Regularity of Stationary Weak Solutions in the Theory of Generalized Newtonian Fluids with Energy Transfer

In this paper, we prove regularity results for weak solutions to some stationary problems arising in the theory of generalized Newtonian fluids with energy transfer. Namely, we prove that these solutions are strong. In the two-dimensional case, we prove the Hölder continuity of the first gradient of a solution. Bibliography: 30 titles.     

Estimates of Deviations for Generalized Newtonian Fluids

The paper is concerned with estimates of deviations from exact solutions for stationary models of viscous incompressible fluids. It is shown that if a function compared with exact solution is subject to the incompressibility condition, then the deviation majorant consists of terms that penalize the inaccuracy in the equilibrium equation and the rheological relation defined by a ceratin dissipative potential. If such a function does not satisfy the incompressibility condition, then the majorant includes an additional term. The factor of this term depends on the constant in the Ladyzhenskaya–Babuka–Brezzi condition. Bibliography: 27 titles.     

Numerical Modelling of Newtonian and Non-Newtonian Fluids Flow

The work deals with numerical modelling of 2D/3D laminar incompressible viscous flows for Newtonian and non–Newtonian fluids. The unsteady system of Navier–Stokes equations with steady boundary conditions in the form of an artificial compressibility method is solved by multistage Runge–Kutta finite volume method. Steady state solution is achieved for t→∞. Convergence is followed by steady residual behaviour. For unsteady solution high compressibility coefficient β² is considered. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

非牛顿粘性不可压流方程的近似惯性流形

本文利用对非牛顿粘性不可压缩流方程对时间 t的解析性和长时间渐近性估计 ,具体构造了它的近似惯性流形 ,并得出收敛阶估计 .     

Verification of Linear (In)Dependence in Finite Precision Arithmetic

We present theoretical background for verification of linear dependence/independence of columns of a matrix by means of finite precision arithmetic.     

Formulation of Quantum Scattering Theory in Terms of Proper Differentials (Stationary Wave Packets)

Constructing the basic operators of scattering theory on and off the mass shell in terms of spatially bounded stationary wave packets or proper differentials is described. For this, we use a technique based on a certain scheme for discretizing the continuum. Finite-dimensional approximations for the Green's functions and T-matrix, which are first found here, are immediately constructed for any energy using a single simple diagonalization of the Hamiltonian matrix in an L ₂-type complete basis. We show that the developed approach leads to a convenient finite-dimensional representation of the scattering operators in the basis of the wave functions of a harmonic oscillator. The method allows an immediate extension to the problem of three and more bodies.     

Mathematical Theory of Fluids in Motion

The goal of this paper is to present the recent development of mathematical fluid dynamics in the framework of classical continuum mechanics phenomenological models. In particular, we discuss the Navier–Stokes (viscous) and the Euler (inviscid) systems modeling the motion of a compressible fluid. The theory is developed from fundamental physical principles, the necessary mathematical tools introduced at the moment when needed. In particular, we discuss various concepts of solutions and their relevance in applications. Particular interest is devoted to well-posedness of the initial-value problems and their approximations including possibly certain numerical schemes.     

微极流体润滑在径向轴承中应用

本文从微极流体场方程出发,在润滑层的通常假设下,把它化简为两个独立的常微分方程组,并求得速度、微转动角速度的解析表达式.推导了微极流体润滑的雷诺方程,把它应用于有限长径向轴承的求解.通过数值计算得到了微极效应对各种动力参数、几何参数下轴承的压力分布、承载力、流量系数和摩擦系数的影响,并析了它的实际意义,使微极流体理论应用到工程问题又接近了一步.     

Theory and Application of Characteristic Finite Element Domain Decomposition Procedures for Coupled System of Dynamics of Fluids in Porous Media

For a coupled system of multiplayer dynamics of fluids in porous media,the characteristic finiteelement domain decomposition procedures applicable to parallel arithmetic are put forward.Techniques suchas calculus of variations,domain decomposition,characteristic method,negative norm estimate,energy methodand the theory of prior estimates are adopted.Optimal order estimates in L~2 norm are derived for the error inthe approximate solution.     

Theory of Non-Equilibrium Stationary States as a Theory of Resonances

We study a small quantum system (e.g., a simplified model for an atom or molecule) interacting with two bosonic or fermionic reservoirs (say, photon or phonon fields). We show that the combined system has a family of stationary states parametrized by two numbers, T ₁ and T ₂ (‘reservoir temperatures’). If T ₁ ≠ T ₂, then these states are non-equilibrium stationary states (NESS). In the latter case we show that they have nonvanishing heat fluxes and positive entropy production and are dynamically asymptotically stable. The latter means that the evolution with an initial condition, normal with respect to any state where the reservoirs are in equilibria at temperatures T ₁ and T ₂, converges to the corresponding NESS. Our results are valid for the temperatures satisfying the bound min (T ₁,T ₂) > g ^{2 + α}, where g is the coupling constant and 0 < α < 1 is a power related to the infra-red behaviour of the coupling functions. Submitted: March 20, 2006. Revised: March 19, 2007. Accepted: May 11, 2007. Marco Merkli: Partly supported by an NSERC PDF, the Institute of Theoretical Physics of ETH Zürich, Switzerland, the Departments of Mathematics of McGill University and the University of Toronto, Canada. Matthias Mück: Supported by DAAD under grant HSP III. Israel Michael Sigal: Supported by NSERC under grant NA7901.     

Some Converse Theorems in Newtonian Field Theory and Their Applications

Two converse theorems related to a family of homogeneous homothetic bodies and connected to the theory of the Newtonian field are proved. In both of them the function characterising the attraction is unknown and it is demonstrated that this function in the first theorem is given by the one characterising the Newtonian field and in the second theorem it is given by this latter function with the addition of a linear function of distance. A second unknown function appears in the second theorem and it is proved that it is a linear function of the volume of the bodies. Moreover, in both the theorems it is proved that the unknown shape of the bodies must be spherical.

The conjecture is made that the two theorems are still true without the hypothesis that the unknown function characterising the attraction has a pole.

The full significance of the two theorems is briefly illustrated by the application of the second theorem to the case of a finite homogeneous fluid, the behaviour of which is isotropic with respect to an element of it. Among other results, it is found that the shape of the fluid is necessarily spherical and the forces at a distance which are exerted among the elements of the fluid are expressed by Newton's Law of gravitation.

AMS Classification 31B20, 31B99, 76A02, 76A99     

On the Theory of KM2O-Langevin Equations for Stationary Flows (2): Construction Theorem

The aim of the present paper is to construct the KM₂O-Langevin matrix LM([X,Y]) directly from the correlation matrix function R by using (DDT), (FDT) and (PAC) as an algorithm.     

On the lnviscid Theory of Rotating Fluids

Conservation theorems for “energy” and mean circulation in an inviscid rotating fluid are stated in their most general forms (which do not presume the existence of inertial modes). The geostrophic motion that contains all the mean circulation of an initial velocity field is identified as the time average of the flow. A preliminary study of the in viscid motion inside a closed cone reveals many singular features and indicates that the inertial wave spectrum may be continuous.     

Simulation of Jet Flows in Ideal Fluids by Variable Finite Elements

A free-boundary problem involved in computation of the shapeof a jet of an ideal fluid exiting through an orifice is formulatedas finding a stationary point of a certain functional definedon a variable domain. The stationary point of the functionaldiscretized in terms of linear finite elements is then locatednumerically by using the Newton-Raphson procedure. This numericalapproach is much faster than the previous attempts; it can accuratelyreproduce the exact results known for planar jet flows whenthe orifice is an infinite slit; and it can easily be appliedto the computation of axisymmetric jets.     

Existence for a Class of Non-Newtonian Fluids with a Nonlocal Friction Boundary Condition

We deal with a variational inequality describing the motion of incompressible fluids, whose viscous stress tensors belong to the subdifferential of a functional at the point given by the symmetric part of the velocity gradient, with a nonlocal friction condition on a part of the boundary obtained by a generalized mollification of the stresses. We establish an existence result of a solution to the nonlocal friction problem for this class of non-Newtonian flows. The result is based on the Faedo-Galerkin and Moreau Yosida methods, the duality theory of convex analysis and the Tychonov-Kakutani-Glicksberg fixed point theorem for multi-valued mappings in an appropriate functional space framework.     

完美路图P3（G）

P_k（G）是指这样的图：G中的所有k路作为P_k（G）的顶点集，两个不同的顶点在Pk（G）中邻接当且仅当它们所对应的两条k路的并为G中的（k＋1）路或k圈，那么，完美图猜想对于路图P_3（G）是成立的．     

A Duality Method in Prediction Theory of Multivariate Stationary Sequences

Let W be an integrable positive Hermitian q × q–matrix valued function on the dual group of a discrete abelian group G such that W^–1 is integrable. Generalizing results of T. Nakazi [N] and of A. G. Miamee and M. Pourahmadi [MiP] for q = 1 we establish a correspondence between trigonometric approximation problems in L²(W) and certain approximation problems in L²(W^–1). The result is applied to prediction problems for q–variate stationary processes over G , inparticular, to the case G = ℤ.     

定态微扰论的一种处理新方法

利用渐近方法,直接由Ｌａｇｒａｎｇｅ常数变易法求解含微扰项的Ｓｔｕｒｍ－Ｌｉｏｕｖｉｌｅ本征值问题．最后举一实例证明,与传统的展开法（结果为无穷多项）相比较,两种方法完全一致,等价,适用范围也相同,而且本文所述方法简明（一般只含两项）更具有一定的物理意义