环空套管内粘弹性流的解析解

本文讨论了二阶流体和 Maxwell流体在环形套管内的轴向不定常旋转运动 ,给出了与文 [1 ]不同形式的解析解 ,修正了该文的结果 .     

环空管内粘弹性流体不定常旋转流的解及流动特性分析

本文用Hankel积分变换法分别求得二阶流体和Maxwell流体在环管内不定常旋转流运动方程的解析解,据此可以分析环管内旋转速度和切应力的分布与变化特征;流体物性参数、管道环隙大小等参量在解析公式中有明确反映,便于定性分析和讨论,本解可以为钻探工程和高分子加工工艺的设计提供理论依据,另外还可用来分析双筒粘度计的流动状态和应力特征,拟合曲线,确定材料的粘弹性参数,在对这种流体进行特性分析时,我们发现,Maxwell流体的旋转流动在起动初期表现为方波振荡,振动的幅度和周期随Ha(物质常数)的增大而增大,此种现象还是首次发现,可能对实际应用有一定的意义。     

非牛顿流体偏心环空螺旋流的解析解

石油和化工中许多问题需要求解非牛顿流体偏心环空螺旋流。本文全面地研究了幂律流体和宾汉流体在偏心环空中层流螺旋流的流动规律与流动状态的判别。在理论上,根据流体力学原理,运用数学方法,在作者同心环空螺旋流的理论基础上,通过对偏心环空螺旋流流场的无限细分法,给出了该流场的视粘度分布、速度分布、流量和压降方程,进而建立了判别流态的稳定性参数。     

基于嵌套网格的环空流体内旋转杆柱与井筒碰撞特性研究北大核心CSCD

针对浸没在流体中杆管柱间相互接触问题,基于嵌套网格技术,该文建立了环空流体内旋转杆柱与井筒间碰撞的数值求解方法.将环空流体域分为相互嵌套的子区域:背景网格和组件网格,推导了各嵌套区域流场边界传递信息的插值计算公式,采用分域方法对环空流体域与杆柱固体域耦合进行求解.通过静止流体中球形颗粒与壁面正、斜碰撞实验对比,验证该文数值方法的正确性.研究了不同流体黏度、杆柱旋转速度条件下杆柱与井筒的碰撞特性,结果表明:1)杆柱与井筒碰撞的碰撞力、速度随黏度增大而降低,即杆柱与井筒碰撞的剧烈程度与流体黏度负相关;2)随着杆柱旋转速度增大,杆柱与井筒的碰撞力、速度也增大,即杆柱与井筒碰撞的剧烈程度与转速正相关.     

服从OldroydB型微分模型的粘弹性流体问题的数值解法

本文对服从OldroydB型微分模型的粘弹性流体问题给出了一种数值逼近算法．该算法对压力方程采用标准混合有限元方法,对速度方程采用并行非重叠区域分解方法和特征线法．这种并行算法在子区域上用Galerkin方法,通过积分平均方法显式地给出内边界的数值流．在本文最后还给出了该算法的最优L^2。一误差估计．     

粘弹性流体在渐缩毛管中渗流规律研究

驱油用聚合物溶液是粘弹性流体,当其在多孔介质中流动时由于拉伸变形会产生额外耗散,因此拉伸压降是不可忽略的.将Binding等人通过机械能平衡原理和最小能量原理建立的非牛顿流体入口收敛流动理论推广应用于渐缩毛管,并以幂指数关系表征剪切粘度与剪切速率关系、第一法向应力差与剪切速率关系、拉伸粘度与拉伸速率关系,从而建立了适用于描述粘弹性流体流动特性的渗流模型,分析了粘弹性流体在渐缩毛管中的渗流规律,利用建立的模型可以准确反映粘弹流体的渗流特性.     

粘弹性流体流经作依赖时间运动伸展面的三维流动及其传质问题

研究粘弹性流体流经伸展面时的三维边界层流动．假定伸展面的运动速度依赖于时间．进一步考虑了更高阶次化学反应对传质的影响．应用同伦分析法(HAM)进行计算．精确地分析了所得级数解的收敛性．用图形讨论了各参数变化对速度和浓度的影响．还给出了面传质数值的计算,将所得结果与前人的数值解进行了比较．     

考虑钻具接头影响的环空压耗计算

控压钻井是针对窄安全压力窗口现象所引起的勘探开发过程中的钻井难题所提出的,井筒压力分布的准确预测是保证控压钻井顺利实施的前提,为提高井筒压力的预测精度需准确计算环空摩阻压耗,应用量纲分析理论,综合考虑钻具接头、钻具旋转的影响,修正了环空摩阻压耗计算模型,提高了井筒压力的预测精度.模型研究表明:随着钻井液排量的增加,钻井液从层流变为紊流,局部摩阻压耗明显增加;且井越深,接头的累计压耗越大,接头对总摩阻压耗的贡献增加.随着钻具旋转速度的增加,环空压耗的增加或减少取决于惯性力与剪切稀释的共同作用.     

粘弹性二阶流体混合层流场拟序结构的数值研究

本文用拟谱方法对随时间发展的二维粘弹性二阶流体混合层流场进行了直接数据值模拟,给出在高雷诺数和低Deborah数下大涡的卷起、配对和合并等过程,通过与相同雷诺数下牛顿流体的比较,揭示了弱粘弹性对混合层中大涡拟序结构演变的影响.     

一维可压流体力学方程组整体经典解

本文研究了一维可压流体力学方程组的Cauchy问题,利用特征线法和分析的技巧,在一些合理的假设下,得到了Cauchy问题整体经典解存在的一个充分必要条件.     

BIFURCATION SOLUTIONS TO A BOUNDARYLAYER PROBLEM ARISING IN THE THEORY OF POWER LAW FLUIDS

1IntroductionandMainResultsThesingularnonlineartwthpointboundaryproblemllasbeenstudiedbyCallegariandFriedll1an[2]forp=1alldbyNacl1lliallalldCallegari[:]forp>1-Theydemonstratedtl1eexistellce,uniq11elless,al1da11alyticityofthepositivesolutiontotheproblem.Recently,Soewono,Vajravelu,andMol1apatra[']havecollsideredthesingulaxnonlineartwo-poiutboundaryvalueproble1llwllereCisagivenrealnulltherandh(x)isass1llnedtobeacolltinuousandincreasingfullctiondefinedon[-k, oo)satisfyingforsomepositivec0l1sta…     

THE ONE-DIMENSIONAL HUGHES MODEL FOR PEDESTRIAN FLOW: RIEMANN-TYPE SOLUTIONS

This paper deals with a coupled system consisting of a scalar conservation law and an eikonal equation,called the Hughes model.Introduced in [24],this model attempts to describe the motion of pedestria...     

多孔介质方程在一般几何流演化下的梯度估计

本文研究了多孔介质方程在一般几何流下的梯度估计.通过Aroson和Bénilan对多孔介质方程的研究结果以及运用Li-Yau梯度估计的方法,获得了对多孔介质方程的正解对于Laplace算子以及drifing Laplace算子在一般几何流演化下的一些梯度估计,推广了Zhu Xiao-bao和Deng Yi-hua的结果...     

环形域上半线性椭圆型方程径向正解的多重性

讨论如下的半线性方程：｛－△ｕ＝ｇ（│ｘ│）ｆ（ｕ） ｉｎΩ ｕ＝０ ｏｎδΩ这里Ω＝｛ｘ∈Ｒ＾Ｎ：Ｒ〈│ｘ│〈Ｒ｝ Ｎ≥２，０〈Ｒ〈Ｒ〈＋∞，在适当的条件下，运用变分方法我们得到了该方程存在两个非平凡径向正解。     

ON THE LOCAL WELL-POSEDNESS FOR THE DUMBBELL MODEL OF POLYMERIC FLUIDS

In this paper, we consider the local well-posedness of smooth solutions to a coupled microscopic-macroscopic model for polymeric fluid in general space dimension and with general initial data in Holder space.     

NUMERICAL ANALYSIS OF A FEM FOR A TRANSIENT VISCOELASTIC FLOW

We present the numerical analysis of a coupled method for the numerical simulation of transient viscoelastic flow obeying a differential constitutive equation with a Newtonian viscosity. The scheme used is based on Euler implicit method in time and maintains at each time step a couple of the velocity u and the viscoelastic part of the stress σ. Approximation in space is made by finite element method. The approximate stress, velocity and pressure are, respectively, P1-continuous, p2-continuous, and P1-continuous. Upwinding needed for convection of σ is made by a ““““Streamline Upwind Petrov Galerkin““““ method (SUPG).     

STRONG SOLUTIONS OF THE COUPLED NAVIER-STOKES-POISSON EQUATIONS FOR ISENTROPIC COMPRESSIBLE FLUIDS

In this article, we are concerned with the strong solutions of the coupled Navier-Stokes-Poisson equations for isentropic compressible fluids in a domain ΩR3. We prove the local existence of unique strong solutions provided that the initial data μ0 and μ0 satisfy a nature compatibility condition. The important point in this article is that we allow the initial vacuum: the initial density may vanish in an open subset of Ω. This is achieved by getting some uniform estimates and using a Schauder fixed point theorem.     

GLOBAL SOLUTIONS TO THE NAVIER-STOKES EQUATIONS FOR COMPRESSIBLE HEAT-CONDUCTING FLOW WITH SYMMETRY AND FREE BOUNDARY

ABSTRACT

Global solutions of the multidimensional Navier-Stokes equations for compressible heat-conducting flow are constructed, with spherically symmetric initial data of large oscillation between a static solid core and a free boundary connected to a surrounding vacuum state. The free boundary connects the compressible heat-conducting fluids to the vacuum state with free normal stress and zero normal heat flux. The fluids are initially assumed to fill with a finite volume and zero density at the free boundary, and with bounded positive density and temperature between the solid core and the initial position of the free boundary. One of the main features of this problem is the singularity of solutions near the free boundary. Our approach is to combine an effective difference scheme to construct approximate solutions with the energy methods and the pointwise estimate techniques to deal with the singularity of solutions near the free boundary and to obtain the bounded estimates of the solutions and the free boundary as time evolves. The convergence of the difference scheme is established. It is also proved that no vacuum develops between the solid core and the free boundary, and the free boundary expands with finite speed.