原始变量时间推进法计算封闭腔内自然对流换热

发展了一种原始变量时间推进数值方法,对求解域采用非等距交错网格剖分,对方程组各项的离散,是利用泰勒级数于网格点展开取二阶精度进行,对压力及压力修正的求解,则是采用SIMPLE方法进行。 将该数值方法应用于封闭方腔层流自然对流换热的计算,对不同瑞利数（Ra）条件下的数值试验显示,该数值方法物理概念清晰,计算稳定,计算结果精度高。     

NUMERICAL SIMULATION OF FLOWS FOR SECOND-ORDER VISCOELASTIC FLUID COUPLED WITH HEAT TRANSFER BY DIFFERENTIAL QUADRATURE METHOD

The problem of two-dimensional steady flow of an incompressible second-order viscoelastic fluid coupled with heat transfer between parallel plates was considered. A viscous dissipation function was included in the energy equation.When the elastic property of the fluid is weaker, the zerothorder and first-order approximate governing equations were obtained by means of the perturbation method. To understand the behavior of flow near the tube wall, the half-domain was divided into two sub-domains, in which one is a thin layer near the wall called the inner domain and the remainder is called the outer domain. The governing equations in the inner domain and in the outer domain were discretized respectively by using the Differential Quadrature Method (DQM). The matching conditions at the interface between the inner and outer domains were presented. An iterative method for solving these discretized equations was given in this paper. The numerical results obtained agree with existing results.     

NUMERICAL SIMULATIONS OF NONLINEAR WAVE TRANSFORMATION AROUND WAVE-PERMEABLE STRUCTURE

1.INTRODUCTION Thedevelopmentofbreakwaterdesignmeth odologyoftenrequireaconditionofpermittingfor protectionofecosystem,itisalsoanalternativeto massivegravitybreakwatersinreductionofwave transmissioninshallowwater.Thetheoreticalso lutionsofwavepermeablebreakwatersdiversified indifferentexpressionsoftheenergydamping term,duetolaminarandturbulentflowintheper meablestructures.Theporositysolution[1]isbased onatrialmethod,andanumberofauthorssolve theproblembydifferentnumericalapproach[27].Inpre…     

Increasing risk: Dynamic mean-preserving spreads

We extend the celebrated Rothschild and Stiglitz (1970) definition of Mean-Preserving Spreads to a dynamic framework. We adapt the original integral conditions to transition probability densities, and give sufficient conditions for their satisfaction. We then focus on a class of nonlinear scalar diffusion processes, the super-diffusive ballistic process, and prove that it satisfies the integral conditions. We further prove that this class is unique among Brownian bridges. This class of processes can be generated by a random superposition of linear Markov processes with constant drifts. This exceptionally simple representation enables us to systematically revisit, by means of the properties of dynamic mean-preserving spreads, workhorse economic models originally based on White Gaussian Noise. A selection of four examples is presented and explicitly solved.     

Boussinesq方程的二阶椭圆余弦驻波解

等深浅水域中的流体运动可由Boussinesq方程描述。众所周知,该方程有行进波解（孤立波及椭圆余弦波）。本文则以Boussinesq方程为控制方程,利用渐近匹配法对椭圆余弦波在直墙上反射进行研究,给出了反射过程中内、外场波形及速度变化的解析表达,从而得到了Boussinesq方程的二阶椭圆余弦驻波型的解析解,并讨论了这类驻波的若干性质。当波长无限增大时,所得解析解收敛于孤立波的情况。这些解析结果不仅有助于揭示岸坡对非线性浅水波影响的力学机理,在海岸防护和开发和岸壁附近结构物的设计条件等工程领域中也具有现实的指导意义。     

On irregular functionals of SDEs and the Euler scheme

We prove a sharp upper bound for the error $\mathbb {E}|g(X)-g(\hat{X})|^{p}We prove a sharp upper bound for the error in terms of moments of , where X and are random variables and the function g is a function of bounded variation. We apply the results to the approximation of a solution to a stochastic differential equation at time T by the Euler scheme, and show that the approximation of the payoff of the binary option has asymptotically sharp strong convergence rate 1/2. This has consequences for multilevel Monte Carlo methods. The author was supported by the Finnish Graduate School in Stochastics and Statistics, the Ellen and Artturi Nyyss?nen Foundation, and the Academy of Finland, project #110599.     

消力池池深的简化计算法

通过对池深水力计算相关方程组进行数学变换,采用优化拟合的方法,以标准剩余差最小为目标函数,在工程实用范围内,经逐次逼近拟合获得了可直接进行方程组联立求解、最大相对误差小于2.8％的近似公式(其中相对误差小于1.0％的计算点占总点数的84％),具有一定的推广意义.     

NUMERICAL STUDY OF SOLITARY WAVE FISSION OVER AN UNDERWATER STEP

Solitary wave fission over an underwater step is numerically investigated. The numerical model is based on the enhanced Boussinesq equations, which appropriately represent both the nonlinearity and dispersivity of surface water waves. The finite difference method defined on the staggered grid in space with an implicit scheme for time stepping is employed for the numerical solution of the governing equations. It is demonstrated that Boussinesq type equations, though they are vertically integrated, can describe the details of the solitary wave fission process with very good accuracy. Numerical results of the reflected and transmitting wave heights, the number of solitons emitted from the transmitting wave and their amplitudes all agree very well with the analytical solution derived from KdV equation by virtue of a linear long wave approximation in the vicinity of the underwater step.     

PRESSURE DISTRIBUTION DETERMINED BY USING MEASURED VELOCITY FIELD DATA AND RANS EQUATIONS

The current paper presents the result of a study on determining the pressure distribution along the surface of a foil section by using measured velocity field data and the Reynolds Averaged Navier-Stokes equations. The results are compared with the measured pressure data and show its satisfaction. It is a try to find a new way to determine pressure by combining the experimental data and CFD method.