共查询到20条相似文献,搜索用时 641 毫秒
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深入研究库仑碰撞,对两种库仑碰撞模型-Ta模型与Nanbu模型在理论上进行了对比分析,详细阐述了两种模型中散射角大小的区别.在已有的采用Ta模型的全三维粒子模拟/蒙特长罗(PIC/MCC)算法基础上,采用Nanbu模型对电子间库仑碰撞计算模块重新进行了算法设计.分别应用Ta模型、Nanbu模型和无库仑碰撞的全三维PIC/MCC算法对国外热门负氢离子源JAEA 10A中的电子能量沉积进行了模拟分析.模拟结果与实验结果的对比分析发现:1)库仑碰撞使电子能量分布更接近于麦克斯韦分布;2)相对于传统的Ta模型,Nanbu模型的散射角考虑了多体碰撞的累加效果从而具有更高的期望值,按其模拟得到的电子温度具有更高的精度.这些为国内外学者设计相关算法指明了方向. 相似文献
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三体碰撞在一定条件下可简化为两体碰撞处理,本文计算三体碰撞问题的几种简化模型与数值实验结果的偏差,讨论了简化模型的适用条件。 相似文献
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运用一种改进光滑粒子动力学(SPH)方法模拟了相溶和不相溶两种情况下的等直径微液滴碰撞动力学过程. 为提高传统SPH方法的数值精度和稳定性, 采用一种不涉及核导数计算的核梯度改进形式; 为处理液滴界面张力采用修正的van der Waals表面张力模型. 通过模拟牛顿液滴碰撞聚并变形过程并与相关文献或试验结果进行对比, 验证了改进SPH 方法模拟微液滴碰撞过程的可靠性. 随后, 研究了基于van der Waals模型相溶聚合物微液滴碰撞聚并变形过程及不相溶微液滴碰撞后的反弹、分离过程, 讨论了碰撞过程中碰撞速度、碰撞角度、密度比等参数对碰撞变形过程的影响, 分析了流体桥、旋转角度等因素的变化情况.
关键词:
光滑粒子动力学
微液滴
聚合物液滴
碰撞 相似文献
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转动传能的量子干涉效应在静态池实验中发现,并且已测得积分干涉角.为了得到更多关于传能的准确信息,应利用分子束进行实验.本文基于一阶含时波恩近似,模拟了利用分子束实验进行量子干涉效应研究的理论模型.此模型采用了Lennard-Jones相互作用势和直线轨道近似.通过本文建立的模型,研究了影响干涉效应的微分干涉角的因素,并且得到了徽分干涉角和碰撞速度、碰撞参数及碰撞体的关系.此理论模型对于指导分子束实验具有重要的意义. 相似文献
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由于碰撞壁面后液滴内部流动的复杂性, 以及气-液-固三相间的相互作用, 对液滴碰撞壁面形态变化的数学理论研究有较大的难度, 因此所见者多为实验和数值模拟. 本文通过对液滴受力状态的分析, 得到了惯性力、黏性力和表面张力带经验系数的表达式, 并进一步建立了液滴碰撞壁面振荡模型, 得到了液滴铺展半径的振荡表达式, 以及表面张力、黏性系数等参数对液滴铺展的影响. 最后通过与液滴衰减振荡数值模拟结果的对比, 确定了液滴振荡模型中的修正系数, 验证了模型的可行性.
关键词:
液滴碰撞
振荡
铺展半径/高度
数值模拟 相似文献
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双流体颗粒-壁面碰撞模型用于旋流流动 总被引:1,自引:0,他引:1
对旋流两相流动,用考虑壁面粗糙度的双流体颗粒-壁面碰撞模型,结合二阶矩两相湍流模型和不同颗粒相边界条件,进行了数值模拟。结果表明,由于考虑了各方向雷诺应力之间的相互转化,雷诺应力从平均运动中得到能量,以及壁面对颗粒运动的衰减作用等因素,该颗粒壁面碰撞模型给出的模拟结果与实验符合较好,而广泛应用的零梯度颗粒壁面边界条件给出的模拟结果最差。 相似文献
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Effects of the mid-air collision on sand saltation 总被引:1,自引:1,他引:1
As to the fact that the effects of saltating particles’ mid-air collision on the sand transport rate are often neglected in
the current theoretical models describing sand saltation movement, expressions to calculate velocity diversity of saltating
particles after mid-air collision are presented through collision theory of hard ball in this paper. Then, the theoretical
model of the wind blown sand movement at the steady state, taking account of coupled interaction between saltation particles
and wind, is combined with the model of the mid-air collision probability to calculate the saltating particles’ mass flux
at heights, the sand transport rate, and further, their changing rules. The comparison of the results with those when the
mid-air collision is not considered suggests that the mass flux at heights and the sand transport rate in this paper are less,
and much closer, respectively, to the corresponding experimental values. The difference between the sand mass fluxes without
and with consideration of mid-air collision increases at first, and then decreases as the height increases, exhibiting the
stratified characteristics.
Supported by the Key Project of National Natural Science Foundation of China (Grant No. 10532040), the National Natural Science
Foundation of China (Grant Nos. 40571018 and 10772073), the New Century Outstanding Talent of the Ministry of Education of
China, and the Science Fund of the Ministry of Education of China for PhD Program (Grant No. 20060730014) 相似文献
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The combustion characteristics of freely falling droplets, individually generated by the merging of colliding methanol and alkane droplets, were investigated and compared with those for pure methanol and alkanes. The merging of the nominally immiscible methanol and alkanes was manifested in an apparently adhesive, but unmixed, manner in all test conditions. An air bubble was found to be trapped at the colliding interfaces where they were “adhered,” with the trapping favored for head-on or near head-on collision orientations. The trapped air bubble ostensibly induced heterogeneous nucleation of the methanol, being facilitated by the relatively low limit of superheat of methanol. Consequently, the droplet exploded almost immediately upon ignition, leading to an extremely short overall lifetime. For collision orientations that were more off-centered, bubble trapping and thereby heterogeneous nucleation were not favored. However, delayed, albeit strong, microexplosion occurred through homogeneous nucleation of methanol at the contacting interface. The global burning rate was therefore again augmented. In general, microexplosion was facilitated for high-boiling-point alkanes such as hexadecane and tetradecane. The co-vaporization of methanol and alkane from their respective hemispherical segments constituting the adhered droplet also led to flame colors that were more bluish than yellowish, indicating the reduction of soot from alkane burning in the presence of methanol vapor. In light of the difficulty of forming stable methanol/oil emulsions, the potential of separate injection of oil and methanol in opposed jet arrangement, in direct-injection engines to facilitate collision, is suggested. 相似文献
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以不连续运行模式下的电流反馈型Buck-Boost变换器为例,导出了一类具有三段形式的分段光滑迭代映射方程,数值仿真得到了输入电压变化时的分岔图.结果表明,发生分岔时映射雅可比矩阵的特征值以不连续的方式跳跃出复平面上的单位圆,而且映射总有某个或某些轨道点位于相平面中不同区域的边界上,即映射随输入电压的变化会发生边界碰撞分岔现象,如由周期态到周期态以及由周期态到混沌态的分岔.
关键词:
分段光滑系统
边界碰撞分岔
混沌 相似文献
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Continuous droplet rebound on heated surfaces and its effects on heat transfer property: A lattice Boltzmann study 下载免费PDF全文
《中国物理 B》2021,(4)
A thermal multiphase lattice Boltzmann(LB) model is used to study the behavior of droplet impact on hot surface and the relevant heat transfer properties.After validating the correctness of the codes through the D~2 law,the simulations of intrinsic contact angle and the temperature-dependent surface tension are performed.The LB model is then used to simulate the droplet impact on smooth and micro-hole heated surface.On the smooth surface,the impinging droplet is reluctant to rebound,unless the intrinsic wettability of the solid surface is fairly good.On the micro-hole surface,however,the micro-holes provide favorable sites for generating a high-pressure vapor cushion underneath the impinging droplet,which thereby facilitates the continuous droplet rebound.For the continuously rebounding droplet.The time evolution of volume and temperature display obvious oscillations.The achievable height of the rebounding droplet increases as the intrinsic wettability of the solid surface becomes better,and the maximum transient heat flux is found to be directly proportional to the droplet rebounding height.Within a certain time interval,the continuous rebounding behavior of the droplet is favorable for enhancing the total heat quantity/heat transfer efficiency,and the influence of intrinsic wettability on the total heat during droplet impingement is greater than that of the superheat.The LB simulations not only present different states of droplets on hot surfaces,but also guide the design of the micro-hole surface with desirable heat transfer properties. 相似文献
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研制了多功能球-球碰撞实验仪,利用该仪器对三组碰撞实验的研究发现,未退火小球和未退火小球碰撞可近似为弹性碰撞,其恢复系数为0.96;未退火小球和退火小球、退火小球和退火小球之间的碰撞为非弹性碰撞。本实验源自生活中的打靶实验,将其进行改造升级为物理实验中的研究性设计性实验,在启发学生创新思维和培养学生发散思考方面具有显著作用。 相似文献
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Complementary to the conventional experimental studies on N* from πN and γ(*)N reactions, the e+e-, pp and pp collisions can give novel insights into these N* resonances. While the e+e- collisions through production and decay of vector charmonium ψ provide a nice isospin filter for a simultaneously study of N*, △*, ∧*, ∑* and 2*, the pp collisions should be the best place for producing those △*++ with large coupling to p+p though pp →nA*++ reaction, and the pp collisions should be the best place for looking for those N* with large coupling to σN. 相似文献
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小球与均质自由杆的碰撞 总被引:2,自引:2,他引:0
讨论了小球与自由杆碰撞过程中所遵从的物理规律,明确了完全非弹性碰撞过程的能量特征,指出完全非弹性碰撞后两物体不一定粘在一起共同运动的事实. 相似文献