Mechanism of Zhongtiao Aulacogen Related to Breakup of Columbia Supercontinent

The mechanism of the breakup of supercontinent is a scientific frontier in the field of supercontinent study.The rifting and breakup of supercontinent has long been considered to be related to mantle plume.Paleo-

Transformation of single drop breakup from binary to ternary and multiple in turbulent jet flows

By releasing liquid drops in turbulent jet flows,we investigated the transformation of single drop breakup from binary to ternary and multiple.Silicone oil and deionized water were the dispersed phase and continuous phase,respectively.The probability of binary,ternary,and multiple breakup of oil drops in jet flows is a function of the jet Reynolds number.To address the underlying mechanisms of this transformation of drop breakup,we performed two-dimensional particle image velocimetry(PIV)experiments of single-phase jet flows.With the combination of drop breakup phenomenon and two-dimensional PIV results in a single-phase flow field,these transformation conditions can be estimated:the capillary number ranges from 0.17 to 0.27,and the Weber number ranges from 55 to 111.

Mechanics of Mafic Dyke Swarms and Breakup of Supercontinent

Dyke swarms can be divided into three types:parallel dyke swarms,radiating dyke swarms and fan-shape dyke swarm,for which the mechanisms of formation are different(Fig.1).Parallel dyke swarms form in response

Breakup Structure of Two-phase Jets with Various Momentum Flux from a Porous Injector

Spray structure and atomization characteristics were investigated through a comparison of a porous and a shear coaxial injector. The porous injector shows better atomization performance than the shear coaxial injector. To in- crease atomization performance and mixing efficiency of two-phase jets, a coaxial porous injector which can be applicable to liquid rocket combustors was designed and tested. The characteristics of atomization and spray from a porous and a shear coaxial injector were characterized by the momentum flux ratio. The breakup mechanism of the porous injector is governed by Taylor-Culick flow and axial shear forces. Momentum of injected gas flow through a porous material which is composed of sintered metal is radically transferred to the center of the liquid column, and then liquid column is effectively broken up. Although the shapes of spray from porous and shear co- axial jets were similar for various momentum ratio, spray structures such as spray angle and droplet sizes were different. As increasing the momentum flux ratio, SMD from the porous injector showed smaller value than the shear coaxial injector

Relative probabilities of breakup channels in reactions of^(6.7)Li with^(209)Biat energies around and above the Coulomb barrier

Coincidence measurements of breakup fragments in reactions of^(6.7)with^(209)Bi at energies around and above the Coulomb barrier were carried out using a large solid-angle covered detector array.Through the Q values along with the relative energies of the breakup fragments,different breakup components(prompt breakups and delayed breakups)and different breakup modes(α+t,α+d,α+p,andα+α)are distinguished.A new breakup mode,α+t,is observed in^(6)Li-induced reactions at energies above the Coulomb barrier.Correlations between breakup modes and breakup components as well as their variations with the incident energy are investigated.The results will help us better understand the breakup effects of weakly bound nuclei on the suppression of a complete fusion,particularly for the above-barrier energies.

Numerical simulation of mechanical breakup of river ice-cover

Ice jams and ice dams in rivers will cause significant rises of water levels. Under extreme conditions, the ice flooding during winter or early spring may occur. In this paper, by considering the fluid-solid coupling effect caused by the water and the ice cover, the mechanisms of the mechanical breakup of the river ice cover are studied. A formula is obtained for determining whether or not the mechanical breakup process would happen under the hydraulic pressure of the flow. Combined with the hydraulic model under the ice covered flow, a numerical model is built and the interaction between the discharge, the hydraulic pressure under the ice cover and the date for the mechanical breakup of the river ice cover is simulated. The simulated results of the dates for the mecha- nical breakup of the river ice cover agree very well with the field observations of the breakups of the river ice cover in the Hequ Reach of the Yellow River. Therefore, the numerical model might serve as a good preliminary step in studying the breakup of the river ice-cover, evidencing many important parameters that affect the ice-cover process,

单晶铝中微喷射的分子动力学研究

采用非平衡分子动力学模拟方法,研究了方形冲击波在含有圆锥和正弦缺陷的单晶铝中一维和二维的微射流演化.利用正向和反向粒子追踪技术获得了微射流的粒子源,发现微射流不同部位的粒子源结构与缺陷类型密切相关,微射流的形成是从缺陷表层到内层的分层聚集过程.锥形情况下的射流头部速度最初急剧增加,然后快速下降至恒定速度;锥形和正弦情况下的喷射体积先经历非线性增加,后保持不变.通过进一步对喷射粒子数量、密度、速度和温度之间的关系分析,发现在圆锥和正弦情况下,当冲击速度为6 km/s时喷射物速度在冲击方向上基本呈线性变化,且射流最大速度位于射流头部;但在正弦情况下,当冲击速度为2 km/s时喷射物速度在冲击方向上波动变化,射流头部速度低于为头部后侧的速度.更重要的是,本文揭示了两种机制,即一维射流的颈缩与二维射流的孔洞增长和贯穿,它们主导了射流的破碎.实际上,速度、温度和压力的扰动都有助于射流破碎,其中速度扰动对其破碎具有最重要影响.此外,速度梯度会引起孔洞边界变厚,从而导致射流头部密度增加.