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1.
结合严重段塞流的形成机理,研究了立管底部压力与集输管道中流体压力的变化规律,建立了过渡流型向严重段塞流、稳定流转变的准则模型。对比Lockhart-Martinelli参数法和Beggs-Brill公式法在气液两相流含气率的预报效果,并将流型转变模型的预报结果与实验结果对比,结果表明:采用Beggs-Brill公式计算气液两相流含气率时具较高的精度,同时本文流型转变预报模型的预报值与实验结果吻合很好,从而可以为海洋集输立管系统的优化设计提供理论依据。  相似文献   

2.
差压法测量两相流相含率的研究   总被引:8,自引:0,他引:8  
本文通过差压式测量方法,对气液两相流中含气率及油水两相流中含水率的测量进行了深入的试验研究。通过水平及垂直上升段的结构组合,测量气液两相流中的含气率值,在对流型测量与分析的基础上,建立了不同流型下垂直上升段与水平段摩擦压降间的修正关系式,减小了测量误差;通过采用一缓流的垂直下降段,测量油水两相流中的含水率值,获得了好的结果。  相似文献   

3.
分层流是气液两相流中常见的流动型式,分层流中液层高度是计算的基本数据,由于界面波的存在,对液层的测量和预测都很困难.Vlachos提出了预测气液两相分层流液层厚度的关系式,但这一关系式并不适用于倾斜下降管气液两相流.本文提出了计算倾斜下降管气液两相分层流截面含气率的理论模型,在这种模型下得到的截面含气率和实验结果符合良好.在大量实验的基础上,考虑了倾角、管径、气液各相折算速度的影响,根据实验数据提出了预测液层厚度的关系式。  相似文献   

4.
垂直上升矩形截面管内的气液两相流横向冲刷水平布置的柱体时,一定条件下会在柱体后部产生旋涡交替脱落现象,使柱体在与来流垂直的方向上受到脉动升力的作用。本文以截面分别是方形、正三角形的柱体为例,研究了这种带锐缘的柱体在气液两相流中受到的脉动升力,得出了涡街的Strouhal数和柱体的脉动升力系数C'L随Re数和来流含气率。的变化情况。实验结果表明:在本文的实验范围内,方形柱体和正三角柱体的Strouhal数不随Re数变化,而在一定的含气率范围内,随着含气率的增大而增大;C'L也不随Re数而变化,而随着来流含气率的增大相减小而后很快增大。  相似文献   

5.
气液两相流体绕方柱流动的数值模拟   总被引:1,自引:0,他引:1  
本文详细给出了气液两相流动双流体模型下的各控制方程组和相间作用力,通过将气泡引起的紊流与剪切引起的紊流线性叠加给出了气液两相流动的紊流模型。通过给出的边界条件,采用ITA-IPSA算法对垂直上升的气液两相流横向冲刷方柱引起漩涡证替脱落的过程进行了数值模拟,得到了流场和局部含气率变化的示意图,数值模拟与试验的结果基本一致。  相似文献   

6.
零净液流量两相流持液率与阻力特性研究   总被引:1,自引:0,他引:1  
分别以牛顿流体和非牛顿流体为液相,研究了垂直管中零净液流量气液两相流的流动特性。提出了零净液流量气液两相流动模型,应用这一模型计算了零净液流量气液两相流的持液率和压力降,模型计算结果与试验结果相符。研究结果表明,零净液流量气液两相流与常规气液两相流相比具有特殊性,表现为其持液率仅由质量平衡方程控制,其摩擦阻力压力降为负值。  相似文献   

7.
本文对注入气泡的黏弹性流体气液两相泡状流混合层流动进行实验研究,含气率为0.5%。与纯水气液两相流相似,气泡的注入也会削弱黏弹性流体中的涡结构,影响大涡的卷起。雷诺应力与涡量的分布规律类似,其峰值集中在混合层中心区域。注入气泡使混合层中心区域内的雷诺应力增大,峰值区域范围减小,添加聚合物的混合层中的雷诺应力峰值增大得更多。对涡量而言,注入气泡使峰值产生非常明显的减小,黏弹性流体的涡量所受的影响比纯水的要小。  相似文献   

8.
以一台自主研发的螺旋轴流泵为研究对象,以水和空气的混合物为介质,采用高速摄影技术,研究了不同工况下泵入口段及第一级叶轮内部的气液两相流型。研究发现:入口段气液两相流型为均匀的泡状流,气泡直径随入口含气率的增加而增大,随转速的增加而减小;随着入口含气率的逐渐增加,叶轮内分别出现了孤立的气泡流、泡状流、气囊状流及乳化状流;气囊出现在叶片压力面约2/3弦长的位置,且紧贴着叶轮轮毂;出现气囊状流时,泵的性能下降最为明显;出现乳化状流时,随着含气率的增加,增压性能下降趋于缓慢。  相似文献   

9.
螺旋管内气-液两相流截面含气率试验研究和理论模型   总被引:1,自引:1,他引:0  
1前言关于螺旋管内气-液两相截面含气率的预报是一个重要的课题。即使只考虑平均截面含气率,也有气液两相间的滑移、各相流速和气相沿流通截面的不均匀分布等影响因素。查阅有关文献[1,2],对螺旋管内气-液两相截面含气率的研究还很不够。因此,本文重点从二方面进行了研究。首先借助快速关闭球阀法,得出三根不同螺旋管平均截面含气率的试验测定结果,考查了螺旋升角和螺旋直径对其产生的影响;其次,按不同流型,依据“分相动量模型”和“漂移流率模型”、得出计算螺旋管内主要流型平均截面含气率的经验关系式。本文研究对象:三…  相似文献   

10.
王建涛  刘刚  江雄  牟斌 《气体物理》2016,1(3):31-38
文章通过对EFM(effective field modeling)模型进行简化, 消除了原模型的非守恒性项和非双曲性特性项, 发展了一种基于密度的气液两相流模拟方法: ρ-VOF方法.利用体积分数信息对控制单元内的自由界面进行重构, 得到了控制单元内流体的空间分布, 并采用AUSM+-up格式获得考虑气液流体接触间断信息的对流通量.新方法可统一处理激波间断和接触间断的相互作用, 保持自由界面的尖锐性, 并且其计算量与自由界面的空间复杂度无关.最后, 数值模拟了液体激波管气液激波管和气体激波跨二维液滴传播等问题, 并与文献结果进行对比, 验证了本方法在气液两相流模拟中的准确性.   相似文献   

11.
G. Lucas 《显形杂志》2006,9(4):419-426
Upward inclined gas-liquid flows are frequently encountered in the oil industry and data relating to the local gas volume fraction distribution and the local gas velocity distribution is important, for example, in pressure gradient prediction and in modeling oil well ‘blowouts’. In this paper measurements are presented of the local gas volume fraction distribution and the local axial gas velocity distribution which were taken in bubbly air-water flows in an 80 mm diameter pipe which was inclined at angles of 0°, 15° and 30° to the vertical. Qualitative arguments are presented to explain the influence of the liquid superficial velocity on the local gas volume fraction distribution in inclined flow and also to explain the very high axial gas velocities observed towards the upper side of the inclined pipe.  相似文献   

12.
The Boltzmann simplified velocity distribution function equation describing the gas transfer phenomena from various flow regimes will be explored and solved numerically in this study. The discrete velocity ordinate method of the gas kinetic theory is studied and applied to simulate the complex multi-scale flows. Based on the uncoupling technique on molecular movement and colliding in the DSMC method, the gas-kinetic finite difference scheme is constructed to directly solve the discrete velocity distribution functions by extending and applying the unsteady time-splitting method from computational fluid dynamics. The Gauss-type discrete velocity numerical quadrature technique for different Mach number flows is developed to evaluate the macroscopic flow parameters in the physical space. As a result, the gas-kinetic numerical algorithm is established to study the three-dimensional complex flows from rarefied transition to continuum regimes. The parallel strategy adapted to the gas-kinetic numerical algorithm is investigated by analyzing the inner parallel degree of the algorithm, and then the HPF parallel processing program is developed. To test the reliability of the present gas-kinetic numerical method, the three-dimensional complex flows around sphere and spacecraft shape with various Knudsen numbers are simulated by HPF parallel computing. The computational results are found in high resolution of the flow fields and good agreement with the theoretical and experimental data. The computing practice has confirmed that the present gas-kinetic algorithm probably provides a promising approach to resolve the hypersonic aerothermodynamic problems with the complete spectrum of flow regimes from the gas-kinetic point of view of solving the Boltzmann model equation. Supported by the National Natural Science Foundation of China (Grant Nos. 90205009 and 10321002) and the National Parallel Computing Center  相似文献   

13.
气液混输管线与立管系统严重段塞流数值研究   总被引:1,自引:0,他引:1       下载免费PDF全文
高嵩  李巍  尤云祥  胡天群 《物理学报》2012,61(10):104701-104701
针对气液混输管线与立管系统严重段塞流问题, 采用严重段塞流形成条件一致的等效原则, 发展了一种将三维管道系统等效为二维管道系统的计算流体力学(CFD)数值模拟方法. 以文献中某下倾管与立管组合系统为对象, 结合其实验工况, 对严重段塞流气液流动过程进行了数值模拟, 获得了其周期、压力波动幅值及喷发时间等关键参数的变化规律, 数值模拟与文献所述实验结果符合. 在此基础上, 建立了立管入口气液折算速度、立管含气率以及立管出口平均速度的理论模型, 获得了这些关键参数随时间的变化规律, 并给出了确定立管内气液流型变化的理论方法, 理论结果与CFD数值模拟结果一致. 建立的CFD方法大幅缩减了严重段塞流数值模拟所需的时间和资源, 推导的理论模型揭示了严重段塞流特性参数之间的关联, 可以对严重段塞流所引发的危害进行快速评估及预测,具有一定的工程应用价值.  相似文献   

14.
Enhancement of gas phase heat transfer by acoustic field application   总被引:1,自引:0,他引:1  
Komarov S  Hirasawa M 《Ultrasonics》2003,41(4):289-293
This study discusses a possibility for enhancement of heat transfer between solids and ambient gas by application of powerful acoustic fields. Experiments are carried out by using preheated Pt wires (length 0.1-0.15 m, diameter 50 and 100 micro m) positioned at the velocity antinode of a standing wave (frequency range 216-1031 Hz) or in the path of a travelling wave (frequency range 6.9-17.2 kHz). A number of experiments were conducted under conditions of gas flowing across the wire surface. Effects of sound frequency, sound strength, gas flow velocity and wire preheating temperature on the Nusselt number are examined with and without sound application. The gas phase heat transfer rate is enhanced with acoustic field strength. Higher temperatures result in a vigorous radiation from the wire surface and attenuate the effect of sound. The larger the gas flow velocity, the smaller is the effect of sound wave on heat transfer enhancement.  相似文献   

15.
Results of an experimental investigation of heat and mass transfer and wall shear stress at gas-liquid flow in a vertical tube are presented. Local wall shear stress and mass transfer coefficients were measured by an electrochemical method. Experiments were performed in the range of Reynolds number variation with respect to liquid Rci, = 8.5 × 103-5.4 × 104, gas Reg = 3 × 103-1.4 × 105, pressure 0.1-1 MPa. The relationship between heat and mass transfer and wall shear at gas-liquid flows is shown to exist. The results of measuring heat and mass transfer coefficients are generalized by formulas applied to calculate heat and mass transfer in single-phase turbulent flow.  相似文献   

16.
为解决气液分离问题,提出了粒径可控离心分离的设想,即通过某种雾化技术产生粒径可控的液滴,然后根据液滴的粒径确定气液分离所需要的离心力,在高速旋转的叶片所产生的离心力作用下液滴一边与气流发生反应一边完成气液分离。为验证这一思想,搭建了一台旋流喷雾式单重态氧发生器(TFA-SOG),并通过计算流体力学模拟和实验对这台TFA-SOG进行了研究。研究结果表明,模拟的气液分离效率与实验的相一致,粒径可控离心分离的设想是可行的。  相似文献   

17.
A study of the structure of electrohydrodynamic flows shows that the electric charge carriers are ions that are practically frozen into the surrounding liquid. In other words, ions in weakly conducting liquids are capable of forming more or less stable structures whose viscoelastic properties are different from those of an uncharged liquid. One method of studying this effect is to investigate the velocity dispersion of ultrasound on charged supermolecular formations. The results of theoretical and experimental investigations of acoustic dispersion in liquid dielectrics subjected to prebreakdown electric fields are presented. A model problem of sound propagation in a liquid in which supermolecular structures have formed around elementary charge carriers is studied theoretically. Approximate formulas describing the dispersion of the acoustic phase velocity as a function of the electric field parameters and the electrophysical parameters of the liquid are obtained. The frequency dependence of the sound velocity is of a resonance character, the resonance frequency being determined by the electric charge density and the mass of the charged supermolecular structures. The experiments showed that the space charge affects the velocity of acoustic waves in liquid dielectrics. Zh. Tekh. Fiz. 67, 105–111 (October 1997)  相似文献   

18.
Nonlinear stimulation of the vorticity mode caused by losses in the momentum of sound in a chemically reacting gas is considered. The instantaneous dynamic equation for the vorticity mode is derived. It includes a quadratic nonlinear acoustic source, which reflects the fact that the reason for the interaction between sound and the vorticity mode is nonlinear. Both periodic and aperiodic sound may be considered as the origin of the vorticity flow. The equation governing the mean flow (the acoustic streaming) in the field of periodic sound is also derived. In the non-equilibrium regime of a chemical reaction, there may exist streaming vortices whose direction of rotation is opposite to that of the vortices in the standard thermoviscous flows. For periodic sound, this is illustrated by an example. The theory and the example describe both equilibrium and non-equilibrium chemical reactions.  相似文献   

19.
The ears of fishes are remarkable sensors for the small acoustic disturbances associated with underwater sound. For example, each ear of the Atlantic cod (Gadus morhua) has three dense bony bodies (otoliths) surrounded by fluid and tissue, and detects sounds at frequencies from 30 to 500 Hz. Atlantic cod have also been shown to localize sounds. However, how their ears perform these functions is not fully understood. Steady streaming, or time-independent, flows near a 350% scale model Atlantic cod otolith immersed in a viscous fluid were studied to determine if these fluid flows contain acoustically relevant information that could be detected by the ear's sensory hair cells. The otolith was oscillated sinusoidally at various orientations at frequencies of 8-24 Hz, corresponding to an actual frequency range of 280-830 Hz. Phase-locked particle pathline visualizations of the resulting flows give velocity, vorticity, and rate of strain fields over a single plane of this mainly two-dimensional flow. Although the streaming flows contain acoustically relevant information, the displacements due to these flows are likely too small to explain Atlantic cod hearing abilities near threshold. The results, however, may suggest a possible mechanism for detection of ultrasound in some fish species.  相似文献   

20.
The idea of similarity between acoustic fields in a moving fluid and in a certain "effective" quiescent medium, first put forward by Lord Rayleigh, proved very helpful in understanding and modeling sound propagation in an atmosphere with winds and in an ocean with currents, as well as in other applications involving flows with small velocity compared to sound speed. Known as effective sound speed approximation, the idea is routinely utilized in the contexts of the ray theory, normal mode representation of the sound field, and the parabolic approximation. Despite the wide use of the concept of effective sound speed in acoustics of moving media, no theoretical justification of Rayleigh's idea was published that would be independent of the chosen representation of the sound field and uniformly apply to distinct propagation regimes. In this paper, we present such a justification by reducing boundary conditions and a wave equation governing sound fields in the inhomogeneous moving fluid with a slow flow to boundary conditions and a wave equation in a quiescent fluid with effective sound speed and density. The derivation provides insight into validity conditions of the concept of effective quiescent fluid. Introduction of effective density in conjunction with effective sound speed is essential to ensure accurate reproduction of acoustic pressure amplitude in the effective medium. Effective parameters depend on sound speed, flow velocity, and density of the moving fluid as well as on sound propagation direction. Conditions are discussed under which the dependence on the propagation direction can be avoided or relaxed.  相似文献   

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