Hydrodynamics of resonance oscillations of columns of inelastic particles

We study oscillations of a one-dimensional (1D) column of N slightly inelastic particles, produced by a piston vibrating at one end of a closed tube. It is found that for large enough vibrational amplitudes of the piston, the column oscillates periodically with the period equal to the vibrational period. The oscillation patterns are governed by the shock waves propagating across the column. The averaged kinetic energy per particle is shown to be proportional to the square of the vibrational frequency, omega. This energy also strongly depends on the vibrational amplitude. The maximal value of this kinetic energy achievable by these external vibrations is found to be of order omega(2)L(2), where L is the total volume (length) of the tube free of particles. The above results on the column resonance oscillations are also predicted by a 3D hydrodynamic model of an inelastic granular gas.     

管内气体声振荡特性的气-动格式模拟

本文对活塞驱动的谐振管中气体的非线性振荡,给出了考虑热、黏作用的气-动格式模型,并数值分析了气体振荡的演化过程和谐振时的激波特性.研究了频率对谐振荡行为、模式及压力波形的影响.并分析了压比随频率的变化关系.计算结果与早期文献研究的实验及计算结果具有好的一致性.模拟结果显示了气-动格式在谐振管内非线性气体振荡模拟中的数值...     

Nonlinear space-charge waves on an intense relativistic electronbeam

The propagation characteristics of the large-amplitude space-charge waves on a modulated intense relativistic electron beam are calculated. The beam is assumed to propagate inside a straight drift tube, and is guided by a strong axial magnetic field. Only the analytical and simulation results of this relatively simple system are given. It is shown that the slow space-charge waves may cease to propagate if the modulating voltage is sufficiently high, whereas the fast waves are relatively unaffected by the nonlinearity. The limiting electron velocity inferred from the analytical theory is in excellent agreement with particle simulation. The implications are discussed     

Double-diaphragm shock tube at the Ioffe Physicotechnical Institute

Results of numerical calculations of the flow in a double-diaphragm shock tube with a tailored contact surface are reported. The calculations were carried out using a model of an ideal shock tube allowing for the real properties of the driver gas at high pressures and equilibrium thermodynamics of the processes behind the shock waves at Mach numbers M _s1 of the shock wave in the working gas varying in the range 5–25. Flow regimes with a tailored contact surface were obtained for Mach numbers M _s1=6.3, 11, and 15 using the double-diaphragm shock tube at the Ioffe Physicotechnical Institute. Under these conditions, the parameters of the working gas were kept constant for more than 1 ms. The calculated data were compared with the experimental results and it was shown that the calculated data may be used to determine the section lengths in a double-diaphragm shock tube and to estimate its operating time. The calculated values of the initial pressure in the sections of the tube were substantially lower than those achieved experimentally. Measurements were made of the static pressure along the axis of a conical nozzle during the expansion of hydrogen (initial temperature T ₀=293 K) and shock-heated nitrogen (T ₀=4000 K). It is found that the expansion of hydrogen is accompanied by deactivation of the rotational degrees of freedom, and that partial freezing of the vibrational degrees of freedom takes place in the nitrogen stream. Zh. Tekh. Fiz. 67, 88–95 (November 1997)     

Pressure dynamics in a supersonic flow during initiation of pulse surface sliding discharges

The supersonic air flow at Mach numbers of 1.1–1.6 in a shock tube is experimentally investigated during initiation of nanosecond pulse surface sliding discharges. The shadow images of the flow field after discharge initiation, which characterize the dynamics of shock waves propagating from the discharge area, are obtained. Periodic pressure pulsations on the shock tube channel wall are recorded. The pressure dynamics is shown to correspond to both the motion of shock waves from the discharge area and a supersonic flow of the discharge-excited gas near the channel wall. The pressure increase on the shock tube channel wall was 6–18%, as compared to the pressure in an unperturbed flow. Original Russian Text ? D.F. Latfullin, I.V. Mursenkova, N.N. Sysoev, 2009, published in Vestnik Moskovskogo Universiteta. Fizika, 2009, No. 3, pp. 114–116.     

Nonlinear electrostatic waves in inhomogeneous dense dusty magnetoplasmas

The nonlinear electrostatic drift waves are studied using quantum hydrodynamic model in dusty quantum magnetoplasmas. The dissipative effects due to collisions between ions and dust particles have also been taken into account. The Korteweg-de Vries Burgers (KdVB) like equation is derived and analytical solution is obtained using tanh method. The limiting cases of KdV type solitary waves, Burger type monotonic shock waves and oscillatory shock solutions are also presented. It is found that both hump and dip type solitary structures are possible in quantum dusty plasmas. However, amplitude and width of the nonlinear structure depend on the dust charge polarity and its concentration in electron-ion quantum plasmas. The monotonic shock like structure is independent of the quantum parameter. It is found that shock strength is increased in the presence of positively charged particles in comparison with negatively charged dust particles. The oscillatory shock structures are also obtained and it is found that change in dust charge polarity only shifts the phase of the oscillatory shock in plasmas. The numerical results are also presented for illustration.     

Computer simulation of the drift of solid particles caused by resonance gas oscillations in the open channel

Computer simulation methods are used to study the drift of solid spherical particles suspended in the open channel due to longitudinal oscillations of the gas column. The gas velocity field consists of periodic nonlinear waves and an acoustic flow. The particles move under the action of the Stokes force. Particle distributions in the wave field of the open channel are obtained in the vicinity of the first, second and third eigen-frequencies of the gas column. The particle’s spatial distribution features attributed to the particle’s drift under the action of acoustic radiation are revealed.     

管束穿孔板的管腔耦合共振吸声机理研究

为了揭示管束穿孔板共振吸声结构的吸声机理,利用热黏性条件下基于有限元算法的管束穿孔板仿真模型,研究了平面声波正入射条件下,管束穿孔板内部声场分布特征,并利用阻抗管对吸声系数的理论仿真结果进行了试验验证.结果表明,管束穿孔板在低频主要靠腔体共振吸声,在高频主要靠管共振吸声,管束穿孔板整体呈现出较为明显的管腔耦合共振吸声特征。管束穿孔板共振时管中声强和质点法向振速较大,高频次吸声峰频点处管中和腔中均有驻波形成,频率越高驻波数量越多.管束穿孔板的耦合共振受到管长、腔深、穿孔率和管内径等参数变化的影响,管长对高频耦合共振的影响最大,管长增大使高频主吸声峰频点移向低频,并使相邻主吸声峰之间的间距减小.      

平面弱激波加载下球形气泡演化的实验研究

 利用高速摄影机直接观测了激波加载下球形气泡的演化过程。采用白色的烟雾颗粒对气泡内透明的测试气体进行染色,直接观察到了气泡界面。通过对平面弱激波加载下轻气体气泡和重气体气泡进行研究,成功验证了轻气体气泡和重气体气泡演化过程中出现的典型界面结构,获得了弱激波加载轻气体气泡中背风涡环的环状几何结构。运用相关方法分析了轻气体气泡实验初期的流场分布,得到的结果与理论分析结果吻合得很好,对于此类实验的数据处理具有一定的启发意义。同时,实验中使用的烟雾颗粒法为今后在球形气泡实验中引入更为精确的平面激光诱导荧光技术（PLIF）、激光粒子图像测速技术（PIV）等实验测试系统提供了布撒示踪粒子的范例。     

Application of PIV to over-expanded supersonic flows: Possibilities and limits

Two-dimensional velocity distributions outside a Mach 2.0 supersonic nozzle have been investigated using a digital particle im age velocimetry (PIV). Mean velocities , vor ticity field and volume dilatation field were obtained from PIV images using 0 .33 μm titanium dioxide (TiO₂) particle. The seeding particle of larger size , 1.4 μrn Ti0₂, was also used for the experimental comparison of velocity lag downstream of shock waves. The results have been compared and analyzed with schlieren photographs for the locations of shock waves and over-expanded shock structure to inspect possibilities and limits of a PIV technique to over-expanded supersonic flows. It is found that although the quantitative velocity measurement using PIV on over-expanded supersonic flows with large velocity and pressure gradients is limited, the locations of normal shock and oblique shock waves can be resolved by the axial/radial velocity fields, and over-expanded shock structure can be predicted by vorticity field and volume dilatation field which are acquired from the spatial differential of the velocity field.     

Self-Similar Solution of Spherical Shock Wave Propagation in a Mixture of a Gas and Small Solid Particles with Increasing Energy under the Influence of Gravitational Field and Monochromatic Radiation

Similarity solution for a spherical shock wave with or without gravitational field in a dusty gas is studied under the action of monochromatic radiation. It is supposed that dusty gas be a mixture of perfect gas and micro solid particles. Equilibrium flow condition is supposed to be maintained and energy is varying which is continuously supplied by inner expanding surface. It is found that similarity solution exists under the constant initial density. The comparison between the solutions obtained in gravitating and non-gravitating medium is done. It is found that the shock strength increases with an increase in gravitational parameter or ratio of the density of solid particles to the initial density of the gas, whereas an increase in the radiation parameter has decaying effect on the shock waves.     

Self-Similar Solution of Spherical Shock Wave Propagation in a Mixture of a Gas and Small Solid Particles with Increasing Energy under the Influence of Gravitational Field and Monochromatic Radiation

Similarity solution for a spherical shock wave with or without gravitational field in a dusty gas is studied under the action of monochromatic radiation. It is supposed that dusty gas be a mixture of perfect gas and micro solid particles. Equilibrium flow condition is supposed to be maintained and energy is varying which is continuously supplied by inner expanding surface. It is found that similarity solution exists under the constant initial density. The comparison between the solutions obtained in gravitating and non-gravitating medium is done. It is found that the shock strength increases with an increase in gravitational parameter or ratio of the density of solid particles to the initial density of the gas, whereas an increase in the radiation parameter has decaying effect on the shock waves.     

Resonances of intensities and oscillation frequencies in ring gas lasers. I

Narrow resonances of the intensities and oscillation frequencies of counterpropagating waves in the vicinity of the center of the quantum transition in a pure-isotope ring gas laser have been studied. It is shown that the origin of resonances is related to the presence of sources causing unequal losses and/or frequencies of the counterpropagating waves in the laser cavity. The resonance change of intensities, which is accompanied by the resonance behavior of the medium dispersion for each of the waves, is not related to resonance changes of the saturated gain coefficients of the nonlinear medium. The resonances are caused by the redistribution of energy between the waves. The character of resonance changes of frequencies and intensities depends on the nature of nonreciprocity present in the cavity.

     

Transient modes of propagation of the shock wave-reaction zone complex in methane-air mixtures

The dynamics of the combustion of stoichiometric methane-air mixtures during the passage from a larger-diameter to a smaller-diameter tube is experimentally studied. The combined effect of increases in the velocity and duration of the gas flow and in the degree of its turbulization due to a decrease in the cross sectional area of the tube and installation in it of turbulizing obstacles considerably enhance the probability of onset of combustion mode with the formation of strong shock waves. Combustion waves led by a shock wave that ignites the mixture at obstacles and propagates at a velocity of up to 1400 m/s within a distance of ～14 tube diameters are produced.     

冲击压缩下氩气辐射特性初步研究

 用二级轻气炮加载方法把平面钨飞片加速到1.78 km/s、2.00 km/s和2.76 km/s,对封装有氩气的铝材料靶盒进行碰撞,由此产生的平面冲击波加热氩气样品。通过光纤传输、六通道瞬态光学高温计和示波器系统记录冲击氩气的高温辐射历史,从而测量出气体中的冲击波速度,并观察出随冲击强度的逐渐增大时氩气发光特性的变化规律：冲击压缩下波后氩气的光辐射强度随时间变化,信号曲线从直线变为指数曲线。在一维冲击波和局域热动平衡假设下,通过简单的理论计算和分析解释了实验现象和相关的辐射机制。     

Self-similar Solution of a Cylindrical Shock Wave under the Action of Monochromatic Radiation in a Rotational Axisymmetric Dusty Gas

A self-similar flow behind a cylindrical shock wave is studied under the action of monochromatic radiation in a rotational axisymmetric dusty gas. The dusty gas is taken to be a mixture of small solid particles and perfect gas,and solid particles are continuously distributed in the mixture. The similarity solutions are obtained and the effects of the variation of the radiation parameter, the ratio of the density of solid particles to the initial density of the gas, the mass concentration of solid particles in the mixture and the index for the time dependent energy law are investigated.It is observed that an increase in the radiation parameter has decaying effect on the shock waves; whereas the shock strength increases with an increase in the ratio of the density of solid particles to the initial density of the gas or the index for the time dependent energy law. Also, it is found that an increase in the radiation parameter has effect to decrease the flow variables except the density and the azimuthal component of fluid velocity. A comparison is also made between rotating and non-rotating cases.     

一种新的光子多普勒速度频谱分析方法

光子多普勒速度计可给出飞层表面某一速度带内颗粒群速度随时间演化的频谱数据, 在冲击动力学实验尤其是微喷射及其混合研究中得到广泛应用. 本文提出一种新的光子多普勒频谱数据分析方法, 可推断出混合区厚度变化和前端等效颗粒尺度. 利用该方法, 对一些典型状态下喷射混合速度频谱开展分析, 获得了不同冲击压力、气体条件下颗粒度数据, 证实了气体环境下喷射颗粒的气动破碎现象, 以及破碎后尺度与初始条件的依赖性, 为喷射混合物理规律研究提供了重要依据.     

高气压精密漂移管的时间性能研究

对高气压精密漂移管的时间性能进行了研究.利用放射源和宇宙线对漂移电子的时间谱和带电粒子入射位置与漂移时间关系(r–t)及其诸影响因素进行了研究.分析了时间谱的拟合参数,并用积分法由时间谱得到(r–t)关系.     

反向碰撞法测量Bi的低压Hugoniot数据

在火炮和二级轻气炮上利用反向碰撞技术,通过测量飞片击靶速度以及飞片/窗口的界面粒子速度,获得了金属铋(Bi)在10-45 GPa压力范围内的Hugoniot数据. 该方法克服了电探针法在测量低压Hugoniot数据时由于导通一致性差而不能准确得到冲击波速度的难题,同时又避免了精确测量样品中冲击波走时的问题. 实验获得的冲击波速度(D)-波后粒子速度(u)Hugoniot数据表明,Bi在粒子速度u=0.9 km/s附近D-u曲线发生了明显拐折,产生这一拐折的原因推测与冲击导致的Bi的固-液相变有关. 关键词： Hugoniot数据 反向碰撞 冲击相变 铋