气/液两相泡状流相关流速测量系统的研究

气/液两相流是自然界和工业过程中一种非常典型、复杂的多相流形态,其中,离散相如气泡的运动速度、尺寸、位置以及两相流流型等参数的监测是一个很重要的研究课题.本文介绍了利用电容层析成像技术和相关流速测量技术对气/液两相泡状流的离散相速度及其分布测量的研究.     

气固两相流电容相关流量测量仿真研究

以气/固两相流互相关测量系统为研究对象,采用计算机仿真的方法,对由电容传感器构成的基于离散相浓度的电容互相关流速测量机理进行研究。利用ANASYS软件分析电容传感器与离散相浓度的关系;采用Monte-Carlo方法,建立气/固两相流动模型;研究"凝固流动图型"、"非凝固流动图型",离散相浓度、粒度及速度分布对互相关测量系统的影响。     

相关流量测量系统的仿真研究

叙述了对两相流相关流量测量系统进行蒙特卡洛模拟的方法,并给出了脉冲超声相关流量计测量气/液两相泡状流的仿真研究结果。     

PIV应用于气液两相流的研究现状

作为一种全新的无扰、瞬态、全场速度测量技术,粒子图像测速(PIV)技术近年来在单相流和多相流领域得到了广泛的应用.对于气液两相流PIV技术,目前还处于起步与发展阶段.着重概述了两相示踪粒子的采样技术,并对近年来国外PIV技术在气液两相流动领域中的研究现状做了总结与分析,指出PIV技术在气液两相流体特性研究中具有很好的应用前景.     

气液两相流红外检测技术研究

气液两相流检测是目前载人航天电解制氧装置急需解决的关键技术之一。设计一种基于红外检测的传感器实现对低浓度液/气含量的测量,通过对脉宽调制(PWM)驱动红外发射、TEC恒温控制、抗干扰等技术研究,成功制得气液两相流传感器。实验表明,该传感器可测量液态水含量0～30%的气液两相流,系统误差优于10%,能够满足电解制氧装置两相流检测的需要。     

智能化流量测量相关仪

相关流量测量法是解决两相流测量等困难流量测量的有力手段，本文采用了新的高速极性相关算法，实现了以该算法为基础的智能化八通道流量巡回检测用相关仪。实验及现场使用证明，该相关仪具有良好的实时性。它与电容传感器配合，可以测量气／固两相流的流量。     

电容层析成像技术在油/气两相流可视化监测中应用

介绍电容层析成像系统的基本原理，着重介绍了一种基于正则化修正的图像重建算法，危重利用电容层析成像系统进行油／气两相流成像实验，初步的实验结果表明，采用该技术可以较好地实现对油／气两相流可视化监测。     

气液两相流空隙率测量方法微重力环境应用研究

微重力环境下气液两相流空隙率测量是载人航天器需解决的关键技术之一。通过对当前常重力环境下气液两相流空隙率测量方法的特点和微重力环境对气液两相流空隙率测量的影响分析,提出了满足微重力环境气液两相流空隙率测量方法的基本要求,对当前空隙率测量方法在微重力环境应用的可行性进行了分析,并给出了相应建议。     

槽式孔板的气液两相流测量特性

为了准确计量气液两相流量,选用槽式孔板作为一次传感元件、以空气/水为测量介质,进行了一系列的实验.介于两相流动的随机波动特征,对气液两相流流过槽式孔板时产生的差压信号进行了处理,提取出能够反映气液流量变化的几个统计特征量,总结了差压信号的平均值、标准差、自相关最大值和(0,4)Hz频段功率随气液流量变化而变化的规律,为两相流流量计的开发奠定了基础.     

基于电容层析成像技术的两相流可视化测量仪器

针对油水两相流参数测量问题,依据二重积分微元原理建立了油水两相流分布信息的数学模型,采用一种具有抗杂散电容的测量电路和80C32单片机完成了极板间电容的测量和采集系统的控制,组建了一套8电极油水两相流电容层析成像测量系统,系统采用了自适应阈值的图像重建的方法完成了油水两相流的截面图像的重建和油水两相流含水率的计算,其重建精度在1%左右,满足了油水两相流流型识别的要求,为油水两相流参数的可视化测量提供一种新方法.     

基于相关算法的电磁流量计抗噪性能研究

针对电磁流量计在低速测量时,信号被噪声淹没不能准确测量的问题,引入了相关检测算法.本文介绍了相关检测算法进行流量测量的基本原理,通过在电磁流量计测量中引入相关检测算法,滤掉了噪声干扰,提高了信号的信噪比,使电磁流量计在低速或者在低信噪比的情况下测量时,性能有较大改善,精度可达0.5%左右.在低流速时能够稳定的显示数据.     

基于环形像素点匹配的快速图像跟踪算法

相关跟踪法能有效地跟踪目标,但非常费时。序贯相似检测法结合了粗-精搜索策略,在跟踪性能和时间上都有很大改进,但在处理时间上还有进一步提高的可能。基于特征点的跟踪方法在跟踪时运算量小,但提取目标的特征时需要大量运算,且特征点的提取往往不理想。针对以上不足,论文提出了基于环形像素点匹配的快速图像跟踪算法,该算法采用环形像素点为特征点,在借鉴序贯相似检测法的基础上,对匹配区域先进行粗搜索以确定待匹配窗口,再进行精搜索以确定正确的匹配窗口,最后利用相关跟踪法中的归一化相关系数确定模板的更新策略。实验结果表明,该算法不仅能稳定地跟踪目标,与相关跟踪法和序贯相似检测法相比,在处理时间上具有明显的优越性。     

Simulations of lateral mixing in cross-channel flow

Cross flow phenomena between connected sub-channels are studied by means of numerical simulations based on lattice-Boltzmann discretization. The cross (that is lateral) transfer is largely due to macroscopic instabilities developing at two shear layers. The characteristic size and advection velocity of the instabilities favorably compare with experimental results from the literature on a geometrically similar system. The strength of the cross flow strongly depends on the Reynolds number, with cross flow developing only for Reynolds numbers (based on macroscopic flow quantities) larger than 1360. Mass transfer between the sub-channels has been assessed by adding a passive scalar to the flow and solving its transport equation. As a result of the intimate connection of cross flow and lateral mass transfer, also the mass transfer coefficient is a pronounced function of Re.     

基于MapX的河道输水动态模拟系统的研究与实现

通过对可视化技术的研究,以水力模型为基础,采用Visual Basic、MapX和SQL Server相结合的可视化开发环境研发了河道水流演进动态模拟系统,实现了模拟河道水流在不同边界条件下的演进过程,提供了任一时刻、任一断面的水位和流量,进而通过时间序列,在计算机屏幕上以图示的形式反映各断面水位和流量的演化过程.     

On the Nonlinearity and Correlation Immunity of Two Classes of Boolean Functions

Recently, Liu et al. have proved a class of 2k-variable Boolean functions to have optimal algebraic immunity and good immunity to fast algebraic attacks. In this paper, we proceed to study those functions in aspect of correlation immunity and nonlinearity and through restrictions to those functions we propose two sub-classes of 2k-variable Boolean functions with good cryptographic properties. To the best of our knowledge, this is the first time whole classes of Boolean functions with high nonlinearity, 1-correlation immunity and good immunity against FAA can be found.     

Non-Newtonian flow in pipes of non-circular cross section

Rectilinear flow through pipes of non-circular cross section in the case of elastico- viscous liquids is not possible in general and some secondary flow in the cross section of the pipe is to be expected. The present paper contains a detailed theoretical and experimental study of the problem for pipes of square and rectangular cross section. Our main concern is the form that the secondary flows take and their influence on the flow rate through the pipe.

The governing equations, which are non-linear partial differential equations, are solved numerically using finite difference methods used in conjuction with S.L.O.R. It is shown, that, for both the square and rectangular cross sections, there are eight vortices present. These have the same strength for the square cross section, but four of the eight become progressively weaker as the ratio of the sides of the rectangle is increased.

The effect of a variable (shear-dependent) viscosity on the flow rate is found to be sub- stantial but the effect of the secondary flows on the flow rate is predicted to be small unless the fluid has some rather unusual properties

The experimental results are in general agreement with the theoretical predictions.     

Computational study of effect of tabs on a jet in a cross flow

A three-dimensional viscous flow analysis is performed using a time-marching Reynolds-averaged Navier-Stokes code for the case of a jet in a cross flow with a delta tab placed on the windward side of the jet to inhibit mixing for film cooling applications. The flow configuration which was previously studied experimentally, involved a jet discharging normally from the floor of the wind tunnel test section into the cross flow with a momentum ratio (jet/cross-flow) of 36. The computed results are compared with the experimental data which include streamwise velocity and vorticity distributions at various axial locations downstream of the jet. The computational results show reasonably good agreement with the experimental data.     

Optimization of bistable viscoelastic systems

We consider the flow of a viscoelastic fluid in a symmetric cross geometry. For small driving pressures the flow is symmetric, but beyond a certain critical pressure the symmetric flow becomes unstable; two stable asymmetric solutions appear, and forcing of the unstable symmetric flow beyond the critical pressure gives rise to increased hydraulic resistance. We have combined a state-of-the-art implementation for viscoelastic flow modeling with topology optimization in a high level finite element package (COMSOL). We use this framework on the cross geometry with the aim to reduce the critical driving pressure corresponding to the point of bistability, such that the effect is enhanced. The point of bistability is, however, not explicitly contained in the solution, so we opt for a heuristic approach based on the dissipation ratio between the asymmetric and unstable symmetric flow solutions. We find a design that significantly reduces the driving pressure required for bistability, and furthermore is in agreement with the approach followed by experimental researchers. Furthermore, by comparing the two asymmetric solutions, we succesfully apply the same approach to a problem with two fluids meeting in the cross.     

流量装置流量稳定性数值仿真评价方法研究

为了提高装置流量稳定性,提出基于计算流体动力学（ CFD）仿真,采用轴向动量数KU、旋流数KV 和不对称数KA ,分析管路不同截面位置的流场速度特征,利用多个截面位置的特征参数变化,评价装置管路的流量稳定性。对新建水装置流量稳定性进行数值仿真分析与实验测试,得出一致性结论。该方法可以在装置设计阶段,对流量稳定性进行评价,从而优化管路结构,提高装置流量稳定性。     

重油输送系统基于流量-压力的建模与仿真

应用于阳极焙烧的重油输送的精确控制是一个典型交叉耦合的复杂控制问题，它对炭阳极焙烧质量起关键作用，输送过程中涉及到重油流量、压力和温度三个参量的变化。为了简化所建模型，假定重油输送过程中油温恒定，这样在建模过程中就剩下重油流量与压力之间的耦合关系。为了实现阳极焙烧重油输送的精确控制，通过对阳极焙烧重油输送工作机理的分析。以现场实际采集的数据为基础，采用管道流体传输的物理机理建立对象的模型的方法，提出了一种阳极焙烧萤油输送的基于流量-压力精确控制的数学模型，经仿真验证了该模型的有效性。