillation to the solid wall. The drag reduction rate mainly depends on the oscillation parameters. In addition, the decrease in the fluid’s density near the wall is another important reason behind the frictional drag reduction.     

Refolding of proteins from inclusion bodies is favored by a diminished hydrophobic effect at elevated pressures

The application of high hydrostatic pressure is an effective tool to promote dissolution and refolding of protein from aggregates and inclusion bodies while minimizing reaggregation. In this study we explored the mechanism of high-pressure protein refolding by quantitatively assessing the magnitude of the protein-protein interactions both at atmospheric and elevated pressures for T4 lysozyme, in solutions containing various amounts of guanidinium hydrochloride. At atmospheric pressure, the protein- protein interactions are most attractive at moderate guanidinium hydrochloride concentrations (approximately 1-2 molar), as indicated by a minimum in B(22) values. In contrast, at a pressure of 1,000 bar no minimum in B(22) values is observed, indicating that high pressures colloidally stabilize protein against aggregation. Finally, experimental values of refractive index increments as a function of pressure indicate that at high pressures, wetting of the hydrophobic surfaces is favored, resulting in a reduction of the hydrophobic effect. This reduction in the hydrophobic effect reduces the driving force for aggregation of (partially) unfolded protein.     

On hydrodynamics of drag and lift of the human arm

The work presents results on drag and lift measurement conducted in a low speed wind tunnel on a replica of the entire human arm. The selected model positions were identical to those during purely rotational front crawl stroke in quasi-static conditions. A computational fluid dynamics model using Fluent showed close correspondence with the experimental results and confirmed the suitability of low speed wind tunnel for the drag and lift measurement in quasi-static conditions. The obtained profiles of the hydrodynamic forces were similar to the dynamic data presented in an earlier study suggesting that shape drag is a major contributing factor in propulsive force generation. The aim of this study was to underline the importance of the entire arm analysis, the elbow angle and a newly defined angle of attack representing the angle of shoulder rotation. It was found that both the maximum value of the drag force at 160 degrees elbow flexion angle and the momentum generated by it exceed the respective magnitudes for the fully extended arm. The latter is underlined by a prolonged plateau of near maximum drag that was obtained at shoulder angle range of 50-140 degrees suggesting that optimal arm configuration in terms of propulsive force generation requires elbow flexion. Furthermore it was found that drag trend is not consistent with the widely assumed and used sinus wave profile. A gap in the existing experimental research was filled as for the first time the entire arm lift and drag was measured across the entire stroke range.     

Tangent Resistance of Soil on Moldboard and the Mechanism of Resistance Reduction of Bionic Moldboard

The tangent resistance on the interface of the soil-moldboard is an important component of the resistance to moving soil . We developed simplified mechanical models to analyze this resistance. We found that it is composed of two components, the frictional and adhesive resistances. These two components originate from the soil pore, which induced a capillary suction effect, and the soil-moldboard contact area produced tangent adhesive resistance. These two components varied differently with soil moisture. Thus we predicted that resistance reduction against soil exerted on the non-smooth bionic moldboard is mainly due to the elimination of capillary suction and the reduction of physical-chemical adsorption of soil.     

Anti-adhesive Property of Maize Leaf Surface Related with Temperature and Humidity

The anti-adhesive surfaces have always aroused great interest of worldwide scientists and engineers.But in practical applications,it often faces the threat and impact of temperature and humidity.In this work,the excellent anti-adhesive performance of maize leaf under high temperature and humidity were investigated in detail.Firstly,the adhesion forces of the maize leaf surface under different temperature and humidity were measured by using Atomic Force Microscopy (AFM).The temperature of the substrate was varied between 23 ℃ to 100 ℃,and the ambient relative humidity is from 18％ to 100％.It was found that the adhesion force of maize leaf decreased with the increase of temperature and humidity.The mechanism of its excellent anti-adhesive performance of maize leaf under high temperature and relative humidity was revealed.The transverse and longitudinal ridges on maize leaf surface interlace with each other,forming small air pockets,which reduces the actual contact area between the object and the maize leaf.With the increase of humidity,the liquid film will be formed in the air pockets gradually and so much water vapor is produced with increase of temperature.Then the air flow rate increases though the wavy top of transverse ridges,inducing the dramatic decrease of adhesion force.Inspired by this mechanism,four samples with this bionic structure were made.This functional "biomimetic structure" would have potential value in the wide medical equipments such as high frequency electric knife with anti-adhesion surface under high temperature and high humidity.     

Storm Resistant Boat Designing Based on the Geometry and Movement of Water Strider

A novel conceptual model of boat is developed based on the bionic properties of water strider. This four-legged model is called storm resistance boat. Concentrated balancing forces, asymmetry of arms and smooth motion against waves and the effect of arms length on the reduction of drag and effects of wave are the major characteristics of water strider which are considered for designing this model. The results indicate the characteristic improvement of the small boat and its resistance against strong waves as well as marine ill-conditions. This boat can be considered as a high speed rescue boat in marine traffic.