共查询到12条相似文献,搜索用时 62 毫秒
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利用从细长体理论出发得到的三维分段积分法和湍流简化方法模拟了大量纤维粒子在圆管湍流内的运动.统计了不同Re数下计算区域内的纤维的取向分布,计算结果与实验结果基本吻合,结果表明湍流的脉动速度导致纤维取向趋于无序,且随着Re数的增加,纤维取向的分布越来越趋于均匀.其后又考虑了纤维速度和角速度的脉动,二者都充分体现了流体速度脉动的影响,且纤维速度的脉动在流向上的强度大于横向,而其角速度的脉动在流向上的强度小于横向.最后统计了纤维在管道截面上的位置分布,说明Re数的增加加速了纤维在管道截面上的位置扩散. 相似文献
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底部加热的肥皂泡是一种全新的二维热对流模型,在实验中已发现肥皂泡上的岛涡运动规律与飓风轨迹规律一致.然而,肥皂泡的曲面特征对其准二维流场的数值模拟以及数据分析造成了较多困难.针对肥皂泡球面几何特征,该文介绍了其直接数值模拟(DNS)方法,及其流场空间波数谱、湍流通量和结构函数的计算分析方法.开展了Ra=3×10^(7),3×10^(9),3×10^(11)的数值计算,并获得了相应的波数谱、通量和湍流结构函数.计算结果表明,肥皂泡上速度的小尺度脉动特征满足Bo59的理论标度律,通过湍动能与拟涡能通量特征,发现在该准二维湍流场中存在湍流能量双级串现象.且随着Rayleigh数的增加,大尺度结构湍能量减小,更小尺度湍流结构能量增加. 相似文献
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从运动方程和本构方程出发,推导得到了含柱状粒子两相流场的修正Orr-Sommerfeld方程,然后在边界层流场中,采用数值计算方法,得到了含柱状粒子流场的稳定性中性曲线,给出了流场失稳的临界雷诺数.结果表明在所述情况下,柱状粒子对流场起着抑制失稳的作用,而且抑制的程度随着柱状粒子体积分数和长径比的增加而提高. 相似文献
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Flügge's equations of motion for cylindrical shells are used to analyze the generation of travelling waves in a tube of an ultrasonic travelling wave transport system. The vibration-shape of a semi-infinite acrylic tube with structural damping excited by a piezoelectric ring at the end is calculated and the influence of the driving frequency is shown. Starting with an exponential ansatz the frequency dependent wavenumbers can be determined. Three frequency bands with different combinations of imaginary, real and complex wavenumbers can be found. Supposing a semi-infinite tube with given boundary conditions at the end of excitation the vibrations of the tube can be calculated depending on the frequency. Simulation agrees well with experimental results. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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E. Marušic-Paloka 《Applied Mathematics and Optimization》2001,44(3):245-272
We consider an injection of incompressible viscous fluid in a curved pipe with a smooth central curve γ . The one-dimensional model is obtained via singular perturbation of the Navier—Stokes system as ɛ , the ratio between the cross-section area and the length of the pipe, tends to zero. An asymptotic expansion of the flow
in powers of ɛ is computed. The first term in the expansion depends only on the tangential injection along the central curve γ of the pipe and the velocity as well as the pressure drop are in the tangential direction. The second term contains the
effects of the curvature (flexion) of γ in the direction of the tangent while the effects of torsion appear in the direction of the normal and the binormal to γ . The boundary layers at the ends of the pipe are studied. The error estimate is proved.
Accepted 21 March 2001. Online publication 9 August 2001. 相似文献
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Louis N. Howard 《Studies in Applied Mathematics》1990,83(4):273-285
Under certain conditions, high-Rayleigh-number convection in a horizontal layer exhibits an organized pattern of large-scale flow superposed on an irregular structure of turbulent plumes. Bounds on the heat and momentum fluxes in such a flow, which provide upper estimates of the possible level of the large-scale flow, are presented. 相似文献