凹坑形仿生非光滑表面的减阻性能研究
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摘要
本文基于工程仿生学研究的基本方法,将动物表面信息抽象为凹坑形仿生非光滑形态,建立了仿生非光滑表面模型,计算了多个速度下该非光滑表面的减阻效果并对其减阻机理进行了研究。
传统的减阻研究主要采用风洞实验方法,但是它耗资大、实验条件控制困难,为了缩短开发周期,降低成本,本文用数值计算的方法,对凹坑形非光滑表面流场进行细微的研究,探讨其减阻机理,研究凹坑单元尺寸和来流速度对减阻效果的影响,为设计出更加有效的非光滑形态提供理论依据。
本文共设计了4种不同尺寸的凹坑非光滑形态,对不同来流速度下的多种流场进行了模拟。首先确定凹坑形单元的结构和尺寸,采用四面体的非结构网格对模型进行离散化处理,满足了各个表面的网格划分要求。在数学模型上,选用标准k-ε湍流模型使N-S方程封闭:为了精确地计算壁面附近的流场,近壁面区采用低雷诺数下的的标准k-ε模型;运用二阶迎风格式保证了运算的精度。通过比较凹坑形非光滑表面和光滑表面湍流边界层的流动特性,对凹坑形表面的减阻机理进行研究。
通过计算,本文得到了如下定性及定量的结论:(1)与光滑表面相比,凹坑非光滑表面上的压差阻力略微增大,但是摩擦阻力得到了很大程度的降低,故总阻力降低;(2)凹坑高径比为0.5的情况下,凹坑直径为0.8mm的非光滑表面比直径为1.0mm的表面具有更好的减阻效果,最高减阻率为7.20%;(3)凹坑直径为0.8mm时,凹坑高径比对减阻效果影响不大,各个模型的最大减阻率都达到了7%以上;(4)对非光滑表面边界层内的流场进行了研究,发现凹坑单元能改变边界层的厚度以及边界层内的一些物理量的特性,达到减小阻力的作用;(5)绘制出凹坑内部的流线图和速度矢量图,发现来流与光滑表面之间是固-气两相界面,而非光滑表面上的凹坑单元使得来流气体与凹坑内部的低速气体形成气-气接触,这样能改变其边界层内的流场,大大降低摩擦阻力,达到减阻的效果。
Based on the essential bionic research method and combined with engineering, a simple non-smooth shape, dimple, is obtained by abstracting non-smooth surface information of the animal surfaces. The model is created to calculate the drag reduction effect of the dimple non-smooth surface in several velocities and to analyze the cause of drag reduction.
Because of the high expense and the difficulty to do experiments and in order to shorten the time of research, the method of numerical simulation is used instead of the wind tunnel experiment ways to simulate the flow of some surfaces, explore the theory of drag reduction and the influence of dimple size on drag reduction effect, which would provide academic support to design more effective dimple shapes.
Four dimple bionic non-smooth surfaces are designed and simulated and each of the four models are simulated in seven different velocities. After figuring out the model and the size of dimples, use tetrahedron unstructured grid to dispose the model to fill the mesh requires. As for the mathematical model, standard k-εturbulent model and low Re k-εmodel are applied. In order to get the exact result, the second order upwind format is used to discrete the mathematical model. Based on the results of simulation, the flow of boundary layer on both non-smooth surface and smooth surface are presented to discuss the drag reduction quality of dimple shape structure and to study the theory of drag reduction deeply.
Through a lot of calculation, the qualitative and quantitative conclusions are as follows:(1) Compared with smooth surface, the dimple non-smooth surface has a little higher pressure resistance but has a much lower viscous friction resistance, which leads to a reduction on total resistance. (2) When the diameter of the dimple is twice larger as the height, the non-smooth surfaces which have dimple structures with a diameter of 0.8mm have a much better performance on drag reduction than those which have dimple structures with a diameter of 1.0mm. (3) Under the premises that the diameter of all the dimples is 0.8mm, it proves that the height seems to have little influence on the resistance reduction effect. Each of the models simulated has a good drag reduction effect. (4) The flow inside the boundary layer is studied. It is found that the dimples on the unsmooth surface are able to change the thickness and some other aspects of the boundary layer, which leads to a drag reduction on dimple unsmooth surface. (5) The path lines and velocity vectors inside the dimples are depicted. It is found that as there is solid-fluid boundary between the coming fluid and smooth surface, unsmooth structure makes flows slow down inside the dimples. When air flows through dimple unsmooth surfaces, higher speed flows contact with some lower speed flows that exist in unsmooth structures, which would be able to change the flows inside the boundary of unsmooth surfaces, reduce the friction resistance and lead to a drag reduction.
传统的减阻研究主要采用风洞实验方法,但是它耗资大、实验条件控制困难,为了缩短开发周期,降低成本,本文用数值计算的方法,对凹坑形非光滑表面流场进行细微的研究,探讨其减阻机理,研究凹坑单元尺寸和来流速度对减阻效果的影响,为设计出更加有效的非光滑形态提供理论依据。
本文共设计了4种不同尺寸的凹坑非光滑形态,对不同来流速度下的多种流场进行了模拟。首先确定凹坑形单元的结构和尺寸,采用四面体的非结构网格对模型进行离散化处理,满足了各个表面的网格划分要求。在数学模型上,选用标准k-ε湍流模型使N-S方程封闭:为了精确地计算壁面附近的流场,近壁面区采用低雷诺数下的的标准k-ε模型;运用二阶迎风格式保证了运算的精度。通过比较凹坑形非光滑表面和光滑表面湍流边界层的流动特性,对凹坑形表面的减阻机理进行研究。
通过计算,本文得到了如下定性及定量的结论:(1)与光滑表面相比,凹坑非光滑表面上的压差阻力略微增大,但是摩擦阻力得到了很大程度的降低,故总阻力降低;(2)凹坑高径比为0.5的情况下,凹坑直径为0.8mm的非光滑表面比直径为1.0mm的表面具有更好的减阻效果,最高减阻率为7.20%;(3)凹坑直径为0.8mm时,凹坑高径比对减阻效果影响不大,各个模型的最大减阻率都达到了7%以上;(4)对非光滑表面边界层内的流场进行了研究,发现凹坑单元能改变边界层的厚度以及边界层内的一些物理量的特性,达到减小阻力的作用;(5)绘制出凹坑内部的流线图和速度矢量图,发现来流与光滑表面之间是固-气两相界面,而非光滑表面上的凹坑单元使得来流气体与凹坑内部的低速气体形成气-气接触,这样能改变其边界层内的流场,大大降低摩擦阻力,达到减阻的效果。
Based on the essential bionic research method and combined with engineering, a simple non-smooth shape, dimple, is obtained by abstracting non-smooth surface information of the animal surfaces. The model is created to calculate the drag reduction effect of the dimple non-smooth surface in several velocities and to analyze the cause of drag reduction.
Because of the high expense and the difficulty to do experiments and in order to shorten the time of research, the method of numerical simulation is used instead of the wind tunnel experiment ways to simulate the flow of some surfaces, explore the theory of drag reduction and the influence of dimple size on drag reduction effect, which would provide academic support to design more effective dimple shapes.
Four dimple bionic non-smooth surfaces are designed and simulated and each of the four models are simulated in seven different velocities. After figuring out the model and the size of dimples, use tetrahedron unstructured grid to dispose the model to fill the mesh requires. As for the mathematical model, standard k-εturbulent model and low Re k-εmodel are applied. In order to get the exact result, the second order upwind format is used to discrete the mathematical model. Based on the results of simulation, the flow of boundary layer on both non-smooth surface and smooth surface are presented to discuss the drag reduction quality of dimple shape structure and to study the theory of drag reduction deeply.
Through a lot of calculation, the qualitative and quantitative conclusions are as follows:(1) Compared with smooth surface, the dimple non-smooth surface has a little higher pressure resistance but has a much lower viscous friction resistance, which leads to a reduction on total resistance. (2) When the diameter of the dimple is twice larger as the height, the non-smooth surfaces which have dimple structures with a diameter of 0.8mm have a much better performance on drag reduction than those which have dimple structures with a diameter of 1.0mm. (3) Under the premises that the diameter of all the dimples is 0.8mm, it proves that the height seems to have little influence on the resistance reduction effect. Each of the models simulated has a good drag reduction effect. (4) The flow inside the boundary layer is studied. It is found that the dimples on the unsmooth surface are able to change the thickness and some other aspects of the boundary layer, which leads to a drag reduction on dimple unsmooth surface. (5) The path lines and velocity vectors inside the dimples are depicted. It is found that as there is solid-fluid boundary between the coming fluid and smooth surface, unsmooth structure makes flows slow down inside the dimples. When air flows through dimple unsmooth surfaces, higher speed flows contact with some lower speed flows that exist in unsmooth structures, which would be able to change the flows inside the boundary of unsmooth surfaces, reduce the friction resistance and lead to a drag reduction.
引文
[1]Robert JP.Drag reduction:an industrial challenge.Special Course on Skin Friction Drag Reduction,AGARD Report 786,1992.
[2]田军,薛群基.平板上低表面能涂层的水筒减阻研究.科学通报,1996,4l(18):1667-1669
[3]Toms B A.Some observation on the flow of linear polymer solution through straight tubes at large Reynolds numbers.Proc.1st Intern Rheol.Congr.Scheveningen(Holland),1948,135-137.
[4]Merkle C L,Pal S,Deutsch S.Bubble characteristics and trajectories in a microbble boundary layer.Physics of Fluids,1988,31(4):330-351
[5]Madavan N K,Deutsch S,Merkle C L.Reduction of turbulent skin friction by microbubbles.Physics of Fluids,1984,27(2):356-363
[6]纪永波.磁减阻技术研究.石油工业,1994,4(5):46-48
[7]Gray J.Studies in animal locomotion.Ⅵ.The propulsive powers of the dolphin.J Exp Biol,1936,13:192-199.
[8]Kramer MO.Boundary layer stabilization by distributed damping.J Am Soc Naval Eng(Feb),1960,p 25-33.
[9]Carpenter PW.Status of transition delay using compliant walls.In:Bushneli DM,Hefner JN(eds)Viscous drag reduction in boundary layers.Progress in astronautics and aeronautics,1990,123.AIAA,Washington.
[10]Walsh MJ.Turbulent Boundary Layer Drag Reduction Using Riblets.AIAAPaper.1982:82-0169
[11]Walsh MJ.Riblets a as Viscous Drag Reduction Technique.AIAA Journal.1983,21(4):485-486
[12]Walsh MJ,Lindemann AM.Optimization and Application of Riblets for Turbulent Drag Reduction.AIAA Paper.1984:0347
[13]Walsh MJ.Riblets in Viscous Drag Reduction in Boundary Layers.Progress in Astronautics and Areonautics.1990,123:203-61
[14]王晋军,兰世隆,苗福友,沟槽面湍流边界层减阻特性研究,空气动力学报,2001,42(4):1-4
[15]Jin-Jun Wang,Shi-long Lan,Guang Chen.Experimental Study on the Turbulent Boundary Layer.Fluid Dynamics Research.2000,27:217-219
[16]Bacher E V,Smith C R.A combined visualization-anemometry study of the turbulent drag reducing mechanisms of triangular micro-groove surface modifications AIAA,1985,85-0548
[17]Gallagher J A,Thomas A S W.Turbulent boundary layer characteristics over stream wise grooves,AIAA,1984,84-2185
[18]Coustols E.Behavior of Internal Manipulators:"Riblet" Models in Subsonic and Transonic Flows.AIAA.1989:89-0963
[19]Park S R,Wa turbulent boundary layer,AIAA Journal,1994,32(1):31-38
[20]李育斌,乔志德.运七飞机外表面沟纹膜减阻的试验研究.气动力试验与测量控制.1995,9(3):21-26
[21]石秀华,宋保维,包云平.条纹薄膜减小湍流阻力的实验研究.水动力学研究与进展,1996,11(5):546-552
[22]傅慧萍,石秀华,乔志德.条纹薄膜减阻特性的数值分析.西北工业大学学报,1999,17(1):19-24
[23]宫武旗等.沟槽壁面减阻机理实验研究.工程热物理学报.vol.23.No.5,spe,2002
[24]王晋军,兰世隆,陈光.沟槽面湍流边界层结构实验研究.力学学报,2000,32(5):621-626
[25]王晋军,陈光.沟槽面湍流边界层近壁区拟序结构试验研究.航空学报,2001,22(5):400-405
[26]王晋军,李亚臣.沟槽面三角翼减阻特性实验研究.空气动力学学报,2001,19(3):283-287
[27]Bearman P W,Harvey J K.Control of Circular Cylinder Flow by the Use of Dimples.AIAA J,1993,31:1753-1756
[28]杨弘炜,高歌.一种新型边界层控制技术应用于湍流减阻的实验研究,航空学报,1997,18(4):455-457.125
[29]S.J.Lee,S.H.Lee.Flow field analysis of turbulent boundary layer overariblet surface.Experiment in Fluids.2001,30:153-166.
[30]Robinson S K.Coherent motions in the turbulent boundary layer.Annual Review of Fluid Mechanics.1991,23:601-639.
[31]Starling L,Choi K S.Nonlinerar laminar turbulent transition over riblets.In Proceedings of the Laminar Flow work shop,Queen Mary and Westifield College,London,1997.
[32]Bechert DW,Bartenwerfer M,Hoppe G.Turbulent drag reduction by nonplanar surfaces-a survey on the research at TU/DLR Berlin.Structure of Turbulence and Drag Reduction IUTAM Symposium Zurich/Switzerland,1989:525-523
[33]Paolo Luchini,Fernando Manzo,Amilcare Pozzi.Resistance of a grooved surface to parallel flow and cross-flow.J.Fluid Mech,1991,228:87-109
[34]Changhai Zhou,Rui Zhang,Luquan Ren.Bionic Analysis in the Surface Morphology of Cybister Bengalensis.Proceeding of CIJR International Conference.Beijing,2004,Oct.11-14,2004.
[35]张成纯.旋成体仿生非光滑表面流场控制减阻研究(博士论文).长春:吉林大学,2007
[36]王福军.计算流体动力学分析.清华大学出版社,2004年
[37]吴子牛.计算流体力学基本原理.科学出版社,2000:1-173.
[38]Choi K S,Orchard D,Turbulent management using riblets for heat and momentum transfer.Thermal Fluid Sci,1997,15:109-124
[39]陈汉平.计算流体力学.北京:水利电力出版社,1995年,第一版。
[40]Dean R B.Reynolds number dependence of skin friction and other bulk flow variables in two-dimensional rectangular duct flow.J.Fluids Eng,1978,100:215-223.
[41]Moser R D,Kim J,Mansour N N.Direct numerical simulation of turbulent channel flow up to Re=590.Phys.Fluids A 1999,11(4):943-945.
[42]张成春,任露泉,王晶.旋成体仿生凹环表面减阻的试验分析及数值模拟.吉林大学学报(工学版),2007,37(1):100-105
[2]田军,薛群基.平板上低表面能涂层的水筒减阻研究.科学通报,1996,4l(18):1667-1669
[3]Toms B A.Some observation on the flow of linear polymer solution through straight tubes at large Reynolds numbers.Proc.1st Intern Rheol.Congr.Scheveningen(Holland),1948,135-137.
[4]Merkle C L,Pal S,Deutsch S.Bubble characteristics and trajectories in a microbble boundary layer.Physics of Fluids,1988,31(4):330-351
[5]Madavan N K,Deutsch S,Merkle C L.Reduction of turbulent skin friction by microbubbles.Physics of Fluids,1984,27(2):356-363
[6]纪永波.磁减阻技术研究.石油工业,1994,4(5):46-48
[7]Gray J.Studies in animal locomotion.Ⅵ.The propulsive powers of the dolphin.J Exp Biol,1936,13:192-199.
[8]Kramer MO.Boundary layer stabilization by distributed damping.J Am Soc Naval Eng(Feb),1960,p 25-33.
[9]Carpenter PW.Status of transition delay using compliant walls.In:Bushneli DM,Hefner JN(eds)Viscous drag reduction in boundary layers.Progress in astronautics and aeronautics,1990,123.AIAA,Washington.
[10]Walsh MJ.Turbulent Boundary Layer Drag Reduction Using Riblets.AIAAPaper.1982:82-0169
[11]Walsh MJ.Riblets a as Viscous Drag Reduction Technique.AIAA Journal.1983,21(4):485-486
[12]Walsh MJ,Lindemann AM.Optimization and Application of Riblets for Turbulent Drag Reduction.AIAA Paper.1984:0347
[13]Walsh MJ.Riblets in Viscous Drag Reduction in Boundary Layers.Progress in Astronautics and Areonautics.1990,123:203-61
[14]王晋军,兰世隆,苗福友,沟槽面湍流边界层减阻特性研究,空气动力学报,2001,42(4):1-4
[15]Jin-Jun Wang,Shi-long Lan,Guang Chen.Experimental Study on the Turbulent Boundary Layer.Fluid Dynamics Research.2000,27:217-219
[16]Bacher E V,Smith C R.A combined visualization-anemometry study of the turbulent drag reducing mechanisms of triangular micro-groove surface modifications AIAA,1985,85-0548
[17]Gallagher J A,Thomas A S W.Turbulent boundary layer characteristics over stream wise grooves,AIAA,1984,84-2185
[18]Coustols E.Behavior of Internal Manipulators:"Riblet" Models in Subsonic and Transonic Flows.AIAA.1989:89-0963
[19]Park S R,Wa turbulent boundary layer,AIAA Journal,1994,32(1):31-38
[20]李育斌,乔志德.运七飞机外表面沟纹膜减阻的试验研究.气动力试验与测量控制.1995,9(3):21-26
[21]石秀华,宋保维,包云平.条纹薄膜减小湍流阻力的实验研究.水动力学研究与进展,1996,11(5):546-552
[22]傅慧萍,石秀华,乔志德.条纹薄膜减阻特性的数值分析.西北工业大学学报,1999,17(1):19-24
[23]宫武旗等.沟槽壁面减阻机理实验研究.工程热物理学报.vol.23.No.5,spe,2002
[24]王晋军,兰世隆,陈光.沟槽面湍流边界层结构实验研究.力学学报,2000,32(5):621-626
[25]王晋军,陈光.沟槽面湍流边界层近壁区拟序结构试验研究.航空学报,2001,22(5):400-405
[26]王晋军,李亚臣.沟槽面三角翼减阻特性实验研究.空气动力学学报,2001,19(3):283-287
[27]Bearman P W,Harvey J K.Control of Circular Cylinder Flow by the Use of Dimples.AIAA J,1993,31:1753-1756
[28]杨弘炜,高歌.一种新型边界层控制技术应用于湍流减阻的实验研究,航空学报,1997,18(4):455-457.125
[29]S.J.Lee,S.H.Lee.Flow field analysis of turbulent boundary layer overariblet surface.Experiment in Fluids.2001,30:153-166.
[30]Robinson S K.Coherent motions in the turbulent boundary layer.Annual Review of Fluid Mechanics.1991,23:601-639.
[31]Starling L,Choi K S.Nonlinerar laminar turbulent transition over riblets.In Proceedings of the Laminar Flow work shop,Queen Mary and Westifield College,London,1997.
[32]Bechert DW,Bartenwerfer M,Hoppe G.Turbulent drag reduction by nonplanar surfaces-a survey on the research at TU/DLR Berlin.Structure of Turbulence and Drag Reduction IUTAM Symposium Zurich/Switzerland,1989:525-523
[33]Paolo Luchini,Fernando Manzo,Amilcare Pozzi.Resistance of a grooved surface to parallel flow and cross-flow.J.Fluid Mech,1991,228:87-109
[34]Changhai Zhou,Rui Zhang,Luquan Ren.Bionic Analysis in the Surface Morphology of Cybister Bengalensis.Proceeding of CIJR International Conference.Beijing,2004,Oct.11-14,2004.
[35]张成纯.旋成体仿生非光滑表面流场控制减阻研究(博士论文).长春:吉林大学,2007
[36]王福军.计算流体动力学分析.清华大学出版社,2004年
[37]吴子牛.计算流体力学基本原理.科学出版社,2000:1-173.
[38]Choi K S,Orchard D,Turbulent management using riblets for heat and momentum transfer.Thermal Fluid Sci,1997,15:109-124
[39]陈汉平.计算流体力学.北京:水利电力出版社,1995年,第一版。
[40]Dean R B.Reynolds number dependence of skin friction and other bulk flow variables in two-dimensional rectangular duct flow.J.Fluids Eng,1978,100:215-223.
[41]Moser R D,Kim J,Mansour N N.Direct numerical simulation of turbulent channel flow up to Re=590.Phys.Fluids A 1999,11(4):943-945.
[42]张成春,任露泉,王晶.旋成体仿生凹环表面减阻的试验分析及数值模拟.吉林大学学报(工学版),2007,37(1):100-105