A CLOSED SYSTEM OF EQUATIONS FOR DENSE TWO-PHASE FLOW AND EXPRESSIONS OF SHEARING STRESS OF DISPERSED PHA’E AT A WALL

In this paper.each of the two phases in dense two-phase flow is considered ascontinuous medium and the fimdamental equations for two-phase flow are described inEulerian form.The generalized constitutive relation of the Bingham fluid is applied to thedispersed phase with the analysis of physical mechanism of of dense two-phase flow.Theshearing stress of dispersed phase at a wall is used to give a boundary condition.Then amathematical model for dense two-phase flow is obtained.In addition.the expressions ofshearing stress of dispersed phase at a wall is derived according to the fundamental,model ofthe frictional collision between dispersed-phase particles and the wall.     

表示湍流场的一种新设想

本文仿照量子场论中描述基本粒子产生湮灭的方法来描述湍流中涡旋的产生和消灭.因为当某一基本粒子存在的时候,我们可以认为它是一个不变实体,而湍流中涡旋则在时间过程中不断变化和耗散,所以在类比应用量子场论方法时首先要解决怎样的湍流涡旋可认为是同一个涡旋.根据线性化理论的特点,我们认为在时间过程中按相似性规律变化时湍流涡旋才算是同一个涡旋,而把不具有相似性的涡旋出现或消失,看成是方程(2.6)中相互作用项φ_i所引起的湮火和产生的结果.然后,我们采用和量子场论相类似的产生算符和消灭算符来描述湍流涡旋系统所处的状态.最后,我们利用原N-S方程中相互作用项来构成涡旋相互作用的“Schr?dinger”方程以描述其状态的变化.这样就得类似于量子场论的湍流涡旋相互作用理论.     

The double and triple velocity correlations of small vortexes in three-vortex model theory and the decay of grid-produced turbulence

In the three-vortex model theory of turbulence ^[1,2] and double and the triple velocity correlation functions of small vortexes were employed. In this paper, the double and the triple velocity correlation functions of small vortexes are further discussed, and the expressions of some coefficients in the expansions in terms of relative displacement of two points are given. Finally, by using these coefficients, the decay of grid-produced trubulence is calculated. The result of calculations gives good agreement with the experimental data of G.K. Batchelor and A.A.Townsend ^[3].The projects Supported by the National Natural Science Foundation of China.     

层状二维流动的基本方程式

在很多海洋、大气等二维流动问题中所用的动力学方程往往沿用推广后的河流水力学方程或"纳维-斯托克斯方程"其中把湍流阻力项写成这样的方程式和湍流阻力项用到实际问题上去,无疑是存在着极大的局限性,而将导致矛盾百出.本文则从雷诺方程出发,把所有的物理量沿深度加以平均,求出平均以后的物理量所满足的运动方程,连续方程和扩散方程.     

相似理论和泥沙的垂直分布

本文利用相似性原理处理了二维渠道均匀定常挟沙水流,在湍流脉动速度和含沙量涨落值相似的条件下,我们得到了泥沙垂直于挟沙水流的流动方向的含沙量分布.这个含沙量分布和扩散理论得到的含沙量分布略有差别,而和重力理论得到的含沙量分布则差别较大.     

热力学理论与空化现象

有关空化现象的理论研究大多建立在1917年由Rayleigh[1]开始的,后由Plesset等人发展起来的单个空泡运动理论的基础上.该理论仅从流体动力学的某些观点出发,考虑了力的作用,对诸如水下爆炸等问题的讨论,无疑是合适的.由于忽视了空泡生长或消失过程中气、液两相间的物质交换及能量转化,因此对空化现象的讨论则认为是不完备的. 本文主要从热力学观点.分析高速水流中的空化现象、空泡形成条件、空化数以及讨论空化模型实验的相似性问题.     

泥沙的群体沉降速度

本文讨论了在浓度很高时候,泥沙的群体沉降速度.作者认为所谓泥沙的群体沉降速度问题从物理本质来说并不是真正的沉降速度问题,而是水在泥沙和水所组成的胶团形成的多孔介质中的渗流问题,也就是水流经这种多孔介质所形成的问题.作者根据这样的认识,写出了泥沙群体沉降速度的数学表达式,并且和黄委会水科所测量得到的实验数据进行了比较.比较的结果是令人满意的.     

空化问题中的相变现象与接近平衡的速率

前文[9]我们已经说明用单个空泡的急剧膨胀和收缩来说明空化现象是不合适的.原因是空化现象中的实际气泡的变动与急剧膨胀和收缩的变化情形差距很大,而和平衡状态比较接近,本文紧接着前文[9]给出了气泡趋于平衡的速率和弛豫时间.并且给出空化现象中气泡可以作为平衡状态的判断准则.     

The fundamental equations of two-dimensional layer flows

In many studics on two-dimensional flows in field of atmosphere and ocean theequations which are extension of river-hydraulic equationsor Navier-Stokes equationsare usually used.In these equations stand forturbulent resistance.Obviously use of these equations in practice may lead to contradiction.In this paper the average of Reynolds equations over depth is taken.The motion equations,continuity equation and diffusion equation are obtained for the average physical variables.     

Fundamental equations of turbulent two-phase flow

A new set of Reynolds equations for predicting turbulent two-phase flows has been developed by means of Reynolds averaging method on the unsteady laminar equations of two-phase flow. These equations involve average terms of products of turbulent fluctuations in some physical parameters in a large degree. The interaction forces between two phases, the pressures for dispersed phase, extra stresses except for pressure and the expressions for energy interchange between two phases have been discussed.