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To date, there are very few studies on the transition beyond second Hopf bifurcation in a lid-driven square cavity, due to the difficulties in theoretical analysis and numerical simulations. In this paper, we study the characteristics of the third Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme rectently developed by us. We numerically identify the critical Reynolds number of the third Hopf bifurcation located in the interval of (13944.7021,13946.5333) by the method of bisection. Through Fourier analysis, it is discovered that the flow becomes chaotic with a characteristic of period-doubling bifurcation when the Reynolds number is beyond the third bifurcation critical interval. Nonlinear time series analysis further ascertains the flow chaotic behaviors via the phase diagram, Kolmogorov entropy and maximal Lyapunov exponent. The phase diagram changes interestingly from a closed curve with self-intersection to an unclosed curve and the attractor eventually becomes strange when the flow becomes chaotic. 相似文献
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采用超高效液相色谱(UPLC)定量测定银莱汤中10种有效成分的含量并用于其质量评价。采用Waters ACQUITY UPLC HSS T3色谱柱(2.1 mm×100 mm,1.8μm),以0.1%甲酸水溶液-0.1%甲酸乙腈为流动相梯度洗脱,3波长切换(0~10 min,320 nm;10~16 min,350 nm;16~30 min,320 nm)测定。结果表明,该方法可在30 min内实现银莱汤中10种有效成分的基线分离,10种成分在各自质量浓度范围内线性关系良好(r≥0.9992),检出限为0.0188~0.0750μg·mL-1,定量下限为0.0625~0.250μg·mL-1。检测得到银莱汤中10种成分的平均含量为0.204~38.129 mg·g-1,其中黄芩苷的含量最高,槲皮苷的含量最低。将该方法用于3批样品分析,所测成分含量稳定、一致性好。该文建立的分析指标相对全面、合理可行,能更好地表征及评价银莱汤质量。 相似文献
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界面曲率对空化的演变及结构载荷的影响 总被引:1,自引:0,他引:1
研究了近体水下爆炸中结构表面外形的变化对空化的形成、演变及结构载荷的影响.为了真实地考虑流体与固体的非线性相互作用,近期发展的流-固耦合多介质Riemann问题技术和修正的虚拟介质方法被推广应用于处理流体与固体的相互作用中.研究发现,凹的表面设计不但可以导致爆炸冲击波局部汇聚和强化,而且随后可以强化空化破裂所造成的冲击,研究进一步发现,这种强化作用还是非线性的,随曲率的增加而非线性增强;相反地,凸的表面设计可以减低爆炸冲击波冲击,而且可以弱化空化的产生,但其影响是非常有限的. 相似文献
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To date, there are very few studies on the second Hopf bifurcation in a driven square cavity, although there are intensive investigations focused on the first Hopf bifurcation in literature, due to the difficulties of theoretical analyses and numerical simulations. In this paper, we study the characteristics of the second Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme recently developed by us. We numerically identify the critical Reynolds number of the second Hopf bifurcation located in the interval of(11093.75, 11094.3604) by bisection. In addition, we find that there are two dominant frequencies in its spectral diagram when the flow is in the status of the second Hopf bifurcation, while only one dominant frequency is identified if the flow is in the first Hopf bifurcation via the Fourier analysis. More interestingly, the flow phase portrait of velocity components is found to make transition from a regular elliptical closed form for the first Hopf bifurcation to a non-elliptical closed form with self-intersection for the second Hopf bifurcation. Such characteristics disclose flow in a quasi-periodic state when the second Hopf bifurcation occurs. 相似文献
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目前,许多高精度差分格式,由于未成功地构造与其精度匹配的稳定的边界格式,不得不采用低精度的边界格式.本文针对对流扩散方程证明了存在一致四阶紧致格式,它的边界点的计算格式和内点的计算格式的截断误差主项保持一致,给出了具体内点和边界格式;并分析了此半离散格式的渐近稳定性.数值结果表明该格式是四阶精度;在对流占优情况下,本文边界格式的数值结果比四阶精度的显式差分格式的的数值结果的数值振荡小,取得了不错的效果,理论结果得到了数值验证;驱动方腔数值结果显示,本文对N-S方程的离散格式具有很好的可靠性,适合对复杂流体流动的数值模拟和研究. 相似文献
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虚拟流体方法为模拟具有清晰物质界面的多介质流动问题提供了一种简便途径.尤其基于多介质Riemann问题解的修正虚拟流体方法及其变体,能够真实考虑到界面附近非线性波的相互作用和物质性质的影响,可以有效解决各种界面强间断等挑战性难题,具有巨大的工程应用潜力.文章重点回顾了虚拟流体方法的发展历史,总结和对比了各种代表性版本在模拟可压缩多介质流时的界面条件定义方式和多维推广方式,并介绍了该方法的设计原则和精度分析方面的研究进展.文章还回顾了该方法在其他更广泛和更具挑战性典型科学问题中的最新应用进展,并对方法的优势和特点进行了总结. 相似文献
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