共查询到19条相似文献,搜索用时 187 毫秒
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采用基于欧拉一拉格朗日的双向耦合模型对三维气固两相平面射流中颗粒与流体的双向耦合作用进行了直接数值模拟.在考虑颗粒相的反作用后,气相运动采用直接耦合求解,计算颗粒场时,选取Stokes数为0.1的较小颗粒,采用Lagrangian方法跟踪其运动.重点考察了颗粒相与流体相之间的相互作用,分析了不同固相载率的颗粒对流场特性以及对自身扩散的影响.模拟结果表明由于颗粒的影响,在射流入口处流场最初生成的两个大涡沿横向被拉伸,而在射流下游区域,涡结构则沿流向被拉伸;在射流的下游,颗粒降低了流场中心区域的流向平均速度,削弱了流场中心区域的湍流强度.此外,跟单向耦合相比,双向耦合情况下的颗粒分布更加均匀,并且均匀程度随固相载率的增加而增大. 相似文献
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气固两相混合层流场双向耦合的数值研究 总被引:5,自引:0,他引:5
采用双向耦合模型对有涡配对的二维气固两相混合展数值模拟,在考虑颗粒对流场反作用基础上进一步对颗粒间通过流体的相互作用进行分析。流场用拟谱方法求解,颗粒用颗粒轨道模型跟踪。结果发现,流场中大涡卷起和配对仍居主导地位;颗粒St数为O(0.1)~O(1)时,颗粒减弱了流场雷诺应力强度,加快涡量扩散; St数为O(1)时,颗粒分布极不均匀,主要集中在渴的边缘. 相似文献
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三维格子涡方法模拟自由下落颗粒群 总被引:1,自引:0,他引:1
本文发展了基于双向耦合的三维格子涡方法,采用涡方法模拟流场中的涡量变化及涡元运动,使用双势法求解速度场,采用拉格朗日方法跟踪颗粒相.利用该模型模拟了颗粒群的自由下落及下落过程引起的气相流动,模拟结果与实验吻合良好。结果显示空气相速度径向分布满足高斯分布,颗粒相流量对颗粒群的扩散影响不显著,而流量增大会引起颗粒速度的增大. 相似文献
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两相混合层中颗粒运动的数值模拟 总被引:6,自引:0,他引:6
本文采用离散涡方法对平板混合层流动进行了数值模拟,得到了与实验完全定量符合的速度场。再用单向耦合方法模拟了混合层流场中颗粒的运动。分析了混合层流动中大尺度涡结构及Stokes数对颗粒扩散的影响。与前人工作中所采用的每个时间步一个颗粒在固定的位置进入计算域的方法不同,本文中每个时间步有多个颗粒在入口处以随机的横向位置进入计算域。因此,在不需增加太多计算量的基础上,计算域中可以包含足够多的颗粒以获得较精确的统计结果。采用本文方法得到的颗粒速度场与实验结果定量符合得很好。 相似文献
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Ayyalasomayajula S Gylfason A Collins LR Bodenschatz E Warhaft Z 《Physical review letters》2006,97(14):144507
We describe Lagrangian measurements of water droplets in grid generated wind tunnel turbulence at a Taylor Reynolds number of R(lambda)=250 and an average Stokes number (St) of approximately 0.1. The inertial particles are tracked by a high speed camera moving along the side of the tunnel at the mean flow speed. The standardized acceleration probability density functions of the particles have spread exponential tails that are narrower than those of a fluid particles (St approximately 0) and there is a decrease in the acceleration variance with increasing Stokes number. A simple vortex model shows that the inertial particles selectively sample the fluid field and are less likely to experience regions of the fluid undergoing the largest accelerations. Recent direct numerical simulations compare favorably with these first measurements of Lagrangian statistics of inertial particles in highly turbulent flows. 相似文献
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气固两相流动的数值计算 总被引:5,自引:0,他引:5
1前言两相流系统的研究主要有三种方法:宏观的连续介质理论(欧拉法)[1]、微观的运动理论、粒子运动的拉格朗日方法.和单相流动的主要差别在于,两相流动模拟要考虑两相间的相互作用,即耦合作用.如果载荷比较低,粒子的存在并不影响气流的速度场,但气流决定着粒子的轨道和参数的变化,这种情况叫单向耦合(one-waycoupling).在早期的数值分析模型中,单相耦合假定常被人们采用。但当载荷比较高时,不但要考虑气相对粒子的影响,还要考虑粒子的存在对气流的影响,即双向耦合作用(two-waycoupling)[2].这种两相间复杂的相互作用… 相似文献
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通过理论推导提出了一种评价高速流动PIV示踪粒子随流能力的松弛特性分析模型,在法向Mach数大于1.4时具有良好的适用性.将新模型应用于试验测量,发展了高速流动PIV系统和示踪粒子布撒技术,验证了高速流动PIV的定量化测量能力.针对空间发展的二维超声速气固两相混合层,数值模拟了不同Stokes数和对流Mach数(Mc)下的粒子跟随性以及弥散和迁徙运动,结果表明:相同对流Mach数,粒径越小的示踪粒子跟随性越好,Stokes数在[1, 10]范围内的粒子有最大扩散距离.示踪粒子的直径大小决定其在超声速混合层大涡拟序结构中的分布特征,且粒径越小,气体与粒子的掺混越剧烈.相同粒径的粒子,对流Mach数越大跟随性越差. 相似文献
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Alexandre Dupuis Philippe Chatelain Petros Koumoutsakos 《Journal of computational physics》2008,227(9):4486-4498
We present a lattice-Boltzmann method coupled with an immersed boundary technique for the simulation of bluff body flows. The lattice-Boltzmann method for the modeling of the Navier–Stokes equations, is enhanced by a forcing term to account for the no-slip boundary condition on a non-grid conforming boundary. We investigate two alternatives of coupling the boundary forcing term with the grid nodes, namely the direct and the interpolated forcing techniques. The present LB–IB methods are validated in simulations of the incompressible flow past an impulsively started cylinder at low and moderate Reynolds numbers. We present diagnostics such as the near wall vorticity field and the drag coefficient and comparisons with previous computational and experimental works and assess the advantages and drawbacks of the two techniques. 相似文献
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Particle modulation to turbulence is investigated experimentally by means of PDPA, PIV and flow visualization for a gas-particle
two-phase jet flow. Large particles can enhance the small-scale vortex, so that gas-phase turbulence intensity is increased,
while small particles may delay the rolling up of the gas vortex, so that gas-phase turbulence intensity is attenuated. The
critical particle size range for such different effects is between 150 σm and 200 σm, corresponding to the Stokes number is
between 88 and 157 under the present flow conditions. The PIV results show small particles can retain the gas-phase vortex
structure, while large particles can break large vortex structure. The particle Stokes number is not the only judgment standard
whether particles enhance or attenuate gas-phase turbulence. The CTI (Change of Turbulence Intensity) number can mark off
particle modulation on turbulence in two-phase flow, but more studies are needed. 相似文献