运用多媒体进行流体力学教学的体会

本文介绍北京大学力学系在本科生流体力学课程中运用多媒体进行教学的情况和学生的反映．作者体会到：多媒体教学应该是常规教学的一种精彩的补充，但是不应该、也不能够完全代替常规教学．那些难以用语言描述的动态物理图像，采用多媒体演示的效果最好；播放的内容一定要严格精选，灵活使用，力求紧密配合教学大纲；要把多媒体教学与其它教学手段有机地结合起来，取长补短，相辅相成     

把小微元分析法的教学贯彻流体力学课程的始终

 小微元分析法是流体力学最重要的基本功之一, 用该法求解流体 力学问题具有概念清晰、 过程简洁等优点. 因此, 在教学中应将该方 法贯彻全课程的始终, 并不断加以深化, 使学生学会从物理本质上简化 问题, 建立合理的力学模型.     

Solution for the oscillation of a newtonian fluid in a co-axial viscometer

When one cup of a co-axial viscometer oscillates,the measured moment on theother(stationary)cup shows a phase lag,partly due to the inertial effect of the fluidwithin the gap between the cups.In this paper such an effect is illustrated by a newexact solution of the Navier-Stokes equation,which is derived herein by a scheme ofreducing it to a two-point boundary value problem for ODEs,Our numerical resultsindicate that,as the Womersley number a or the dimensionless gap widthδincreases,the fluid velocity profile within the gap gradually deviates from the linear one andtransits to that of the boundary layer type,with the result that the moment decreasesin the magnitude and lags behind in the phase.With the advantage of high accuracyand excellent stability,the scheme proposed herein can readily be extended to solveother linear periodic problems.     

Lubrication analysis of a cell sliding into a circular pore

The resistance to the blood cells at the entrance to capillaries and membrane pores contributes considerably to the peripheral resistance in the blood circulation. This paper proposes, for the first time, a simplified mechanical model in an attempt to treat the axisymmetric motion of a cell sliding into a circular pore. In this model, the shape of the cell is taken as given according to the microvideograph and the cell membrane is assumed to slide over its surface. The lubrication theory is applied to the thin layers of plasma between the membrane and the pore wall, yielding the pressure and shear stress distributions over the membrane as well as the resultant drag exerted on the cell. Our computations have simulated the process of the cell entering the pore, which is in qualitative agreement with the microvideographic observations.The Project Supported by National Natural Science Foundation of China.The authors wish to express their thanks to Professor S. Weinbaum of The City University of New York for his enlightening suggestions on the mechanical model of this problem during his visit to Peking University. The authors are also grateful to Professor Li Gui-shan of Institute of blood. The Chinese Academy of Medical Sciences, for providing the relevant microvideographes.     

脑动静脉畸形供血动脉内压力测量准确性的分析

对脑动静脉畸形供血动脉内压力测量的准确性进行了定量的分析,分析结果认为,以介入导管方法测量脑动脉畸形患者供血动脉内压力时,导管的影响可以导致测量结果偏低,这一结论支持了脑动静脉畸形患者低压灌注的程度一般不易于导致部分脑组织缺血的观点。     

我怎样讲授边界层概念

本概述作在本科生流体力学课程中讲授边界层概念的体会：一方面通过实例反复阐明雷诺数极限下在物面附近引入边界层概念的必要性;另一方面通过反复练习培养学生掌握量阶分析方法。     

Theoretical analysis of using airflow to purge residual water in an inclined pipe

ＩｎｔｒｏｄｕｃｔｉｏｎＰｕｒｇｉｎｇｒｅｓｉｄｕａｌｌｉｑｕｉｄｉｎａＵ＿ｓｈａｐｅｄｐｉｐｅｌｉｎｅｉｓｃｈａｌｌｅｎｇｅｆｏｒｃｈｅｍｉｃａｌａｎｄｔｒａｎｓｐｏｒｔａｔｉｏｎｉｎｄｕｓｔｒｙ[1].Ｍａｎｙｔｅｃｈｎｉｑｕｅｓｈａｖｅｂｅｅｎｅｍｐｌｏｙｅｄｔｏｐｕｒｇｅｏｕｔｒｅｓｉｄｕａｌｗａｔｅｒ[2 ],ｂｕｔｎｏｎｅｈａｖｅｂｅｅｎｃｏｍｐｌｅｔｅｌｙｓａｔｉｓｆａｃｔｏｒｙ .Ｏｎｅｐｏｓｓｉｂｌｅｍｅｔｈｏｄｆｏｒｄｏｉｎｇｔｈｉｓｈａｓｂｅｅｎｔｏｂｌｏｗａｇｒｅａｔｑｕａｎｔｉｔ…     

气流排除倾斜管道积水的理论分析

运用作者推导的动量积分关系式,分析了向有积水的斜置管道中分别吹入轴向气流和螺旋气流时积水的运动情况。结果表明:在大多数情况下,螺旋气流能除去斜置管道中积水;而轴向气流不能除去积水,一段时间后会出现逆流。这一结果与Horii和赵耀华等人在这个问题上所做的实验结果一致。此外,还讨论了不同的初始条件对排水情况的影响。     

第1届世界生物力学大会预告

<正> 会议由国际指导委员会组织,东道主是美国生物力学全国委员会。内容涉及生物力学的所有方面,包括实验,临床,体育医学和理论等,学科领域有:心血管力学;肌肉骨骼力学;矫形学;细胞的性质与能动性;运动力学;创伤研究;血液流变学;应力与生长的相互作用;牙科力学;步态分析;组织工程;微循环;软组织流变学;肌肉力学;分子力学。      

圆孔外Stokes流中球形粒子的运动*

在研究悬浮液入孔问题时,粒子在孔外任意位置所受的力和力矩是所需的最基本数据.本文在严宗毅等(1987)算出的有限个离散数据的基础上.首次给出了球在圆孔外的全部十二个力和力矩系数的近似解析表达式.我们应用这些系数计算零雷诺数下球形粒子入孔时的轨道和旋转角速度,结果与现有实验数据完全一致.分析不同系数的相对重要性表明,在孔口和孔壁附近不能忽略旋转效应.在靠近孔口边缘的局部区域必须计及侧向力效应.以往的理论结果在孔口附近与实验不符,正是由于忽略了这些因素.本文还详细讨论了粒子和孔口尺寸的相对大小以及重力和浮力对于粒子运动轨道、速度分布和旋转的影响,指出用大粒子做中性悬浮实验时,对其密度的要求特别严格.本文所提供的力和力矩系数,考虑因素全面、比较准确,便于计算,为进一步研究各种涉及粒子入口的问题提供了良好的前提.