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胡涛,李祥龙,关思,何丽华
《中国工程科学》 2014年 第16卷 第11期 页码 36-41
基于大型非线性动力分析软件LS-DYNA，选用弹塑性模型*MAT_PLASTIC_KINEMATIC 和JWL方程，建立无限岩体介质中中深孔爆破时连续装药结构和分段装药结构三维模型，并进行了数值模拟，再现了两种装药结构爆破过程中的应力发展过程，对比分析了它们在Von Mises 有效应力分布、自由面有效应力峰值、孔壁压力分布及加速度等衰减上的差异。结合工程现场爆破实践验证了分段装药结构可以明显改善爆破效果。
关键词： 中深孔台阶爆破 分段装药结构 ANSYS/LS-DYNA 数值模拟
通过一个等价雷诺数揭示层流到湍流的转捩区域 Article
陈晓东
《工程（英文）》 2019年 第5卷 第3期 页码 576-579 doi: 10.1016/j.eng.2018.09.013
Flow transition from laminar to turbulent mode (and vice versa)—that is, the initiation of turbulence—is one of the most important research subjects in the history of engineering. Even for pipe flow, predicting the onset of turbulence requires sophisticated instrumentation and/or direct numerical simulation, based on observing the instantaneous flow structure formation and evolution. In this work, a local Reynolds number equivalence γ (ratio of local inertia effect to viscous effect) is seen to conform to the Universal Law of the Wall, where γ = 1 represents a quantitative balance between the abovementioned two effects. This coincides with the wall layer thickness (y+ = 1, where y+ is the dimensionless distance from the wall surface defined in the Universal Law of the Wall). It is found that the characteristic of how the local derivative of γ against the local velocity changes with increasing velocity determines the onset of turbulence. For pipe flow, γ ≈ 25, and for plate flow, γ ≈ 151.5. These findings suggest that a certain combination of γ and velocity (nonlinearity) can qualify the source of turbulence (i.e., generate turbulent energy). Similarly, a re-evaluation of the previous findings reveals that only the geometrically narrow domain can act locally as the source of turbulence, with the rest of the flow field largely being left for transporting and dissipating. This understanding will have an impact on the future large-scale modeling of turbulence.
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