【作者】 孙明礼；

【导师】 杨庆新； 李德才；

【作者基本信息】 北京交通大学 ， 机械设计及理论， 2008， 博士

【摘要】 粘性减阻一直是科学工作者进行研究的一个热门领域,之所以如此,是因为粘性减阻有着广泛的实际应用和重要的学术价值。磁性液体粘性减阻具有结构简单、可控性好、寿命长、使用范围广等优点,是一种新型粘性减阻方法。本论文的工作有实验、理论和数值模拟三个部分。在实验方面,制备了高饱和磁化强度的水基及煤油基磁性液体;设计了保持磁性液体涂层稳定性的减阻结构,并通过磁性液体涂层的破坏性实验来观察磁性液体涂层的变形、稳定和破坏过程,确定了使磁性液体涂层与所输运液体保持界面动力稳定的条件;通过磁性液体涂层对管道流量影响的实验,验证了磁性液体涂层厚度在减阻过程中存在一个最佳值,在此一厚度减阻效果最好;在设计的减阻实验台上进行磁性液体粘性减阻实验,获得了减阻效率为5.5%～9.5%的减阻效果,确定了磁性液体涂层的表面积与减阻效果之间的关系,确定了被输运粘性液体的入口速度与减阻效果之间的关系。在理论研究方面,指出磁性液体涂层内部存在回流现象,推导出磁性液体涂层内速度分布的解析式。在数值模拟部分,应用ANSYS软件对减阻结构的磁路设计、粘性液体层流进行了磁场、流场的数值模拟。为观察磁性液体涂层的运动状态,设计了磁性液体管道流动的数学模型。将实测的磁性液体磁化强度曲线通过函数最佳逼近的方法拟合成一个反正切函数。将磁性液体磁化强度和体积力公式带入Navier-Stokes方程,进行磁场与流场的耦合,并将耦合方程导入Comsol Multiphysics软件,对入口速度为半波正弦函数的磁性液体管道流动进行分析。获得磁性液体在磁场体积力的作用下,一部分磁性液体被吸附在管壁不动或以很小速度流动,造成此处的过流面积减小,使中间部位磁性液体速度增加,但当入口速度为零时,受磁场体积力的作用处,磁性液体的运动并没有停止,而是有激烈的涡旋运动。更多还原

【Abstract】 Drag reduction is always a popular field in science research.The reason lies in that it has the wide applications and important academic merits.Magnetic fluid viscosity drag reduction is a new type of drag reduction method which has so many advantages as simple structure,exeeUent controllablility,long life,far using range, etc.The work of this paper is focused on experiment,theory and numerical simulation of drag reduction research.In the part of experiment,Kerosene-based & water-based magnetic fluid are prepared and drag reduction structure which can keep magnetic fluid coat stabilization is designed.At meanwhile,the process of magnetic fluid coat distortion,stabilization & breakage are observed by magnetic fluid coat breakage experiment,so the condition of interface stabilization between magnetic fluid and viscosity fluid is confirmed.Optimal thickness of magnetic fluid coat is validated in the course of drag reduction by coat influence flux experiment.The effect of drag reduction is improved by 5.5%～9.5% during the magnetic fluid viscosity drag reduction experiment is fulfilled on the self-designed test-bed.The relationship between surface area of magnetic fluid coat and the effect of drag reduction is confirmed,and the relationship between the entrance velocity of viscosity fluid and the effect of drag reduction is confirmed.In the part of theory,circumfluence phenomenon inside magnetic fluid coat is confirmed.Analytic formula of velocity inside magnetic fluid coat is deducted.In the part of numerical simulation,magnetic-circuit of drag reduction strcture and viscosity fluid laminar flow are analysed within magnetic field and flow field by ANSYS finite element software.Math-model of magnetic fluid flow in the pipeline is designed in order to observe motion state of magnetic fluid coat.The measurement result of magnetization curve of magnetic fluid is fitted in an anti-tangent function by function optimum- approach method.Magnetic field and flow field are coupled by substituting magnetic fluid magnetization-strength & vol-force function into Navier-Stokes function.The entrance velocity of magnetic fluid flowing in the pipeline with half-sine wave function is analysed by coupling function and written into Comsol Multiphysics software.The results show that a part of magnetic fuid are adsorbed by pipeline wall,or slowed down by the magnetic vol-force on the mgnetic fluid which brings out decreasing fluid flowing area and increasing velocity of magnetic fluid on the middle part.Motion of magnetic fluid is agitated rather than stopped in local eddies by the magnetic vol-forces which is working on the magnetic fluid,even though the entrance velocity of magnetic fluid is zero.There are 92 figures,16 tables,112 references on this paper.更多还原