DⅢ—D托卡马克ELM期间密度起伏特性

在DⅢ-D中已用一种多道相位对比成象(PCI)诊断系统地研究了与ELM相关的湍流脉冲率，这种诊断对在托卡马克外边缘的密度起伏的长极向波长成分是灵敏的。湍流的时间动力学与从偏滤器得到的特征Da信号的比较已揭示I型ELM(边缘定城模)和Ⅲ型ELM之间的系统差别：即使在I型ELM前有时观察到先兆起伏，PCI信号水平在Da信号中的峰值之前仍是高的；相反，在Ⅲ型ELM中，起伏脉冲先于Da峰值0．4—0．6ms。I型ELM能在删削层中产生“回波”，即次级脉冲率。只在Ⅲ型ELM期间观察到相干模。通过对多ELMs进行平均来提高统计精确度，已重建了在瞬态ELM阶段湍流的径向和时间相关关系结构及频谱性能。发现ELM湍流与L模湍流共有许多性能，其中包括径向波数和频谱及径向色散关系的主要定性特性。然而，也确认了只有ELM湍流才有的特性。     

气-液两相临界流速及压力扰动传播规律

应用整体平均两流体模型建立了带相变的气-液两相流压力波传播模型。根据小扰动原理和一阶线性齐次方程组有解的条件导出了两相压力波的色散方程。通过理论及实验数据分析了两相临界流速和压力脉冲及压力波传播速度间的关系,并研究了泡状流和弹状流流型下气-液两相压力波的传播规律。研究结果表明:气-液两相压力波具有色散特性,当扰动频率趋于∞时压力波传播速度等同于压力脉冲传播速度;两相临界流速与压力脉冲扰动传播速度相等价。     

垂直上升管内泡状流压力波传播

研究了垂直上升管内气液两相泡状流压力波的传播速度和衰减规律,为了提高压力波测量精度．实验中设计了不影响两相流动结构的调频式压力扰动装置．实验结果表明,随着含气率的增加,泡状流中压力波波速开始陡降,当含气率大于0．05以后波速缓慢下降;衰减系数随含气率的增加连续增加：工质的流速对压力波的传播没有影响;压力波的传播速度及其衰减与扰动频率有关．随着扰动频率的增加,波速及其衰减都增加本文实验验证了泡状流压力波色散特性的临界频率现象．即高于临界频率．压力波的色散特性消失．在本试验条件和参数范围内．临界扰动角频率为300Hz．     

托卡马克逃逸电子输运系数的研究

1 对托卡马克逃逸电子的一般介绍 近期,人们对托卡马克中逃逸电子输运的研究十分重视与活跃。从欧姆加热与辅助加热的等离子体中,逃逸约束时间具有反常行为,这与内部的磁场涨落相关;我们利用逃逸电子作为一种试验粒子来诊断托卡马克内部的磁涨落。从约束的环向等离子体中观察到粒子与能量的损失率远比由新纪典输运理论所预言的要大得多,此状态取决于平均等离子体参数与库仑碰撞。若干类型的等离子体湍流提供了附加的等离子体输运。等离子体参数的涨落将通过静电涨落或磁涨落引起输运。该涨落所驱动的径向粒子通量为(1)其中,是扰动角向电场,是扰动电子密度。是     

温度噪声相关测速方法的系统误差与自标定

研究了流体噪声的湍流传递行为及信号源的性质对相关测速系统的影响，分析了相关测速系统的系统误差，并提出了理论修正该误差的方法，使得相关测速成为一种绝对的测量方法。在理论分析的基础上进行了实验研究，理论与实践得到了较好的统一。     

HL-2A芯部等离子体ITG模和TE模增长率研究

本文基于双流体模型,通过理论分析获得了芯部离子温度梯度(ITG)模和俘获电子(TE)模的色散关系。在Weiland模型的基础上,考虑了离子平行方向速度和TE的影响,计算了碰撞对ITG模和TE模增长率的影响。对HL-2A等离子体的计算结果表明,芯部等离子体的ITG模和TE模增长率与扰动波数密切相关,磁剪切对ITG模有明显的抑制作用。     

超临界条件下湍流时均化输运方程研究

为探索超临界条件下物性脉动作用于流体传质传热的机理,从Navier-Stokes方程出发,采用Reynolds时间平均和质量加权平均相结合的方法,获得考虑物性脉动的超临界条件下湍流时均化输运方程。研究表明,超临界条件下的湍流控制方程主体结构与亚临界湍流控制方程相似,只是在湍动能和湍流耗散率输运方程则新增物性脉动项。在超临界条件下这些物性脉动项不能忽略,它们会影响流体的脉动强度,改变由于流体速度脉动而发生的传质传热。     

堵塞条件下紧密栅湍流交混特性研究

开展堵塞工况下紧密栅内流体子通道间隙湍流交混研究,对事故工况下燃料组件热工水力行为的预测具有重要意义。本文采用CFD方法对紧密栅内堵塞工况的流体流动现象进行了模拟,模拟结果与相关文献结果吻合较好。进一步对比分析了不同堵塞工况下,堵塞段及堵塞下游的速度场、涡结构以及湍流交混系数分布。所得不同堵塞工况下的横向与轴向湍流交混系数变化规律,可为子通道分析程序的参数设置提供参考。     

非能动冷却系统上升通道中湍流自然对流的直接数值模拟

湍流直接数值模拟形成的数据库可以为开发功能更完善的湍流模型提供数据支撑。本文采用直接数值模拟方法研究了在不同普朗特数(Pr)下竖直通道中湍流自然对流的平均速度、平均温度、速度和温度脉动强度、雷诺应力、湍流热通量和湍流结构的分布特性。研究结果表明:(1)湍流自然对流的平均速度和平均温度分布关于通道中心线反对称,最大速度和温度梯度出现在壁面附近区域,Pr数增加,最大速度值减小,而壁面处温度梯度增加;(2)湍流自然对流的速度脉动强度、温度脉动强度、雷诺应力和湍流热通量随Pr数增加而降低,热通量在高温壁面侧会出现负值;(3)湍流自然对流的脉动速度和温度分布没有特别规则的结构,但主流脉动速度与壁面呈一定夹角。     

时间微分扰动角关联技术在材料科学中的应用

介绍了时间微分扰动角关联方法的基本原理及其在材料微观性质研究中的应用。     

Propagation of Pressure Wave in Air-Water Two-Phase System, (II)

Trends observed in the experimental data of increasing deviation of pressure wave velocity from the nonslip homogeneous model, reported in Part (I), are explained from consideration of slip between the phases. The slip reduces the inertial effect of liquid and consequently brings about an increase in the wave propagation velocity.

In order to testify quantitatively to the above interpretation by analysis of observed data, the theoretical approaches of perturbation method and Fourier transformation in time and space were applied to the fundamental equations of mass and momentum of each phase, taking the interaction between the phases as a function of the relative velocity only. The propagation velocities dependent on frequency were calculated from the characteristic equation derived by the above procedure, and fairly good agreement was obtained between theoretical and experimental data arranged with frequency as parameter.

Applicability of linearization theory and relaxation of shock formation are physically discussed, and they are attributed also to attenuation effect by slip.     

Modulational instability of the coupled waves between fast magnetosonic wave and slow Alfvén wave in the laser–plasma interaction

By performing modulational instability analysis of the the nonlinear coupled dimensionless equations between a fast magnetosonic wave(FMSW) propagating obliquely with the magneticfield and a low-frequency slow Alfvén wave(SAW), we obtain the dispersion relation of the perturbation wave. The growth rate of the perturbation wave is obtained. It is found that the growth rate increases as background magnetic field increases, which is in agreement with that reported by Tiwary et al(2016 Phys. Plasmas 23 122307). A critical perturbation wave number is found. When the perturbation wave number is greater than or equal to the critical value, the growth rate is positive and it increases as the perturbation wave number increases, while the wave is stable. The maximum growth rate is reached when the frequency of the FMSW is half of the ion cyclotron frequency. The minimum growth rate is reached when the propagation direction of the perturbation wave is the same as that of the FMSW.     

Prediction of turbulent mixing rates of both gas and liquid phases between adjacent subchannels in a two-phase slug-churn flow

This paper presents a slug-churn flow model for predicting turbulent mixing rates of both gas and liquid phases between adjacent subchannels in a BWR fuel rod bundle. In the model, the mixing rate of the liquid phase is calculated as the sum of the three components, i.e. turbulent diffusion, convective transfer and pressure difference fluctuations between the subchannels. The components of turbulent diffusion and convective transfer are calculated from Sadatomi et al.'s [Nucl. Eng. Des. 162 (1996) 245–256] method, applicable to single-phase turbulent mixing, by considering the effect of the increment of liquid velocity due to the presence of gas phase. The component of the pressure difference fluctuations is evaluated from a newly developed correlation. The mixing rate of the gas phase, on the other side, is calculated from a simple relation of mixing rate between gas and liquid phases. The validity of the proposed model has been confirmed with the turbulent mixing rates data of Rudzinski et al. [Can. J. Chem. Eng. 50 (1972) 297–299] as well as the present authors.     

A study on technique to estimate impact location of loose part using Wigner-Ville distribution

Presented in this paper is a method to estimate impact location of a loose part using the Wigner-Ville distribution. The method uses dispersion characteristics of bending waves propagated in a plate. The power propagation velocity and arrival time difference of bending waves related to the dispersion characteristics can be obtained through the transformation of impact signals using the Wigner-Ville distribution. The distance from the impact location to the signal measuring point can be estimated using the information on the power propagation velocity and the arrival time difference of two bending waves. The experimental results show that the proposed method estimates the impact location with relative percentage error within 10% compared with the actual impact location.     

Excitation and Propagetion of Modified Fluctuation in a Toroidal Plasma in KT—5C Device

Understanding the propagation of the turbulent perturbation in the tokamak edge plasma is an important issue to actively modify or control the turbulence,reduce the anomalous transport and improve plasma confinement.To realize active modification of the edge perturbation,a high dynamic output,broad-band,low-cost power amplifier is set up,and used to drive the active probes in the experiments on KT-5C Tokmak.By using small-size magnetic probes together with Langmiur probes,It is observed that the modified perturbation by the active probes with sufficiently driving power may spread with electrostatic mode,and electromagnetic mode as well.     

摇摆对过冷沸腾相分布特性的影响机理分析

采用双探头光学探针测量了摇摆条件下圆管内过冷沸腾局部空泡份额、界面面积浓度及汽泡尺寸等局部相界面参数径向分布特性，根据实验及计算结果，从汽液相界面作用力角度对摇摆运动条件下过冷沸腾相分布机理进行了分析。结果表明：摇摆条件下，浮力径向分量、升力、湍流分散力和壁面润滑力量级约为10³ N/m³，附加惯性力与其余诸力相比小2～3个量级。因此摇摆条件下过冷沸腾相分布特性主要取决于周期性波动的升力、湍流分散力、壁面润滑力及浮力径向分量之间的平衡关系。     

Study of the O-mode in a relativistic degenerate electron plasma

Using the linearized relativistic Vlasov-Maxwell equations,a generalized expression for the plasma conductivity tensor is derived.The dispersion relation for the O-mode in a relativistic degenerate electron plasma is investigated by employing the Fermi-Dirac distribution function.The propagation characteristics of the O-mode (cut offs,resonances,propagation regimes,harmonic structure) are examined by using specific values of the density and the magnetic field that correspond to different relativistic dense environments.Further,it is observed that due to the relativistic effects the cut off and the resonance points are shifted to low frequency values,as a result the propagation regime is reduced.The dispersion relations for the non-relativistic and the ultra-relativistic limits are also presented.     

Analysis of Two-Phase Liquid Metal MHD Induction Converter

An analysis is made on the performance characteristics of a liquid-metal MHD induction converter with liquid-gas two-phase mixture as working fluid. The equivalent electrical conductivity and the velocity vary along the generator channel in this kind of induction converter.

Two important parameters which represent the variations of the equivalent electrical conductivity and the velocity respectively are defined. With these parameters the induction equation is analytically solved with the perturbation technique.

Quantities representing generator performance, such as power densities and generator efficiency, are obtained from the perturbed magnetic field and the parameters mentioned above.

Suitable combination of values for these parameters will tend to let the effects brought by the variations of electrical conductivity and of velocity cancel each other, and the relation between these parameters is analytically derived that assures the non- perturbation of the magnetic field and of the gross output power density. In this condition of non-perturbation, the generator efficiency approaches that for the unperturbed case when the velocity variation and the inlet slip ratio are small.