平行通道流动不稳定性研究

并联通道的不稳定性是两相流学科中的重要研究方向。本文针对强迫循环并联环隙窄缝通道系统,使用RELAP5/MOD3.4程序进行分析,研究了平行通道系统的流动不稳定特性。指出在加热通道的水力直径较小时,平行通道系统中存在管间脉动和管间流量漂移两种不稳定现象。根据水动力特性曲线的特性,分析了这两种不稳定现象的形成及发展过程,得出主要运行参数对平行通道管间流量漂移不稳定性的影响规律。     

Instability of diatomic deuterium in fcc palladium

To clarify some of the solid-state aspects of cold fusion in deuterated transition metal electrodes, we have carried out first-principles self-consistent total energy calculations for various configurations of atomic and diatomic deuterium inside fcc palladium. We find that the stability of the Pd+D system is controlled by the relative position of the deuterium-inducedantibonding level with respect to the Fermi energy. The equilibrium D-D distance in dense PdD up to =3 is found to be much larger than the free space value. The calculated Born-Oppenheimer energy surface of diatomic D₂ in crystalline palladiuim is shown to have but metastable local minima whose internuclear separation is at least 0.2 Ålarger than that of the isolated D₂ molecule. We conclude that D₂ incrystalline Pd will have a substantially lower tunneling probability than hitherto thought and that explanation for fusion mechanisms should be sought elsewhere.     

直流沸腾系统不稳定性分析

根据直流沸腾系统的特点．采用了以集中参数和可移动边界为特征的简化动态模型．推导出了两相流反馈系统。利用自动控制中的频域理论以及MATLAB软件的不稳定性分析语句和Tool Box中的Simulink工具,对其进行了分析和仿真．并得出了几种主要因素影响下的稳定性边界曲线：     

自然循环静态流动不稳定研究

研究了发生静态流量漂移时自然循环系统中流量和加热段进出口温度的变化规律及静态流漂移过程中发生的动态流量振荡现象。研究结果表明：在发生静肪流量漂移时，系统循环流量下降，、加热段的进口温度下降而出口温度上升；当静态流量漂移一段时间后，伴随着静态流量漂移，系统内同时发生动态流量振荡。在对现象描述的基础上，阐述了静态流量漂移发生的机理。     

Internal Kink Instability in Shaped Tokamaks

A criterion of an ideal internal kink mode is derved for a shaped tokamak configuration in which q-profile is very flat in the core region.A combining criterion is obtained including the necessary criterion of Mercier and the sufficient criterion of Lortz.The new criterion makes progress compared with the necessary criterion of Mercier.In the elongated plasma.a polidal beta can cause instability,while the triangularity has a stabilizing effect.The result is applicable for DⅢ-D and SUNIST.     

水平管冷凝流动不稳定性分析

通过搭建水平管模型,采用RELAP5程序模拟计算了冷凝管内冷凝流动不稳定性现象,程序计算的稳定性边界与Bhatt理论稳定性公式计算结果符合良好。瞬态分析结果表明,冷凝管内气体压力与两相段长度不匹配是造成冷凝流动不稳定性的主要原因,进而引起冷凝出口流量震荡。冷凝管参数影响分析表明,更小的流动管径与更大的流通截面积有助于冷凝流动稳定,而入口流量的影响则相对复杂。     

Rayleigh-Taylor不稳定性的MPS数值模拟

移动粒子半隐式法(MPS法)是一种适用于不可压缩流体流动计算的无网格粒子法,它采用完全的拉格朗日描述定义流体的运动,将流体离散为可移动的粒子,流体控制微分方程转化为粒子间的相互作用。本文采用MPS法对Rayleigh-Taylor不稳定性进行了二维数值模拟。结果表明,在不稳定性发展的前期阶段,当扰动振幅远远小于扰动波长时,流体界面的小扰动具有指数增长形式,与经典的线性理论分析结果一致。非线性发展阶段,所得到的气泡和尖钉的部分特征与实验结果相吻合。     

General Description of Ideal Tokamak MHD Instability Ⅱ

In this subsequent study on general descripiton of ideal tokamak MHD instability,the part II,by using a coordinate with rectified magnetic field lines,the eigenmode equations describing the low-mode-number toroidal ALfven modes(TAE,and EAE) are derived through a further expansion of the shear Alfven equation of motion.     

53.667 MHz重离子RFQ的不稳定性研究

采用多粒子跟踪程序BEAMPATH对53.667 MHz RFQ进行模拟计算,基于RFQ腔体冷测、机械测量的结果,在考虑其入口束流不稳定性、电压不平整度、高频系统稳定度、加工误差、安装误差等因素的情况下,对RFQ的出口束流品质和不稳定性进行了系统分析。结果表明,在现有的加工、安装水平下,提高RFQ入口束流稳定度和高频系统稳定度对束流在RFQ中的传输十分必要。     

环隙窄缝通道管间脉动不稳定性分析

针对套管式直流蒸汽发生器传热管环隙窄缝通道的流动,利用RELAP5/MOD3.4程序进行计算分析,讨论了节点数目和并行通道根数对流动不稳定起始点的影响。结果表明：在利用程序进行计算前需对所分析问题的节点数目进行优化选取。根据优化结果,分析了套管式直流蒸汽发生器平行通道的流动不稳定性,得出了进出口节流、进口欠热度、系统压力、进出口段长度、不均匀节流、不均匀加热等因素对环隙窄缝多通道流动不稳定性的影响。     

蒸汽发生器强迫循环流动不稳定性分析

介绍了蒸汽发生器强迫循环下稳态和瞬态的计算方法.从基本的守恒方程出发,充分考虑了蒸汽发生器的结构和可能的流动状态以及换热形式,建立了一套完整的数学计算模型.程序采用Gear算法,通过理论计算得到了流动不稳定性脉动曲线和相应的不稳定区域.本文还研究了压力、质量流速、进口过冷度和进、出口节流对不稳定性的影响.     

A Transient Modal Analysis of a BWR Instability Event

To solve the time dependent neutron diffusion equation a modal method, based on the expansion of the neutronic flux in terms of the dominant Lambda modes of a static configuration of the reactor is presented. This method is used to analyse transients of a nuclear power reactor where an instability event can be developed. A simulation of a transient with the same conditions given for the case 9 of Ringhals stability benchmark has been analysed. It is shown that with these conditions an out of phase oscillation associated with the two first azimuthal modes can be developed. These results are corroborated using a power modal decomposition, using the local power distribution provided by RAMONA code. To complete the analysis, the modal feedback reactivities have been calculated to study the coupling mechanism among modes.     

Mode-Coupling Analysis of Parametric Decay Instability in Magnetized Plasmas

In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability （PDI） in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode （O-mode） or extraordinary mode （X-mode） wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.     

基因组不稳定性与辐射致癌

辐射可以诱导受照细胞及子代基因组不稳定性的发生。基因组不稳定性导致基因的突变率增加,并通过多种机制致癌。本文简要介绍了基因组不稳定性的可能机制,及其在辐射致癌中的作用。     

APROS程序在超临界水流动不稳定性分析中的适用性研究

围绕超临界水冷堆中可能存在的流动不稳定性,采用系统分析程序APROS对不同情况下可能存在的密度波不稳定性进行分析。在APROS程序中分别对并联双通道、单通道和自然循环回路进行数值建模,采用动态求解得到各自的流动不稳定边界。结果表明,APROS程序能有效地预测超临界水流动不稳定边界,计算结果与已有的实验和数值分析结果吻合较好;在数值求解时需要优化时间步长,较大的时间步长会带来耗散效应。     

Revisiting the Effects of Compressibility on the Rayleigh-Taylor Instability

The effects of compressibility on the Rayleigh-Taylor instability （RTI） are investigated. It is shown that the controversy over compressibility effects in the previous studies is due to improper comparison, in which the density varying effect obscures the real role of compressibility. After eliminating the density varying effect, it is found that the compressibility destabilizes RTI in both the cases of constant density and exponentially varying density when M 《1. This destabilizing effect is more important at smaller values of the Atwood number AT or greater values of gravity g, and the increment in the growth rate produced by compressibility depends inversely on the pressure p or the ratio of specific heat F.     

电离辐射诱发的基因组不稳定性和旁效应

近10年来,对于基因组不稳定性和旁效应的研究已成为生物学和放射生物学领域的一个热点。随着对辐射损伤研究的深入,电离辐射引起的非靶效应（如基因组不稳定性、旁效应等）将对与辐射照射有关的危险评价提出新的挑战。本文就体内、外电离辐射诱发的基因组不稳定性,体内、外旁效应以及二者之间的关系做一简要概述。     

平行通道密度波不稳定性研究

本文针对套管式直流蒸汽发生器传热管环隙窄缝通道的流动,采用RELAP5程序对强迫循环并联通道的流动不稳定现象进行研究,指出在进口欠热度较低的条件下,并联通道系统会发生两种完全不同的不稳定现象,即同相密度波不稳定性和管间脉动不稳定性。对密度波不稳定性的发生条件进行研究,在较大的参数范围内确定了各系统参数的影响规律,最终得出流动不稳定边界。并对不同流量条件和不同压力条件下的不稳定性区间进行了比较。