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1.
We propose a 4-velocity unidimensional discrete Boltzmann model with two different speeds 2, 1 and two different masses 1, 2. With the three conservation laws of mass, momentum, and energy satisfied, we can introduce a nontrivial temperature. First, we determine the similarity shock waves satisfying physical properties: positivity, shock stability, inequalities of the subsonic and supersonic flows, increase or decrease of both mass and temperature across the shock. It results that either the speed of the shock front is higher than the speed 1 of the slow particles and the shocks are compressive or less than 1 and the shocks are rarefactive. We observe overshoots of the temperature, across the shock, with bumps higher and higher as the shock front speed increases. Second, we study the (1+1)-dimensional shock waves. They represent the superposition and collision of two compressive shocks traveling in opposite directions and we observe temperature overshoots for not too large times.  相似文献   
2.
To find a model that describes the gas diffusion on irradiated polymers (Makrofol KG polycarbonate) the diffusion constants have been measured with argon as diffusion gas. The polymers were irradiated with uranium, gold and lead ions of about 10 MeV/u and ion fluences between 1×1010 and 4×1011 ions/cm2. The ion irradiated probes show two quite different dependencies of the diffusion constant on the ion energy loss. These effects are strongly related to the fluence of the irradiation. In case of low ion fluences, the diffusion constant is up to 8 times higher than that of pristine material. In the probes with high ion fluences we observe a decrease of diffusion constant to half the value of the pristine material. To understand the dependence of the diffusion constant on ion fluences we apply a model of compacting. This model describes the compacting ability of shockwaves arising from latent tracks. A track formation model is suggested. When an ion penetrates the foil it creates shockwaves around its path. These shockwaves put compacting forces on earlier created latent tracks in the same foil.  相似文献   
3.
The structure and evolution of the laser-induced vapor plume and shockwave were measured from femtosecond time resolved shadowgraph images. By changing the wavelength of the probe beam (400 and 800 nm), differences in the opacity of the vapor plume were measured as a function of delay time from the ablation laser pulse. The evolution of the temperature and electron number density during and after the ablation laser pulse were determined and compared for ablation in argon and helium background gases. A laser supported detonation wave (LSD) observed for ablation in argon, blocks the incoming laser energy and generates a high-pressure region above the vapor plume.  相似文献   
4.
The Nd:YAG laser-induced breakdown of 20 μm glass microspheres was investigated using time-resolved optical shadow and Schlieren images. Time-resolved imaging showed the location of the initial breakdown and the shockwave motion over its first 400 μm of expansion. Measured shockwave velocities were in the range of 1–10 km/s and showed a linear dependency on laser fluence within 30 ns.  相似文献   
5.
In this paper, single pulse (SP)- and double pulse (DP)- Laser Induced Breakdown Spectroscopy (LIBS) on metallic titanium, aluminum-based alloy and copper-based alloy have been studied by spectrally resolved imaging to find out the fundamental difference in terms of fluid-dynamic and chemical aspects. To better clarify the different nature of SP- and DP-Laser Induced Plasma (LIP) a qualitative theoretical model including both fluid-dynamics and chemical processes has been applied for the interpretation of the experimental results. Moreover, an attempt to quantify the mechanisms inducing the DP-LIBS enhancement has been made. By the analysis of spectrally resolved imaging data, the temporal and spatial maps of the emission signal and of the corresponding DP-LIBS enhancement have been built in order to improve the analytical information conveyed. Finally, it has been pointed out the important effect of the different environment where SP- and DP-LIPs expand, as well as its relevance to the understanding of the basic questions underlying the comparison between SP- and DP-LIBS.  相似文献   
6.
A new particle saltation removal model in laser-induced plasma shockwave cleaning is presented due to the drawbacks in other particle removal models. Considering the elastic energy stored in the adhered particle during shockwave-particle interaction, the threshold of the particle elastic deformation height, leading to the particle removal, is obtained. With taking the collision between gas molecules in plasma shockwave rear and adhered particle into account, the threshold of the plasma shockwave Mach number is also obtained which is a requirement to the shockwave strength. It is found that the smaller particle needs stronger shockwave than the larger particle. The gas pressure distribution characteristics in the plasma shockwave rear offer a saltation surrounding to the particle, and it is another requirement to the shockwave strength for a successful particle saltation. Finally, particle-cleaning experiment using laser-induced plasma shockwave proves the correctness of the particle saltation model.  相似文献   
7.
双曝光全息干涉法用于风洞中激波流场的研究   总被引:3,自引:0,他引:3  
王建岗  罗景山 《光子学报》1997,26(4):373-378
本文论述了双曝光全息干涉法在激波流场研究中的应用.对于形状不规则模型在超音速风洞中产生的激波流场,由于对这种流场进行数值计算几乎不可能,从实验上对其进行定量测量就显得尤为重要.本文很好地解决了某种不规则模型超音速激波流场的定量测量问题,获得了激波流场的有限条纹全息干涉图,并利用图象处理技术对干涉图进行了细化处理,再用人机交互的方式采集数据计算出条纹的位移量,最后用拉普拉斯变换法计算出流场的密度分布值.  相似文献   
8.
激光驱动冲击波在铝-金阻抗匹配靶中的传播稳定性   总被引:1,自引:2,他引:1       下载免费PDF全文
 针对神光Ⅱ第九路激光条件,利用1维JB程序和多台阶靶技术对冲击波在铝 金阻抗匹配靶中的传播稳定性进行了理论和实验研究,实验结果与理论结果基本吻合。结果表明,激光驱动冲击波在铝 金阻抗匹配靶中传播时,高阻抗待测材料金中的冲击波稳定传播最大距离急剧减小。因此,在进行铝-金阻抗匹配靶物理参数设计时,应保证高阻抗材料金台阶厚度满足冲击波传播稳定性,然后再按照阻抗匹配实验中两种材料的冲击波速度比来确定低阻抗标准材料铝的台阶厚度。根据神光Ⅱ第九路激光条件,铝-金阻抗匹配靶中铝基底厚度选取为30 μm左右较好,金台阶和铝台阶厚度应分别小于10 μm和17 μm。  相似文献   
9.
High-speed holographic interferometry was employed to visualize and record Shockwave phenomena. We performed three kinds of holographic interferometry for visualization and recording of the propagation of a Shockwave: a real-time holographic interferometer with a high-speed framing camera, a real-time holographic interferometer with a high-speed streak camera and a double-pulse laser holographic interferometer with a dual-reference-beam module. The experimental results were compared and their advantages and disadvantages are discussed. The experimental results clearly show the high-speed Shockwave propagation and give the feasibility of quantitative interpretation of high-speed gas-dynamics.  相似文献   
10.
The shockwave propagation and aerosol formation during femtosecond laser ablation (fs-LA) of dielectric materials (Li2B4O7, Y:ZrO2) in ambient air were monitored using shadowgraphy and light scattering. Three independent shockwave fronts were observed originating from (i) the instantaneous compression of ambient gas during the initial stage of fs-LA, (ii) a secondary compression caused by material ejection, and (iii) an air breakdown well above the target surface. In addition, particle size distributions were found to be multimodal implying the co-existence of condensational growth and supplementary particle production pathways such as phase explosion or critical point phase separation (CPPS). As a consequence, fs-LA of Li2B4O7 resulted in the formation of primary aggregates reaching diameters of > 10 μm. In contrast, aggregates formed during fs-LA of Y:ZrO2 covered a size range < 1 μm. Our data, furthermore, indicate the existence of a breakdown channel in the ambient atmosphere being capable to carry plasmatic, i.e. non-condensed matter beyond the primary shockwave barrier which may occasionally causes a spatial separation of material released. Assuming the Taylor-Sedov model of explosion to be valid the over-all energy dissipated in acoustic transients was found to exceed values of 50%.  相似文献   
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