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非均匀交错网格上的Temam方法及驱动方腔流动的数值模拟 总被引:3,自引:0,他引:3
给出一种有效求解多重尺度问题的计算方法,把作者在交错网格上的修正Temam格式[5]推广到非均匀交错网格,网格分布是根据边界层厚度由无奇异连续坐标变换来实现,以保证计算精度,连续方程约束用压力修正投影法来实现.所导致的非均匀网格上的Poisson方程用FISHPACK中的广义循环约减法程序求解。对驱动方腔流动进行了数值模拟,给出了Re数为100,400,1000,5000的定常结果.这些结果定量上与文献中的结果一致,在Re数较大时分辨出三级涡,但计算效率有显著提高。 相似文献
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基于浸没边界-格子Boltzmann方法,对方形截面微通道内椭球颗粒的惯性迁移与旋转动力学行为进行数值研究,发现微通道内椭球颗粒的惯性迁移存在两种主要的运动状态:①翻转状态,即椭球颗粒前进过程中长轴始终在中心对称平面内;②滚动状态,即椭球颗粒前进过程中长轴始终垂直于中心对称平面.研究表明:在低Re数(Re=10)下颗粒以两种状态随流体迁移至平衡位置;在较大Re数(50≤Re≤200)下最终均以翻转状态随流体迁移,随Re数增加,平衡位置先逼近壁面后远离壁面.通过对不同运动状态下椭球颗粒周围的微观流场进行分析,提示该微观流动在颗粒惯性聚焦行为特征中有重要影响,并从流体和颗粒的惯性角度对颗粒不同运动状态的转换机理给出解释. 相似文献
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文[1]完满地解决了给定模M下乘同余序列(MCS)达最大周期δ(M)的充要条件问题。本文将[1]的结果进一步推广,得到MCS序列具有周期m(≤δ(M))的充要条件。文后给出例子,说明本文所给结果的正确性。 相似文献
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通过结合格子Boltzmann方法(LBM)和虚拟区域(Fictitiou sDomain)思想,建立格子Boltzmann-虚拟区域(LB-DF/FD)方法.采用两套网格系统,欧拉网格用于流体,拉格朗日网格用于固体.原有的LBM在计算运动固体的受力方面存在数据振荡,LB-DF/FD方法改进了此缺陷.为验证该方法,模拟圆柱绕流、圆形颗粒在无限长通道中平动及在无限大流场中转动三种情况,结果与其他数值解及理论解符合得很好.利用该方法模拟低雷诺数下通道中串列旋转圆柱周围的流场,分析圆柱间距(g)及雷诺数(Re)对流场结构的影响.给出Re=0.001,0.1和10下,0.2≤g≤8.0的流线结构、圆柱升力、阻力以及力矩等数值结果.结果表明,g对流场的结构及圆柱的受力有显著影响,Re对圆柱阻力及Stokes单元数目的影响较大. 相似文献
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要根据[1]中给出的MCS序列xn≡αxn-1(modM)具有周期m的充要条件,确定其相应全部参数α,可归结为模M之m阶单位根的计数与确定问题,而此问题对一般复合模M至今未见解决。本文解决了这个问题,从而也解决了MCS序列具有周期m的全部参数α的计数和确定问题。 相似文献
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MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究 下载免费PDF全文
研究MC与Mn+1ACn(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构Mn+1ACn稳定性的内在原因和设计新型Mn+1ACn结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与Mn+1ACn 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成Mn+1ACn. 与M2PC和M2SC 相比, M2AlC和M2SiC可以更为容易地被分离成二维 M2C结构.
关键词:
MAX相结构
第一性原理
电子结构
过渡金属碳化物 相似文献
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Plane Couette flow of viscoelastic fluids is shown to exhibit a purely elastic subcritical instability at a very small-Reynolds number in spite of being linearly stable. The mechanism of this instability is proposed and the nonlinear stability analysis of plane Couette flow of the Upper-Convected Maxwell fluid is presented. Above a critical Weissenberg number, a small finite-size perturbation is sufficient to create a secondary flow, and the threshold value for the amplitude of the perturbation decreases as the Weissenberg number increases. The results suggest a scenario for weakly turbulent viscoelastic flow which is similar to the one for Newtonian fluids as a function of Reynolds number. 相似文献
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V. M. Molochnikov N. I. Mikheev A. A. Paereliy K. R. Khairnasov 《Thermophysics and Aeromechanics》2008,15(4):573-582
Visualization data and results of combined measurements of flow quantities in flow with separation past a rib at nominally
laminar regime of channel flow are reported. In the separation region, the flow is found to be essentially three-dimensional
and unsteady, exhibiting a distinct cellular structure and flow zones with transverse motion. It is shown that the rib-induced
flow separation gives rise to low-frequency fluctuations of flow velocity and initiates the turbulence transition in the channel
flow. The critical Reynolds number at which flow instability starts developing in the channel is estimated. It is shown that
at Reynolds numbers higher than the critical Reynolds number the linear integral scale of flow velocity fluctuations in the
channel is defined by the duct size. 相似文献
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微细光滑管内气体的流动与传热特性研究 总被引:5,自引:0,他引:5
在评述当前微细管内流动和换热特性研究的基础上提出了需考虑流体压缩性对速度剖面的影响。可压缩流动守恒方程组的数值解结果表明:运动流体的压缩性不仅使管内平均流速增加,而且使速度剖面更加饱满,从而使局域阻力系数和换热系数增加。与此同时,尽管管道的长细比很大,亦不可能出现充分发展的速度和温度剖面。这是由于微细管道中由于阻力引起的压力降可以很大,它所引起的流动加速达较大马赫数时,压缩性对阻力系数和传热系数的影响就不能忽略。 相似文献
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This work investigates the effect of entropy generation rate within the flow of two immiscible micropolar fluids in a horizontal channel bounded by two porous beds at the bottom and top. The flow is considered in four zones. Zone IV contains the flow of viscous fluid in the large porous bed at the bottom, zone I and zone II contain the free flow of two immiscible micropolar fluids, and zone III contains the flow of viscous fluid in the thin porous bed at the top. The flow is assumed to be governed by Eringen’s micropolar fluid flow equations in the free channel. Darcy’s law and Brinkman’s model are used for flow in porous zones, namely, zone IV and zone III, respectively. The closed form expressions for entropy generation number and Bejan number are derived in dimensionless formby using the expressions of velocity, microrotation and temperature. The effect of physical parameters like a couple stress parameter and micropolarity parameter on velocity, microrotation, temperature, entropy generation number and Bejan number are investigated. 相似文献
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Computational fluid dynamics is extensively used in the design methodology of medical devices. However, for such applications,
the predictive capabilities of CFD codes are highly dependent upon geometry, which most of the time is extremely complex,
and flow conditions. The study concerns a ventricular assist device (VAD) where the exit flow, generated through a diffuser,
is of particular importance for blood damage predictions. The difficulty to predict the flow lies in the fact that the Reynolds
number range includes the transition Reynolds number of the separated diffuser flow as well as the critical Reynolds number
of pipe flows. In order to choose the appropriate CFD methodology in terms of flow hypothesis and turbulence model, an experimental
setup of the diffuser was built to run PIV velocity measurements and to analyze the flow pattern with the influence of Reynolds
number. The flow is described with mean and variance values of the in-plane velocity components and timeresolved results are
used to visualize the development of unsteady phenomena introduced in the diffuser separated region. An optimal filter is
also used to remove noise in measured velocity vector fields. 相似文献