运用周期性边界条件预报螺旋桨的敞水性能(英文)

Mathematical models of propellers were created that investigate the influence of periodic boundary conditions on predictions of a propeller’s performance. Thrust and torque coefficients corresponding to different advance coefficients of DTMB 4119, 4382, and 4384 propellers were calculated. The pressure coefficient distribution of the DTMB 4119 propeller at different sections was also physically tested. Comparisons indicated good agreement between the results of experiments and the simulation. It showed that the periodic boundary condition can be used to rationally predict the open water performance of a propeller. By analyzing the three established modes for the computation, it was shown that using the spline curve method to divide the grids can meet the calculation’s demands for precision better than using the rake cutting method.     

Asymptotical Properties for Parabolic Systems of Neutral Type

Asymptotical properties for the solutions of neutral parabolic systems with Robin boundary conditions were analyzed by rising the inequality analysis. The oscillations problems for the neutral parabolic systems were considered and some oscillation criteria for the systems were established.     

Research on an Algorithm of Shape from Shading

Shape from shading(SFS)is an important domain in computer vision. The paper presented an improved algorithm of shape from shading based on a single image according to an existed one. The presented algorithm enhanced the boundary constraints to eliminate the rotation distortion on the border of reconstructed object and introduced the factor of brightness error to weaken the influence irradiance equation‘s nonlinearity on reconstructed errors. The reconstructed results verify the performance improvement in terms of accuracy by the input image of a synthetic image and a real image of weld.     

The Singularly Perturbed Problem for Nonlinear Nonlocal Reaction Diffusion Systems

IntroductionRecently the nonlinear singularly perturbedproblem has been investigated in the internationalacademic circles[1] .Approximation methods havebeen developed and refined,including the methodof averaging,boudary layer method,matchedasymptotic expa…     

单跳激励下水工高性能面板时空效应舒适度性态研究

基于国内外舒适度研究现状与评价标准,提出了一种利用Dirac Delta函数来表征水工高性能面板时空分布的舒适度研究方法。通过建立改进单跳激励模型（HJ-CDLEM）,求解得到水工高性能面板模型的激励响应机理方程,提出同时考虑时间效应和结构空间效应的水工高性能面板舒适度性态评价指标,并以此开展了舒适度性态评估,揭示了激励作用在该种水工结构中的响应传播特性与空间分布特征。     

Banach空间中含有间断项的一阶周期边值问题整体解的存在唯一性

利用半序方法,只用上解或下解得到Banach空间中含有间断项的常微分方程一阶周期边值问题在[0,a]（a〉0）上整体解的两个存在唯一性结果,这两个结果是独立的新结论．     

汽车风洞试验中的雷诺数、阻塞和边界层效应问题综述

对汽车风洞试验中的雷诺数、阻塞和边界层效应进行了分析并得出若干结论:首先,采用缩比模型时,雷诺数将对气动力测量产生影响,雷诺数过低通常会使阻力系数测量值偏大约1%～2%,而更低的局部雷诺数甚至会改变局部气流特性;其次,有限的风洞尺寸必然产生阻塞效应,它影响气动力和试验参考风速的测量,但可以通过适当的经验方法和合理的标定程序进行修正;最后,风洞固定地板产生的边界层会干扰车辆底部和车轮附近的气流.如果没有任何边界层控制措施,气动阻力测量值会偏小,而升力测量值偏大;且底盘越低误差越大,因此须采取合理的控制方案以降低边界层对气动力测量的影响.     

柔性层状路面应力和位移场的边界元分析

为研究任意形状分布的各种荷载作用下柔性多层弹性路面应力和位移的性状分布特点,利用层状材料的广义Kelvin基本解,建立了边界元分析方法.结合广义Kelvin基本解与边界元方法,建立柔性层状路面边值问题的边界积分方程,对于核函数中出现的奇异积分做了解答.该方程中不舍在层状材料交界面上的积分,可求解任意形状分布各种荷载作用下的多层弹性体系应力和位移.算例分析表明:该方法可以获得较高的计算精度;由于采用了层状材料的广义Kelvin基本解,该方法能处理力学参数沿深度方向任意变化的柔性路面.     

局部蠕变损伤的细观定义与量测

研究了CH169高温合金蠕度损伤的非均匀性。通过蠕变损伤的金相微观分析,定义 了空洞损伤变量和显微硬度损伤变量,给出了两种变量间的关系式,按提出的细观蠕 度损伤定义建立了单轴局部蝠变损伤模型,分析表明,新模型有较好的预测能力。      

Numerical Investigation on Two-dimensional Boundary Layer Flow with Transition

As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics （CFD）. A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation （RANS） in this paper. Turbulence model plays a significant role in the complex flows＇ simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox （2006） k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition＇s behavior.