簇间可分的鲁棒模糊C均值聚类算法

与经典的K均值聚类算法相比,模糊C均值(FCM)聚类算法通过引入模糊因子,考虑不同聚类数据簇之间的相互关系,得到可分性更好的聚类结果。但是模糊因子的引入,使得任意一个样本点都存在模糊性...国家自然科学基金(61203176);; 福建省自然科学基金(2013J05098,2016J01756)~

风沙两相流中近沙床颗粒应力分析

通过统一的计算流体力学(CFD)与颗粒离散元(DEM)相结合的方法对典型风沙流场中近沙床的颗粒运动进行了二维数值模拟。气相湍流采用了K-E模型，颗粒的碰撞采用了软球模型。对计算结果的统计发现，颗粒的碰撞仅存在于沙床上方7mm以下，但是4$\sim$7mm为过渡层，颗粒穿越过渡层发生的碰撞是随机的。颗粒雷诺应力存在于沙床上方250mm以下，随着高度的增加，颗粒雷诺应力急剧下降。在沙床高度250mm以上，只有气相剪切应力起作用。这时，颗粒的浓度非常低，虽然颗粒和气相之间仍然有速度差，但是由此产生的单位体积曳力很低，因而不会对气相剪切应力造成影响

三维风沙运动的CFD-DEM数值模拟

采用计算流体力学(Computational Fluid Dynamics,CFD)和颗粒离散元(Discrete Element Method,DEM)耦合的方法模拟三维风沙运动,并且将三维模拟结果和二维模拟结果以及实验结果进行了对比.计算结果表明:沙粒水平速度随着高度按幂函数规律增加,沙床表面附近沙粒撞击和起跳速度的概率分布均可用对数正态函数描述,沙粒撞击和起跳角度的概率分布均可用指数函数描述,沙粒水平速度,展向速度和垂直速度在不同高度处的概率分布可分别用对数正态分布,正态分布和正态分布表示.与二维计算结果的分析对比表明:二维计算得到的颗粒速度的分布规律和三维计算结果类似,但二维计算的颗粒表观密度明显偏大,由此导致输沙量计算偏大.和实验结果的对比表明:三维计算得到的颗粒速度概率分布与实验基本保持一

余热锅炉增设放散烟道后的传热数值计算

利用余热锅炉回收废气余热是企业节能的重要一环。但在对余热锅炉进行检修的时候废气却仍然持续进入锅炉,这给余热锅炉的检修带来了困难。设置放散烟道可以阻隔废气持续进入锅炉,同时也有助于锅炉自身热气的排放。利用计算流体力学的方法对余热锅炉增设放散烟道后的传热进行了数值模拟。结果表明,在总烟管道设置放散烟道同时配合在锅炉底部增加鼓风机的方法能有效降低锅炉内部的温度,提高了锅炉检修的效率,保障了检修人员的安全

求解运动方程的一种不等时间步长的显式数值积分方法

在波动有限元模拟中, 若采用传统的显式数值积分方法求解运动方程, 计算时间步长需采用计算区内满足稳定条件要求的最小时间步长. 然而, 对于大部分计算区域, 这一时间步长过小, 是不必要的. 本文提出了一种不等时间步长的显式数值积分方法, 其基本思想是不同的计算区域采用满足各自稳定条件的计算时间步长. 最后, 本文通过数值试验检验了这一方法的可行性及其对数值计算精度的影响

A varying time-step explicit numerical integration algorithm for solving motion equation

If a traditional explicit numerical integration algorithm is used to solve motion equation in the finite element simu- lation of wave motion, the time-step used by numerical integration is the smallest time-step restricted by the stabil- ity criterion in computational region. However, the excessivel..

CFD-DEM simulation of three-dimensional aeolian sand movement

A three-dimensional CFD-DEM model is proposed to investigate the aeolian sand movement. The results show that the mean particle horizontal velocity can be expressed by a power function of heights. The probability distribution of the impact and lift-off velocities of particles can be described by a log-normal function, and that of the impact and lift-off angles can be expressed by an exponential function. The probability distribution of particle horizontal velocity at different heights can be described as a lognormal function, while the probability distribution of longitudinal and vertical velocity can be described as a normal function. The comparison with previous two-dimensional calculations shows that the variations of mean particle horizontal velocity along the heights in two-dimensional and three-dimensional models are similar. However, the mean particle density of the two-dimensional model is larger than that in reality, which will result in the overestimation of sand transportation rate in the two-dimensional calculation. The study also shows that the predicted probability distributions of particle velocities are in good agreement with the experimental results

Rayleigh波入射情形下的断层效应

本文运用数值模拟方法对Rayleigh波入射情形下的断层效应进行分析,结果表明:断层对Rayleigh面波具有隔震作用,随断层深度的增加其隔震效果更加明显,且水平向的隔震效果强于竖向.在入射波一侧,由于断层的作用使接触带附近的反应增强,随着断层破碎带宽度的增加,竖向反应变化特征明显不同于水平向反应变化特征

Sand storms: CFD analysis of Reynolds stress and collision stress of particles near sand bed

Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand storms, the causes and the manners of particle motions must be studied in detail. In this paper a standard k-epsilon model is used for the gas phase simulation and the discrete element method (DEM) is used to predict the movements of particles using an in-house procedure. The data are summarized in an Eulerian-Eulerian regime after simulation to get the statistical particle Reynolds stress and particle collision stress. The results show that for the current case the Reynolds stress and the air shear stress predominate in the region 20-250 mm above the initial sand bed surface. However, in the region below 3 mm, the collision stress must be taken into account in predicting particle movement. (C) 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved