广义Oldroyd-B流体作MHD旋转流动时的精确解

对充满多孔空间的广义Oldroyd-B流体,研究有滑移时磁流体动力学（MHD）的旋转流动．数学建模时采用了分式积分法．给出平板振荡和周期性压力梯度诱导的3个示例,并得到了每种情况下的精确解．比较了有滑移和没有滑移条件下两种情况的结果．曲线图表表明,滑移对速度分布的影响是巨大的．     

Exact Solutions for Steady Capillary Waves on a Fluid Annulus

Summary. Exact solutions for steady capillary waves on an annulus of swirling irrotational fluid are presented. The solutions have an intimate mathematical connection with the finite amplitude waves on fluid sheets identified by Kinnersley [8]. This mathematical connection is made explicit by first retrieving the solutions of Kinnersley using an extension of a new approach to free surface potential flows with capillarity recently devised by the present author (Crowdy [3]). A much-simplified representation of Kinnersley's original solutions results from the reformulation. The method is then generalized to identify the exact solutions for steady capillary waves on an annulus. Received February 9, 1998; revised November 5, 1998     

Pulselike Exact Solutions for a Model Describing Nerve Fibers

A quasi-linear nonhomogeneous first order hyperbolic system describing nerve pulse transmission is considered. By requiring the compatibility of the governing equations with quasi-linear differential constraints, exact solutions to the model in question are determined. Furthermore classes of material response functions amenable to the mathematical approach are characterized. Initial and/or boundary value problems of interest in nerve pulse propagation are solved. It is proved that the governing model admits solutions which describe a space clamp situation and the propagation of a localized action potential pulse along the nerve.     

Exact Traveling-Wave Solutions for Model Geophysical Systems

Exact traveling-wave solutions of time-dependent nonlinear inhomogeneous PDEs, describing several model systems in geophysical fluid dynamics, are found. The reduced nonlinear ODEs are treated as systems of linear algebraic equations in the derivatives. A variety of solutions are found, depending on the rank of the algebraic systems. The geophysical systems include acoustic gravity waves, inertial waves, and Rossby waves. The solutions describe waves which are, in general, either periodic or monoclinic. The present approach is compared with the earlier one due to Grundland (1974) for finding exact solutions of inhomogeneous systems of nonlinear PDEs.     

微分约束方法在求解二阶流体精确解上的应用

利用微分约束方法研究了二阶流体的精确解,通过使用一阶微分约束条件,不仅获得了具有抽吸作用下的Couette和Poiseuille平行流、碰撞射流、平面拉伸流等具有明确物理意义的流动解,而且获得了两类新的精确解,所得精确解表明二阶流体的流动特性不仅依赖于物质粘性参数,而且依赖物质弹性参数.此外讨论了部分边值问题.     

考虑二次梯度项影响的非线性不稳定渗流问题的精确解

考虑了二次梯度项影响的非线性径向流动问题的无限大地层和有界地层渗流模型．在井底定流量和定压生产时,对无限大地层及有界地层(包括封闭和定压地层)六种情况,利用广义Weber变换和广义Hankel变换求得了实空间的解析解,分析了非线性压力解与线性压力解的差异,发现在晚时段其差异可达8%以上．因此在试井长时要考虑二次梯度项的影响．     

On One Method for Constructing Exact Solutions of Nonlinear Equations of Mathematical Physics

Doklady Mathematics - A new method for constructing exact solutions of nonlinear equations of mathematical physics is proposed. The method is based on nonlinear integral transformations in...     

一个描述血吸虫病的数学模型的周期解

研究一个描述血吸虫病的周期微分方程模型dx/dt=-rx+A/S(t)y,dy/dt=-δ(t)y+B(S(t)-y) x2/1+ x.数值计算发现该系统同时具有渐近稳定的零解和一个正周期解.通过证明该系统解的有界性,并在一个函数空间上构造单调有界序列,进而证明了在一定条件下正周期解的存在性.     

不对称柔性壁管道内幂律流体蠕动传输的精确解

在不对称管道内,研究了壁面柔曲性对非Newton流体蠕动流的影响.流变学性质由幂律流体本构方程表征.在数学表达中,采用了长波和低Reynolds数近似.得到了流函数和速度的精确解.给出了流线图及其俘获现象.对所讨论的流动,陈列了关键参数的显著特征,并最后给出了主要结论.     

A Few Exact Solutions for the Model of Equal Spin-Spin Interactions

For the model of equal spin-spin interactions, we obtain exact Heisenberg expressions for the spin operator components and use them to find the relations that hold for spin operators appearing in the thermodynamic mean. We use the obtained exact relations for the means to describe the thermodynamics of the model under consideration. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 145, No. 3, pp. 411–419, December, 2005.     

New Exact Solutions of One Nonlinear Equation in Mathematical Biology and Their Properties

The classical Lie approach and the method of additional generating conditions are applied to constructing multiparameter families of exact solutions of the generalized Fisher equation, which is a simplification of the known coupled reaction–diffusion system describing spatial segregation of interacting species. The exact solutions are applied to solving nonlinear boundary-value problems with zero Neumann conditions. A comparison of the analytic results and the corresponding numerical calculations shows the importance of the exact solutions obtained for the solution of the generalized Fisher equation.     

应用改进的简单方程法求非线性数学物理方程的精确解

应用改进的简单方程法求得Cahn-Allen方程和Jimbo-Miwa方程的精确解,这些解包括双曲函数解、三角函数解.当对双曲函数解中的参数取特殊值时,可以得到了孤立波解.当对三角函数解中的参数取特殊值时,可以得到对应的周期波函数解.实践证明,简单方程法对于研究非线性数学物理方程具有非常广泛的应用意义.     

Exact Solutions to a Finite-difference Model of a Nonlinear Reaction-advection Equation: Implications for Numerical Analysis

This article gives exact solutions to a finite-difference model of a nonlinear reaction-advection equation. We show that this partial difference equation and the corresponding stationary and spatially independent difference equations derived from this model give the best representation of the original partial differential equation. The relevance of this work to the elimination of chaotic behavior in numerical solutions of differential equations is discussed.     

对流流体中表面波的非线性发展方程的显式精确行波解

该文用直接代数方法和假设方法的一种结合得到了对流流体中表面波的非线性发展方程u     

Mathematical Analysis of a Transport Model with Unbounded Heat Capacities

We consider a problem of nuclear waste contamination in the basement. We derive a detailed model describing the simultaneous transport of brine, radionuclides and heat in a compressible flow through a porous medium. It leads to a nonlinear system of fully coupled partial differential equations. Using a fixed point approach, we prove existence of physically relevant weak solutions.      

一类反应扩散方程的精确解

运用首次积分法并借助计算机符号计算系统Mathematica得到了一类非线性反应扩散方程u_t-u_(xx) au βu~2 γu~3=0的精确解,其中既包括已知的类孤立波解,又有新的精确解.     

The Existence of Global Solutions to a Fluid Dynamic Model for Materials for Korteweg Type

We discuss the existence of global solutions to a fluid dynamic model for materials of Korteweg type, and discuss the three dimensional nonisothermal motion. The higher order derivatives of density in the constitutive relation makes it necessary to introduce an interstitial working term in the energy equation. This makes the energy estimate more involved. Nevertheless, it is possible to show the existence of global solutions by the euergy method.     

流变学流体的蠕动传输:食道中食物块的运动模型

研究食道中蠕动传输的流体力学.对任意的波形和任意的管道长度,建立起流变学流体蠕动传输的数学模型.用粘性流体的Ostwald-de Waele幂定律,描述非Newton流体的流动特性.解析公式化模型,详细且精确地给出食物块在食道中蠕动传输相关的一些重要性质.分析中应用了润滑理论,本研究特别适合于Reynolds数不大的情况.将食道看作环形的管道,通过食道壁周期性的收缩来传输食物块.就单个波和周期性收缩一组波的传播,研究与传输过程有关变量的变化,如压力、流速、食物颗粒轨迹以及流量等.局部压力的变化,对流变指数n有着高度的敏感性.研究结果清晰地表明,食物块在食道中蠕动传输时,Newton流体或流变学流体构成的连续流体,以组合波传播比大间隔单波传播,传输效率要高得多.     

RLW—Burgers方程的精确解

借助未知函数的变换，ＲＬＷ－Ｂｕｒｇｅｒｓ方程和ＫｄＶ－Ｂｕｒｇｅｒｓ方程化为易于求解的齐次形式的方程，从而得到ＲＬＷ－Ｂｕｒｇｅｒｓ方程和ＫｄＶ－Ｂｕｒｇｅｒｓ方程的精确解。