About the equilibrium and stability of the magnetopause

This paper offers a model of the magnetopause based on the theory of the contact discontinuity; the boundary layer between the two states of space plasma. The structure of the magnetopause is explored for the effects of polarization, and the profiles of the polarizing electrostatic field are obtained.     

About the equilibrium and stability of non-electroneutral current sheaths

In this paper, we prove the necessity of using the Cauchy problem, i.e., initial value problem, for solving the equilibrium (steady state) current sheet. In this connection, it appears that equilibrium current sheaths exhibit structural instability.     

Atomization mechanism of a charged viscoelastic liquid sheet

In order to study atomization mechanism of a viscoelastic liquid sheet in an electric field,the spatial–temporal stability analysis of a viscoelastic liquid sheet injected into a dielectric stationary ambient gas in the presence of a vertical electric field is conducted. The dispersion relations of both sinuous and varicose disturbance modes are solved to explore the spatial–temporal instability of a charged viscoelastic sheet, by setting both the wave number and frequency complex. A parametric study is performed to test the influence of the dimensionless parameters on the absolute instability of the sheet. The results show that the increase of liquid Weber number and time constant ratio, or decrease of gas to liquid density ratio and Reynolds number, can damp the absolute instability. The effect of the liquid elasticity depends on the value of time constant ratio: when time constant ratio is small, the increase of liquid elasticity could amplify absolute growth rate, but the effect is weak when the elasticity number is relatively large; when time constant ratio is large, the increase of liquid elasticity cannot affect the absolute growth rate. Moreover, the variation of electrical Euler number can hardly influence the absolute instability of a charged viscoelastic sheet.     

蒸发式稳定器燃烧不稳定性初步研究

对蒸发式火焰稳定器结构的模型燃烧室进行了燃烧不稳定性实验。实验中选取了3个当量比,分别为0.4545,0.5454,0.6363。每一个当量比中,值班级供油的比例从2%变化到36%,间隔为2%。利用动态压力传感器测量了不同当量比以及不同值班级供油比例时燃烧室内动态压力的频率和振幅。为了进行对比,在以上3个当量比时,也对普通V型稳定器进行了实验。结果显示,蒸发式稳定器激发了130Hz和203Hz两个不稳定模态。V型稳定器只激发了203Hz一个不稳定模态。总当量比不变时,随值班级供油比例的增加,除当量比0.6363工况的203Hz模态振幅呈现减小趋势,其他燃烧不稳定性模态的振幅均先增大后减小。对燃烧室进行了一维声学模态分析,130Hz和203Hz模态分别为系统的第2和第3阶纵向模态。     

低雷诺数下跨声速转子周向槽处理机匣扩稳研究

采用数值方法模拟了低雷诺数条件下NASA Rotor 37跨声速压气机转子内部流场。结果表明,附面层径向涡是该压气机转子流动失稳的一个很重要的原因。周向槽处理机匣结构对压气机流场的改善较为有限,而引入抽吸处理机匣后,抽吸槽可以将叶顶间隙涡和附面层径向涡及其引发的低能阻塞流团抽吸至处理槽内,叶顶流场大为改善,有效地提高了压气机转子的失速裕度。     

旋转飞行器固体火箭发动机内涡核流动的数值分析

为分析旋转飞行器固体火箭发动机内涡核流动,采用数值计算的方法对发动机流场进行模拟。计算结果显示发动机的旋转增强了轴向涡核流动,随着涡核的不断延伸,在喷管入口处,由于潜入式喷管结构以及喷喉直径较小,振荡运动随之加强。涡核在流经喷管时的不断增强,在喷管区域形成了非对称的压力形式,并且产生了实际中的扰动侧向力,最终导致了飞行器的章动不稳定性。     

等离子射流在圆柱充液室中扩展、掺混的实验及数值模拟

为了研究等离子射流与液体工质相互作用特性,设计了圆柱型充液室,运用数字高速录像系统观察了等离子射流的扩展过程,重点研究了放电电压对等离子射流扩展特性的影响。实验结果表明,等离子射流在液体中扩展时,两相流体存在较大的速度差,Taylor-helmholtz不稳定效应导致强烈的两相湍流掺混,Taylor空腔的亮度在时空上呈非单调分布;放电电压越大,Taylor-helmholtz不稳定效应越强。在实验基础上,建立了等离子射流扩展的二维轴对称非稳态可压缩流的数学模型,并进行了数值模拟,获得了射流场中Taylor空腔界面的形态变化,以及流场中压力、速度、温度、湍动能和湍流耗散率的分布特性。由Taylor空腔界面扩展云图计算得到的Taylor空腔轴向扩展位移与实测值吻合较好。     

某型液体火箭发动机燃烧不稳定性鉴定实验研究

采用脉冲枪装置,在液体火箭发动机燃烧室中产生燃烧波,对发动机燃烧过程进行人为激励;通过实验参数测量系统,测量激励前后燃烧室的脉动压力和机械振动频率等参数,分析燃烧室脉动压力的振荡衰减率,进行发动机燃烧不稳定性鉴定实验研究.结果表明:该型液体火箭发动机燃烧过程对脉冲扰动是稳定的.     

边界形状影响等离子体射流扩展特性的实验研究

为了探索燃烧室边界形状在控制燃烧稳定性方面的特性,设计了圆柱型和圆柱渐扩型充液室,运用高速录像系统研究了等离子体射流在充液室中的扩展过程。结果表明：等离子体射流在液体工质中扩展时,等离子体一液体两相流体速度差较大,TaylorHelmh01tz不稳定效应强烈,圆柱型充液室中,Taylor空腔界面自由,界面增长随机脉动性较大;渐扩型充液室能够使两相流边界受到约束,使Taylor空腔沿着充液室边界逐级扩展,从而减弱了Taylor-Helmholtz不稳定效应,有效抑制了界面增长的随机脉动性。放电电压、喷嘴直径和渐扩结构因子△D／L对Taylor空腔扩展过程均有不同程度的影响,通过对这些参数的优化匹配,可以在一定程度上实现对射流扩展过程的控制。     

Spectrum of global ideal-magnetohydrodynamic three-dimensional ballooning modes

The class of pressure-driven plasma instabilities known as ballooning modes may be responsible for such diverse phenomena as high-beta disruptions in tokamaks, solar flares and magnetospheric substorms. In this paper the theory of the spectrum of unstable eigenvalues of the linearized ideal magnetohydrodynamic (MHD) equations of motion in non-axisymmetric toroidal equilibria is sketched, comparing and contrasting systems with open field lines and systems with toroidally confined field lines. The need to regularize ideal MHD to keep the wavenumber finite, and the relevance of quantum chaos theory to understand the structure of the spectrum, is pointed out. This revised version was published online in August 2006 with corrections to the Cover Date.