Coupling Bionics For Functional Surface Of Drag And Noise Reduction Based On Pigeon Body Surface

Supported by the National Key Grant Program of Basic(Grant No. 2002CCA01200),the National High Technology Research and Development Program of China (Grant No.2003AA305080) and the National Natural Science Foundation of China (Grant No.50635030),this paper mainly deals with bionic drag and noise reduction which are based on the biology coupling theory and non-smooth theory and whose study object is pigeon body surface.The research is mainly carried out following:original shape,the design of bionic model,the flow of the surface simulation analysis and bionic experiment.With the development of economy,energy crisis and environmental pollution have become two major urgent problems that need to be solved,which have caused the global attention.Bionic drag and noise reduction is the practical engineering application of coupling characteristics of the body surface of the typical biology, which possesses the function of lower drag and noise than others.Bionic drag and noise reduction is one of the green environment protection and effective methods.All the different function of biology in the nature can realize the optimal adaptation to the environment through different systematic characteristic coupling.The non-smooth of biology body surface is a natural phenomenon existing commonly in the biologic world.The non-smooth structure of the body surface of biology makes biology have functions of reducing adhesion,drag reduction,noise reduction and wear-resisting.The excellent performance of these functions provides explore space and biology model to bionic design.The main purpose of this research is to study coupling bionic drag and noise reduction.Based on the morphology of pigeon body surface, this paper carries out surface design of coupling bionic, which regards flying animal pigeon as research object.It undergoes numerical simulation analysis on air-solid surface of coupling surface.And the bionic drag and noise reduction functional surface experiment is done.First the quantified bionic information of the breast,back and wing is acquired and the morphology of these parts is studied.The stereoscopic microscope (XTJ130) is used to carry out research into the morphology of pigeon surface.The pigeon body surface presents microscopic non-smooth structure.According to the research,the lengthways shape of the pigeon non-smooth surface appears regular undulant structure,which can be considered as continuous arch ripple non-smooth surface.The surface of the feather presents non-smooth structure of riblet.The three-dimensional information of pigeon surface scanned based on 3D LASER SCANNER SYSTEM are utilized to obtain geometric model of the surface of the breast,back and wing of the pigeon using CopyCAD software.The feather is the non-smooth unit of the surface,whose different unit parameters are analyzed and so are the parameters of arrangement density of feathers and the distances between the feathers etc.The feather is proximately considered as ellipsoid coronal.The average height of the ellipsoid coronal is 0.801cm.The average values of long semiaxis and short semiaxis of the bottom projection are 1.744cm and 1.125cm.The average distance of horizontal distance between feathers of the breast and back are 0.492cm and 0.425cm.The average distance of vertical distance between feathers of the breast and back are 0.751cm and 0.827cm.The feather is the unit of body surface.The mathematical model of the unit and conjunction relationship is built.And the simulation of the surface is done using the program.The fractal dimension of the surface of the different parts of the body is calculated according to the three-dimensional information of the surface obtained from the laser scanner.The average values of the surfacial fractal dimension of the three parts are 2.92938,2.93604 and 2.95852.The surfaces of the back,breast and wing respectively present fractal characteristic.The fractal dimension of the surface of the different parts is calculated according to the image obtained from the stereoscopic microscope.The average values of the fractal dimension of the three parts are 1.8049,1.804686 and 1.9415.There is not only micro non-smooth structure on pigeon surface, but function of the surface is the result of coupling effect of some factors.The morphology,tail of tile structure , the arrange manner and the flexible material of the feather , the microstructure morphology of the surface and the microcosmic non-smoothed structure construct of coupling system structure of pigeon surface.The configuration element of the surface has greatest influence on drag reduction.Next is influence of structure element on drag reduction.Others are general coupling element.In air medium, the seven kinds of coupling functional surface models (shape and structure) are designed whose carrier is flat.Four kinds of representative coupling bionic surface(feather flute,ellipse convex,ellipse concave and riblet)are mainly selected.The software of FLUENT6.2 is used to make analyses on numerical simulation of the flow compared with smooth surface.The Computing Flow Dynamics analyses using the RANS equations with RSM turbulence model were performed to investigate the effect of the bionic coupling surface.The cuboid calculation domains are built.The smooth surface and the coupling surface are put on the above and undersurface respectively in the cuboid.The result of numerical simulation indicates that the coupling bionic surface can reduce the wall shear stress and Reynolds stress.The skin friction drag is reduced.When velocity of flow is 20m/s,the drag of ellipse concave surface will decrease by 8.28%,the drag of feather flute surface will decrease by 3.6%,the drag of ellipse convex surface will decrease by 8.89%,the drag of ellipse concave surface will decrease by 7.46%.In the same flow,the flow direction and motion state of the air of the coupling functional surface have some change.The speed of the flow of the coupling functional surface is less than the smooth surface.The thickness of the boundary layer is greater than the smooth surface.So the radical reason of coupling surface drag reduction lies in effectively control or amend of boundary layer.Layered stacking bionic coupling films,which present the structure and shape of coupling functional surface,are designed.The coupling bionic surface is used on the ABSTRACT blade of cooling fan and thirteen coupling bionic fans are designed and processed.The experiment and research show that 70% of the thirteen fans realize drag reduction in all conditions with maximum of 28%,the others realize drag reduction in some rotate speed.The average rate of torque reduction of feather flute surface,ellipse convex surface,ellipse concave surface and riblet surface is 11.8%,5.0%,5.3%,5.9% and 12.8% respectively.Only flute surface fan of all fans realize noise reduction in all conditions with most of noise reduction by 2.05dB.Multi-factor and multi-objective comprehensive evaluation is done considering drag,noise,air volume,efficiency and so on.The evaluation equation is R=b4RM+ b3RA + b2 R? + b1RV (b4=0.4,b3= 0.3,b2= b1=0.15).The evaluation result of the bionic fans is that FS08 presents optimal performance.Each performance of FS07 and FS09 is next to it. It has been found in the experiment that the materials of the blade surface influent the drag and noise performance of fan.The different distribution of coupling functional surface in blade is also one of the factors that influence the performance of fan.The technology of drag reducing and noise lowering is critical technology of flow mechanism design.The research into drag and noise of fan has universality and representation on drag and noise of the engineering.The study result can offer foundation of the theory and practice the design and exploitation of blade,impeller, aerofoil of the propeller-driven aircraft and so on.The research of coupling bionic surface lays foundation for the development of bionic drag and noise reduction,producing active influence on study bottleneck of drag reduction and noise reduction in air or other flow medium,and widening the bionic engineering research methods.The research also has broad engineering application prospects.