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排序方式: 共有179条查询结果,搜索用时 15 毫秒
81.
A molecular dynamics simulation is presented to calculate the Probability Distribution Functions (PDF) for the spatial positions and angular orientations of macromolecular rod-like particles in dilute solutions, under hydrodynamic flow, in the vicinity of uneven solid boundaries. The Brownian and hydrodynamic restitution model for ideally flat surfaces is generalized to simulate the diffusive collisions between the macromolecular particles and an uneven solid surface. Two types of uneven surfaces are particularly considered: the periodic grating and the random rough, with characteristic profiles of heights and lateral variations. Different from ideally flat surfaces, the simulation results demonstrate that uneven surfaces have characteristic depletion layers, and characteristic and variable PDF. This is the case under varying conditions of hydrodynamic flow, Brownian movement and diffusive collisions. These characteristics uniquely identify Boeder PDF signatures for the uneven surface topography. 相似文献
82.
李艳明 《吉林师范大学学报(自然科学版)》2012,(1):80-81,83
本文主要在孤立子理论及李群变换的指导下,运用函数变换的一些具体方法,配合计算软件maple的运算功能,求得了简化的Ostrovsky方程的一种显示解. 相似文献
83.
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85.
本文在α-混合严平稳过程的假设下,研究了条件概率密度核估计的偏和均方误差.在此基础上给出了核估计的渐近最优带宽,并以S&P500指数为例展示了本文的结果. 相似文献
86.
The difference between a presumed distribution of flamelet position and a numerically simulated distribution of distance function (a signed distance to flamelet) is investigated. It is shown that even if the distribution of flamelet position is symmetrical and close to Gaussian, the distribution of distance function away from the mean flame position is skewed towards the mean position and the mean of the distance function is also different from the distance to the mean position. The difference depends on the distance to the mean flame and the flame wrinkling amplitude. An extension method for the variance of the distance function and an upwind scheme for solving the re‐initialization equation are presented. A numerical simulation of a premixed turbulent flame is compared to experimental data. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
87.
Transported probability density function modeling of a bluff body stabilized turbulent flame 总被引:2,自引:0,他引:2
A transported probability density function (PDF) approach closed at the joint scalar level is used to model the bluff body stabilized turbulent diffusion flame (HM1) investigated experimentally by Masri and co-workers (Re = 15,800). The current effort extends previous work through the introduction of comprehensive thermochemistry computed via a systematically reduced C/H/N/O mechanism featuring 300 reactions, 20 solved, and 28 steady-state species. Molecular mixing is modelled using the modified Curl’s model. The current computations have been performed via a hybrid Monte Carlo/Finite Volume algorithm. The joint scalar PDF equations are solved using moving particles in a Lagrangian framework, and the velocity field is closed at the second moment level. The redistribution terms are modelled using the Generalized Langevin Model of Haworth and Pope. The principal aim was to investigate the thermochemical effects, and thus a steady-state calculation procedure is adopted. The computations are shown to reproduce experimental mean and rms values of velocities, temperature, mixture, and species mass fractions. In particular, mass fractions of CO and NO are well predicted. Conditional PDFs are also well reproduced although uncertainties in boundary conditions influence results close to the bluff body. 相似文献
88.
C. Olbricht F. Hahn A. Sadiki J. Janicka 《International Journal of Heat and Fluid Flow》2007,28(6):1215-1226
This contribution introduces a hybrid LES-Monte-Carlo method for a coupled solution of the flow and the multi-dimensional scalar joint pdf in two complex mixing devices. For this purpose an Eulerian Monte-Carlo method is used. First, a complex mixing device (jet-in-crossflow, JIC) is presented in which the stochastic convergence and the coherency between the scalar field solution obtained via finite-volume methods and that from the stochastic solution of the pdf for the hybrid method are evaluated. Results are compared to experimental data. Secondly, an extensive investigation of the micromixing on the basis of assumed shape and transported SGS-pdfs in a configuration with practical relevance is carried out. This consists of a mixing chamber with two opposite rows of jets penetrating a crossflow (multi-jet-in-crossflow, MJIC). Some numerical results are compared to available experimental data and to RANS based results. It turns out that the hybrid LES-Monte-Carlo method could achieve a detailed analysis of the mixing at the subgrid level. 相似文献
89.
湍流扩散燃烧的数值研究-PDF方法和火焰面模型的性能比较 总被引:1,自引:0,他引:1
采用标量概率密度函数(PDF)方法、稳态和非稳态火焰面模型三种方法对一个值班湍流CH_4/O_2/N_2射流扩散火焰(Sandia Flame D)进行数值计算,以比较不同燃烧模型的性能。PDF方法通过计算反应标量的PDF输运方程来得到标量分布,而火焰面模型只求解单标量混合物分数的PDF方程,组分和温度分布通过火焰面方程的求解或者火焰面数据库的插值得到。计算结果和实验数据对比表明PDF方法计算结果最好但计算量相当大,稳态火焰面模型则反之。综合而言,非稳态火焰面模型的预测结果相对稳态模型有了非常大的改进,而计算量仍然容易接受,非常适合工程应用。 相似文献
90.
郭萍 《淮阴师范学院学报(自然科学版)》2011,10(4):357-360
CAJViewer作为一款专门的学术文献浏览软件,兼容多种文献格式,具有浏览页面、查找文字、文本识别、邮件传输等功能。支持PDF的浏览和集成OCR文本识别是该软件的两大亮点,准确及时解决可能出现的问题,灵活使用其功能,可极大地方便用户对学术文献的浏览和使用。 相似文献