单晶铜中冲击波阵面结构的数值模拟研究

 用分子动力学方法模拟计算了在初始温度为0 K时单晶铜中的冲击波结构，相互作用势采用铜的嵌入原子势（EAM），模拟计算结果表明即使是在初始温度为0 K的FCC晶体中，冲击波波阵面后的区域也会向平衡态演化。局域分析表明冲击波阵面后区域的压力、粒子速度、应变和温度随时间逐步变化到稳定态，在所研究的冲击波强度（约262 GPa）下，波后区域的平均压力、粒子速度、应变均在约1 ps内逐渐上升并达到稳定值。动能温度在波阵面处始终为最大值，随着冲击波的传播，波后非零温度区域逐渐扩大，不同时刻的粒子速度分布函数说明波后区域逐渐向热力学平衡态演化，并最终达到热力学平衡，进一步的分析说明局域平衡是系统向平衡态演化的基本过程。     

玻色-爱因斯坦凝聚体中的淬火孤子与冲击波

系统性地探讨了通过淬火相互作用在初态包含暗孤子的玻色-爱因斯坦凝聚体中产生量子冲击波的可能性及其内禀机制.在淬火至无相互作用极限下,解析得到了初始静止孤子的后续动力学,发现了冲击波的存在,并通过量子相干效应加以解释.在淬火至有限相互作用下,通过数值求解Gross-Piatevskii方程也发现了冲击波现象,并且分析了不同情形:往弱相互作用侧淬火时得到的冲击波与无相互作用情形类似;往强相互作用侧淬火时得到的冲击波伴随着孤子的劈裂,且两者存在同步变化关系.进一步探究了冲击波的特性,包括其振幅、速度,并得到了其随淬火相互作用强度变化的全景图谱.这一工作为实验上实现和观测冲击波提供了理论指导.     

水下爆炸强冲击波与平板结构相互作用的理论分析方法

针对水下爆炸一维强冲击波与平板结构的瞬态流固问题开展研究,综合考虑流体和结构材料的可压缩性,引入状态方程建立强冲击波在板表面反射后的波阵面参数关系,得到板表面的反射系数。然后依据动量守恒定律建立平板的运动方程,求解得到板表面的壁压及板的速度时程,形成了水下爆炸强冲击波与平板结构相互作用的理论分析方法。在此基础上给出了强冲击波与平板相互作用的冲量传递比近似估算公式。最后开展平板结构的近距及接触水下爆炸实验,并结合数值计算对理论方法进行验证。结果表明,建立的理论方法与实验及数值模拟结果吻合良好,为水下近距爆炸强冲击波与结构的相互作用分析提供了理论基础。     

计及原子畸变效应后惰性气体原子间相互作用势的计算

用Drude模型和Born-Mayer势系统地研究了原子畸变效应对原子间相互作用的贡献。用Born-Mayer势描述了原子间由于相互重迭而引起的畸变效应,克服了GK-Drude方法的这一缺陷,提出了确定Born-Mayer势参数简单实用的方法。计算结果表明:Born Mayer势能相当准确地反映原子间由于相互重迭而引起的畸变效应;原子畸变效应对原子间的相互作用有重要的贡献。我们求得的惰性气体原子间的相互作用势,不仅改进了用GK-Drude方法求得的结果,而且与实验值符合得很好。     

17F和18Ne与质子的弹性散射角分布

采用逆运动学方法对放射性核束¹⁷F和¹⁸Ne与质子进行弹性散射实验,得到了实验测量微分截面.用较准确描述放射性核素性质的CH89参数化的光学势为初始光学势,用扭曲波玻恩近似的理论计算程序DWUCK4和自动参数搜索程序ABOD对实验数据进行光学势参数理论拟合,得到了与实验数据相符合的光学势参数.将得到的光学势参数进行分析,得到了17F和18Ne实势相互作用均方根半径分别为3.239fm和3.317fm.     

He-NO碰撞体系分波截面的理论计算

首先用Huxley势函数拟合在RCCSD(T)/aug-cc-pVTZ bf理论水平下计算的He-NO相互作用能数据,从而得到了He原子与NO分子相互作用各向异性势;然后用密耦近似方法计算了He-NO碰撞体系的总分波截面、弹性分波截面和非弹性分波截面,并总结了分波截面的变化规律.计算结果表明,拟合势较好地描述了He-NO系统相互作用的各向异性特征,利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题,对进一步研究原子与分子碰撞机理有一定参考价值.     

He-NO碰撞体系微分截面的理论计算

首先用Huxley势函数形式拟合了在RCCSD(T)/aug-cc-pVTZ+bf理论水平下计算的He-NO相互作用能数据，获得了He原子与NO分子相互作用的各向异性势，然后采用密耦近似方法计算了He-NO碰撞体系的总微分截面、弹性微分截面和非弹性微分截面，并总结了微分散射截面的变化规律. 结果表明，拟合势不但表达形式简洁，而且较好地描述了He-NO系统相互作用的各向异性特征；利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题，对进一步研究原子与分子碰撞机理有一定参考价值. 关键词： 各向异性势 势能参数 密耦近似 微分截面     

环形运动势搅拌下偶极玻色-爱因斯坦凝聚体中的von Kármán涡街

数值研究了偶极玻色-爱因斯坦凝聚体(Bose-Einstein condensate, BEC)在环形运动高斯势搅拌时的动力学行为.当高斯势运动速度和尺寸逐渐变化时,偶极BEC中将出现稳定层流、涡旋偶极子、Bénard–von Kármán(BvK)涡街以及混乱激发4种模式.结果表明高斯势在偶极BEC中圆周运动时产生涡街的条件非常苛刻,只有适当尺寸的高斯势以合适的速度运动时,尾流中周期性脱落的具有相同旋量的涡旋对稳定的分布在内外两个圆环上,形成BvK涡街.在实验参数下进行系统数值计算得到了不同偶极相互作用时的相图,讨论了偶极相互作用以及高斯势速度和尺寸对不同激发模式的影响.通过高斯势所受拖拽力的计算,分析了不同激发的物理学机制.     

He-HCl体系各向异性势及分波散射截面的理论研究

首先用BFW势函数形式拟合了在CCSD(T)/aug-cc-pVQZ理论水平下计算的He-HCl相互作用能数据，获得了He原子与HCl分子相互作用的各向异性势；然后采用CC近似方法计算了He-HCl碰撞体系的微分散射截面和分波散射截面，并总结了分波散射截面的变化规律.结果表明，拟合势不但表达形式简洁，而且较好地描述了He-HCl系统相互作用的各向异性特征；利用碰撞体系分子间势的量子化学从头计算结果，可解决势能参数难以确定的问题.对进一步研究原子与分子碰撞机理有一定参考价值. 关键词： 各向异性势 势能参数 密耦近似 分波散射截面     

相互作用势对模拟计算单壁碳纳米管物理吸附储氢的影响

采用巨正则Monte Carlo方法模拟氢分子在单壁碳纳米管中的储存与分布,重点研究了Lennard-Jones势、Crowell-Brown势和Silvera- Goldman势对模拟计算单壁碳纳米管物理吸附储氢的影响.计算结果显示,碳纳米管与氢分子间的相互作用宜采用Lennard-Jones势描述;氢分子与氢分子间相互作用的描述则与碳纳米管的管径有关,管径较小时选Lennard-Jones势较佳,管径偏大时取七参数Silvera-Goldman 势更为合理,而三参数Silvera-Goldman势则不宜采用;并给出了相应的理论解释.     

Interaction of shock waves with a jet wake during gas injection into supersonic stream

In the present paper, we report the results of an experimental study of the interaction region of a planar compression shock produced by a wedge in stream with the wake formed behind a cocurrent gas jet (H₂, air, or Ar) injected into the flow. Depending on the gas jet parameters, three modes of interaction could be distinguished: a strong interaction, observed when the flow velocity in the wake was subsonic; a moderate interaction, observed when a subsonic flow region, bounded by a shock of almost conical shape, formed in the vicinity of the compression shock; and a neutral interaction. Three-dimensional non-stationary Euler equations were solved to numerically examine the interaction of an axisymmetric jet with an oblique shock wave. The obtained interaction regimes were found to be in a reasonable agreement with experimental data.     

Asymmetric interaction of blast waves and shock waves with a body flying at supersonic velocity

The problems of asymmetric interaction of a blunt wedge traveling at supersonic velocity with a cylindrical blast wave from a point explosion and with a plane shock wave are investigated by numerical simulation. The evolution of the interaction flow is analyzed, and data are obtained on how the structure of the shock layer changes. Zh. Tekh. Fiz. 69, 15–19 (May 1999)     

Nanodomain shock wave in near-field laser–material interaction

In this work, molecular dynamics simulation is conducted to explore the shock wave phenomena in a nanodomain in near-field laser–material interaction. A large system consisting of over 800,000 atoms is studied. The work focuses on the kinetic and physical properties of the disturbed gas compression driven by the high speed movement of the molten particulates ejected from the solid target in a nanodomain. The quick interaction between solid and gas atoms compresses the gas and forms a steep shock wave front, which moves at a supersonic speed. The fast compression of gas also induces a steep interface of density, temperature and pressure distribution, which is viewed as typical characteristics of nanoscale shock waves. Evolutions of shock wave front position, velocity and Mach number are also explored and show quick decay during wave propagation.     

爆炸平面冲击波在金属颗粒介质中的衰减

 分析了颗粒介质在冲击载荷下的加载、卸载本构关系,应用特征线理论对平面一维爆炸冲击波在颗粒介质中的衰减进行了计算。结果表明：组成颗粒的材料、孔隙率及炸药的爆速决定了初始冲击波峰值的大小。炸药爆速越高,介质孔隙率越大,材料本身的冲击阻抗越大,初始压力越高。炸药长度、材料本身的冲击阻抗及介质的孔隙率决定了冲击波的衰减速度。炸药长度越小,材料本身的冲击阻抗越大,介质的孔隙率越高,冲击波衰减越快。     

Change in the Space Potential in Glow Discharge Plasma during the Motion of the Shock Wave

Technical Physics - It has been established in experiments on the interaction of a shock wave with a glow discharge that the motion of the shock wave is accompanied by an increase in the potential...     

Shock wave-inertial microbubble interaction: a theoretical study based on the Gilmore formulation for bubble dynamics

The Gilmore formulation for bubble dynamics coupled with zeroth-order gas diffusion were used to investigate theoretically the cavitation activity produced by a modified XL-1 lithotripter [J. Acoust. Soc. Am. 105, 1997-2009 (1999)]. The model calculation confirms many of the basic features in bubble dynamics observed experimentally, in particular the strong secondary shock wave emission generated by in situ lithotripter shock wave-inertial microbubble interaction. In addition, shock wave-inertial microbubble interaction produced by a Dornier HM-3, the most commonly used clinical lithotripter, was evaluated. It was shown that the forced collapse of inertial microbubbles with strong secondary shock wave emission could be produced consistently, provided that an appropriate preceding shock wave and interpulse delay were used. Further, it was demonstrated that truncation of the tensile stress of the lithotripter shock wave could significantly reduce the large expansion of the bubble following shock wave-inertial microbubble interaction, which may alleviate the risk for vascular injury during shock wave exposure.     

Dynamics evolution of shock waves in laser–material interaction

In this work, the dynamics and internal structure of shock waves in picosecond laser–material interaction are explored at the atomistic level. The pressure of the shock wave, its propagation, and interaction zone thickness between the plume and ambience are evaluated to study the effect of the laser absorption depth, ambient pressure, and laser fluence. Sound agreement is observed between the MD simulation and theoretical prediction of shock wave propagation and mass velocity. Due to the strong constraint from the compressed ambient gas, it is observed that the ablated plume could stop moving forward and mix with the ambient gas, or move backward to the target surface, leading to surface redeposition. Under smaller laser absorption depth, lower ambient pressure, or higher laser fluence, the shock wave will propagate faster and have a thicker interaction zone between the target and ambient gas.     

药柱冲击波在有机玻璃中的衰减特性研究

用作图法得到了药柱与有机玻璃隔板界面处的冲击波压力,利用AUTODYN 6.1软件模拟了药柱冲击波在有机玻璃隔板中的衰减过程,并用锰铜压力计法测量了药柱冲击波在不同厚度有机玻璃隔板中的压力,并根据理论公式计算了有机玻璃中相应的冲击波速度、波后质点速度和密度。结果表明,理论计算结果、数值模拟结果与试验测量结果一致,并根据试验结果得到了冲击波压力在有机玻璃中的衰减规律;AUTODYN 6.1软件能够准确地预测冲击波在有机玻璃隔板中的衰减特性。     

Non-invasive determination of shock wave pressure generated by optical breakdown

Shock waves generated by a laser-induced plasma were investigated using a pump-and-probe technique. Both 7-ns and 40-ps laser pulses at 1.06 m were employed to initiate breakdown in water. Two He-Ne laser beams were used as a velocity probe, allowing the accurate measurement of the shock velocity around the plasma. The maximum shock pressure was determined from the measured shock velocities, the jump condition and the equation of state for water. The conservation of the total momentum of the shock front was used to derive expressions for the shock velocity, particle velocity and shock pressure vs. the distance (r) from the center of the plasma. For a shock wave of spherical symmetry, the shock pressure is proportional to 1/r ². Our work shows that the expanding plasma initially induces a shock wave; the shock wave dissipates rapidly becoming an acoustic wave within 300–500 m.