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Interaction of strong converging shock wave with SF6gas bubble

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Science China(Physics,Mechanics & Astronomy) 2018年第6期61卷 75-83页

作者： Yu Liang zhigang zhai XiSheng Luo Department of Modern Mechanics University of Science and Technology of China

Interaction of a strong converging shock wave with an SF6 gas bubble is studied, focusing on the effects of shock intensity and shock shape on interface evolution. Experimentally, the converging shock wave is generated by shock dynamics theory and the gas bubble is created by soap film technique. The post-shock flow field is captured by a schlieren photography combined with a high-speed video camera. Besides, a three-dimensional program is adopted to provide more details of flow field. After the strong converging shock wave impact, a wide and pronged outward jet, which differs from that in planar shock or weak converging shock condition, is derived from the downstream interface pole. This specific phenomenon is considered to be closely associated with shock intensity and shock curvature. Disturbed by the gas bubble, the converging shocks approaching the convergence center have polygonal shapes, and the relationship between shock intensity and shock radius verifies the applicability of polygonal converging shock theory. Subsequently, the motion of upstream point is discussed, and a modified nonlinear theory considering rarefaction wave and high amplitude effects is proposed. In addition, the effects of shock shape on interface morphology and interface scales are elucidated. These results indicate that the shape as well as shock strength plays an important role in interface evolution.

关键词：相互作用弱收敛冲击波 SF6 水泡煤气动力学理论技术创造

Effect of Atwood number on convergent Richtmyer-Meshkov instability

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Acta Mechanica Sinica 2021年第3期37卷 434-446,I0002页

作者： Jinggang Tang Fu Zhang Xisheng Luo zhigang zhai Department of Modem Mechanics University of Science and Technology of ChinaHefei 230026China Beijing Institute of Space Long March Vehicle Beijing 100076China

Developments of two-dimensional single-mode light/heavy interfaces driven by convergent shock waves are numerically investigated,focusing on the effect of the Atwood number on the Rayleigh-Taylor stabilization,the compressibility and the nonlinearity.Five different test gases,including C〇2,Kr,R22,R12 and SF6,are considered with air as the ambient gas.It is clarified for the first time that the unperturbed interface begins to decelerate when the shock focuses at the convergence center,and the acceleration during the deceleration phase is proportional to the Atwood number.During the first reshock,the interface moves outwards with a deceleration until it starts moving inwards.When the initial interface is weakly disturbed,a more obvious amplitude reduction is observed for the case with a larger Atwood number before the reshock,which means that the Rayleigh-Taylor stabilization is stronger.To assess the effect of the Atwood number on the compressibility and the nonlinearity,three models,including a linear incompressible model,a nonlinear incompressible model and a linear compressible model,are adopted to predict the amplitude growth before the reshock.The results show that the nonlinearity is weak,and is almost not influenced by the Atwood number before the reshock.The compressibility,however,greatly changes the amplitude growth.As the Atwood number increases,the compressibility plays a less significant role in the amplitude growth because a heavier gas is harder to be compressed.Although a gas with a larger specific heat ratio is also difficult to be compressed,the specific heat ratio plays a minor role to the compressibility relative to the Atwood number.During the reshock,the amplitude grows linearly until the nonlinearity in the cases with large Atwood numbers is strong enough to reduce the amplitude growth rate.

关键词： Atwood number Convergent shock wave Richtmyer-Meshkov instability Rayleigh-Taylor effect Compressibility

Mode coupling in converging Richtmyer-Meshkov instability of dual-mode interface

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Acta Mechanica Sinica 2020年第2期36卷 356-366页

作者： Zhangbo Zhou Juchun Ding zhigang zhai Wan Cheng Xisheng Luo Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei 230026China Mechanical Engineering Physical Science and Engineering DivisionKing Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia

The converging Richtmyer-Meshkov(RM)instability on single-and dual-mode N2/SF6 interfaces is studied by an upwind conservation element and solution element solver.An unperturbed case is first considered,and it is found that the shocked interface undergoes a long-term deceleration after a period of uniform motion.The evolution of single-mode interface at the early stage exhibits an evident nonlinearity,which can be reasonably predicted by the nonlinear model of Wang et al.(Phys Plasmas 22:082702,2015).During the deceleration stage,the perturbation amplitude drops quickly and even becomes a negative(phase inversion)before the reshock due to the Rayleigh-Taylor(RT)stabilization.After the reshock,the interface experiences a phase inversion again or does not,depending on the reshock time.The growth of the second-order harmonic in the deceleration stage clearly reveals the competition between the RT effect and the nonlinearity.For dual-mode interfaces,the growth of the first mode(wavenumber k1)relies heavily on the second mode(wavenumber k2)due to the mode coupling effect.Specifically,for cases where k2 is an even or odd multiple of k1,the growth of the first mode is inhibited or promoted depending on its initial amplitude sign and the phase difference between two basic waves,while for cases where k2 is a non-integer multiple of k1,the second mode has negligible influence on the first mode.Through a systematic study,signs of perturbation amplitudes of the generated k2−k1 and k2+k1 waves are obtained for all possible dual-mode configurations,which are reasonably predicted by a modified Haan model(Phys Fluids B 3:2349-2355,1991).

关键词： Converging Richtmyer-Meshkov instability Dual-mode interface Mode coupling

rTMS联合头眼感觉运动整合训练在脑卒中偏瘫患者康复治疗中的应用

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国际医药卫生导报 2024年第2期30卷 234-238页

作者：翟志刚德州市立医院神经内科德州253012

目的探讨重复经颅磁刺激(rTMS)联合头眼感觉运动整合训练在脑卒中偏瘫康复治疗中的应用。方法采用前瞻性研究方法,纳入2020年2月至2023年2月德州市立医院收治的102例脑卒中偏瘫患者作为研究对象,采用摸球法分组,奇数为对照组(51例)、偶... 详细信息

目的探讨重复经颅磁刺激(rTMS)联合头眼感觉运动整合训练在脑卒中偏瘫康复治疗中的应用。方法采用前瞻性研究方法,纳入2020年2月至2023年2月德州市立医院收治的102例脑卒中偏瘫患者作为研究对象,采用摸球法分组,奇数为对照组(51例)、偶数为观察组(51例)。对照组男26例、女25例,年龄(65.23±7.14)岁,进行常规康复治疗;观察组男25例、女26例,年龄(64.89±7.31)岁,在对照组基础上给予rTMS联合头眼感觉运动整合训练,连续治疗6周。治疗前后采用蒙特利尔认知评估量表(MoCA)、简化Fugl-Meyer运动功能评定量表(FMA)、改良Barthel指数(MBI)及简易精神状态评价量表(MMSE)对两组患者进行评估,比较两组患者临床疗效、康复效果满意度。采用t检验、χ^(2)检验进行统计分析。结果观察组临床治疗总有效率为92.15%(47/51),高于对照组的76.47%(39/51),差异有统计学意义(χ^(2)=4.744,P=0.029)。治疗2个月后,观察组MoCA评分、FMA评分、MBI评分、MMSE评分均高于对照组[(26.84±5.32)分比(21.34±4.51)分、(62.38±14.86)分比(53.81±13.27)分、(69.24±21.07)分比(56.75±16.53)分、(28.47±2.01)分比(25.06±1.94)分],差异均有统计学意义(t=5.631、3.072、3.331、8.717,均P<0.05)。观察组康复效果总满意度为90.19%(46/51),高于对照组的72.55%(37/51),差异有统计学意义(χ^(2)=5.239,P=0.022)。结论rTMS联合头眼感觉运动整合训练在脑卒中偏瘫康复治疗中具有显著的临床疗效和康复效果,改善认知功能、运动功能和日常生活能力,具有推广价值。

关键词：重复经颅磁刺激感觉运动整合训练脑卒中偏瘫运动功能康复治疗

Numerical study on Rayleigh-Taylor effect on cylindrically converging Richtmyer-Meshkov instability

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Science China(Physics,Mechanics & Astronomy) 2019年第12期62卷 68-77页

作者： zhigang zhai Fu Zhang ZhangBo Zhou JuChun Ding Chih-Yung Wen Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026China Beijing Institute of Space Long March Vehicle Beijing 100076China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China

Evolution of a two-dimensional air/SF6 single-mode interface is numerically investigated by an upwind CE/SE method under a cylindrically converging circumstance. The Rayleigh-Taylor effect caused by the flow deceleration on the phase inversion(RTPI)is highlighted. The RTPI was firstly observed in our previous experiment, but the related mechanism remains unclear. By isolating the three-dimensional effect, it is found here that the initial amplitude(a0), the azimuthal mode number(k0) and the re-shocking moment are the three major parameters which determine the RTPI occurrence. In the variable space of(k0, a0), a critical a0 for the RTPI occurrence is solved for each k0, and there exists a threshold value of k0 below which the RTPI will not occur no matter what a0 is. There exists a special k0 corresponding to the largest critical a0, and the reduction rule of critical a0 with k0 can be well described by an exponential decay function. The results show that the occurrence of the RTPI requires a small a0 which should be less than a critical value, a large k0 which should exceed a threshold, and a right impinging moment of the re-shock which should be later than the RTPI occurrence. Finally, the effects of the incident shock strength, the density ratio and the initial position of the interface on the threshold value of k0 and on the maximum critical a0 are examined. These new findings would facilitate the understanding of the converging Richtmyer-Meshkov instability and would be helpful for designing an optimal structure of the inertia confinement fusion capsule.

关键词： converging shock wave Rayleigh-Taylor effect Richtmyer-Meshkov instability

The Richtmyer–Meshkov instability of a 'V' shaped air/helium interface subjected to a weak shock

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Theoretical & Applied Mechanics Letters 2016年第5期6卷 226-229页

作者： zhigang zhai Xisheng Luo Ping Dong Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of China

The Richtmyer-Meshkov instability ofa ‘V＇ shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a ‘V＇ shaped interface with accurate initial conditions. Five kinds of ‘V＇ shaped interfaces with different vertex angles are formed to highlight the effects of initial conditions on the flow characteristics. The results show that a spike is generated after the shock impact, and grows constantly with time. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of interface width after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. The linear growth rate of interface width is, for the first time in a heavy/light interface configuration, found to be a non-monotonous function of the initial perturbation amplitude-wavelength ratio.

关键词： Richtmyer-Meshkov instability V shaped interface High-speed schlieren photography

PbGIF1 promoting cell-proliferation in pear fruit is transcriptionally activated by Pb RR1

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Horticultural Plant Journal 2024年第3期10卷 689-697页

作者： Huibin Wang Guangya Sha Rui Gao Jianwen Pang Rui zhai Chengquan Yang zhigang Wang Lingfei Xu College of Horticulture Northwest A&F UniversityYanglingShaanxi 712100China College of Life Science Hebei Agricultural UniversityBaodingHebei 071000China

As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear.According to transcriptome data,we identified PbGIF1was highly expressed during fruit development in cytokinins induced parthenocarpy pear.In the present study,the biofunction of PbGIF1 was initially verified.Overexpression of PbGIF1 promoted fruit size of transgenic tomato.The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing Pb GIF1.The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli.The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets.To investigate the underlying mechanism,the cytokinins-responded factor,PbRR1,was further focused on.The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1.The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays.Taken together,the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.

关键词： PbGIF1 Cell proliferation Pear Fruit development Cytokinins PbRR1

Effect of Bath pH on the Squareness of Electroless CoNiWP Magnetic Films

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Journal of Materials Science & Technology 2008年第5期24卷 712-714页

作者： Haibin CHENG Shuai XU Wenyu ZHAO Suling ZHAO Pengcheng zhai zhigang SUNand Qingjie ZHANGt Pengcheng zhai zhigang SUN Qingjie ZHANG State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

Electroless CoNiWP magnetic films were prepared by varying the bath pH and then characterized by energy dispersive X-ray analysis, X-ray diffraction and magnetic force microscopy, it has been found that the microstructure and the magnetic properties of films were influenced greatly by the bath pH. At the bath pH 8.06, the grain size and coercivity of the films reach maximuml while the squareness （Mr/Ms） of MH curves reaches minimum. The Henkel plots indicates that the exchange-coupling interaction is very weak at this pH, which may be caused by phase-separation and large grain size, and then results in the lowest squareness. At pH above 8.5, obvious exchange-coupling interaction is observed because of the inexistence of phase-separation and the refinement of grain size.

关键词： CoNiWP magnetic film Bath pH Squareness Exchange-coupling interaction

Energy convergence effect and jet phenomenon of shock-heavy spherical bubble interaction

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Science China(Physics,Mechanics & Astronomy) 2015年第12期58卷 180-186页

作者： ZOU LiYong zhai zhigang LIU JinHong WANG YanPing LIU CangLi Laboratory for Shock Wave and Detonation Physics Institute of Fluid Physics China Academy of Engineering Physics Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences University of Cambridge Advanced Propulsion Laboratory Department of Modern Mechanics University of Science and Technology of China

We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock focusing. The multi-fluid Eulerian equation is solved by a finite volume method based on MUSCL-Hancock approach. Based on the numerical schlieren and the distributions of density and pressure, it is found that there are three typical jet structures(outward jet, no jet, inward jet) for different combinations of gas mixture inside the bubble which determine the position of shock focusing relative to the downstream pole of the heavy bubble(upstream of the pole, at the pole, downstream the pole). Compared with the inward jet, the velocity of outward jet is obviously larger. As At increases, the moment of jet formation is postponed, and the maximal values and magnifications of pressure and density increase distinctly. Therefore, the energy convergence effects are heavily enhanced with the increase of bubble gas density.

关键词：射流形成气泡密度相互作用能量会聚激波聚焦压力分布密度分布