pdf两相流模型有限研究网格混合算法及数值模拟

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'pdf两相流模型有限研究网格混合算法及数值模拟'
两相湍流PDF模型研究中,颗粒速度-坐标空间中的PDF输运方程的求解一直以来都 是一个难题,本课题组曾依据颗粒PDF方程和轨道方程的对等性,用速度空间局部PDF 方程的解析解联合Monte Carlo方法求解,提岀了高维空间中PDF输运方程的“有限分 析/颗!狈椒。木文提出一个求解高维空间PDF方程的新方法一一“有限分析/网格(FAG)”方法。 根据两相流动屮的颗粒运动过程是一种具有时■空非线性的色噪声系统的随机运动过 程,可以提取湍流指数关联特征,建立色噪声扩维方法的两相流PDF输运方程。继而 通过高斯积分得到颗粒相的连续方程和动量方程,建立没有封闭的场模型。再从PDF 的定义出发,通过对任何量的概率密度积分得到该量的平均值,通过积分法来构造颗粒 的任意阶矩,继而得到方程的统计平均拉氏方程组。由场模型和统计平均拉氏方程组共 同组成封闭的模型。构造差分格式用数值方法对模型求解,通过计算得到颗粒在流场中 的分布,获得完整的“有限分/析网格(FAG)”求解方法。对经典两相流动壁面射流进行数值模拟,对比分析了模拟值和实验值,同时也与“有 限分析/颗粒(FA/MC)”进行了结果对比分析。从比较结果发现“有限分析/网格(FAG) 方法”能够更为准确的预报颗粒平均速度,脉动速度及颗粒浓度等在流场中的分布;新 方法计算结果曲线更为光滑,同时也对颗粒脉动速度的计算结果有了改善。结果表明“有 限分析/网格(FAG)方法”求解颗粒PDF方程是可行有效的。关键词:数值模拟,两相流,PDF模型,湍流,有限分析/颗粒方法,有限分析/网格方 法ABSTRACTIn the study of the particle PDF transport equation of two-phase flows, it is always a difficult problem about how to solve the particle transport equation in high-dimensional velocity-coordinate space. On the basis of the equivalence of the PDF equation and the particle trajectory equation, the finite Analytic/Particle approach as numerical method was put forward in our previous work. In the finite Analytic/Particle approach method, we combined together the analytical solution of velocity space local-PDF equation with Monte Carlo method.In this paper, a new method to solve high-dimensional PDF equation, named —Finite Analysis/Gridll approach is promoted. Considering the motion of the particle in two phases flow has the nature of space-time nonlinear, the random particles motion is regarded as a colored noise system. By extracting the correlation features of turbulence, we established a two-phase flow PDF transport equation with noise expanding dimension method. In the second step, through using Gauss integral skill we got the particulate phase continuity equation and momentum equation and finished the unclosed Eulian model of two-phase flow. From the definition of PDF, we can use the probability integral easily to get the average value of any amount equations. Under this premise construct the particles order moment equations and got the statistical average equations finally. The new closed two-phase flow model is made up of the unclosed Eulian model and the moment equations. Using numerical method we can solved the two-phase model and we call the closed model and its solve method as —Finite Analysis/Gridll method.A wall-jet-flow loaded with solid particles is simulated both using the Finite Analytic/Grid (FAG) method and the Finite Analytic/Particle (FA/MC) method, and the numerical results were all been analyzed. Compared with the experimental results it is show that the Finite Analytic/Grid (FAG) method is much better to forecast the average velocity of particles than the Finite Analytic/Particle (FA/MC) method. The Finite Analytic/Grid (FAG) method can improve the calculation precision of particle fluctuating velocity. At the same time the calculation of particles concentration equation becomes easily, more smoothly curve of particles concentration distribution wa
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pdf 两相 模型 有限 研究 网格 混合 算法 数值 模拟
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