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由空压机提供的气体通过—排微小直径的喷嘴进入静止水体,形成水气两相流流场。在单相PIV和PTV技术的基础上,研究稀疏气液两相流情况下气泡的速度场分布。PIV算法采用快速傅立叶互相关分析法,而PTV算法需要获得每幅图像中每个气泡的形心,根据连续图像中的粒子对,计算速度。用PIV和PTV两种算法处理求出气泡的速度并对两种方法进行比较,其最终研究成果可应用于流体及多相流的流量测技术,提高我们进行低密度气液两相流相关研究的测量水平。同时为水气两相流的数值分析和理论研究提供流场测试的数据。 相似文献
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基于爆轰数值模拟计算,分析了CL-20混合炸药爆轰反应的特征,设计了炸药与窗口的界面粒子速度测量实验装置;采用激光干涉法,测量了C-1炸药(CL-20/粘合剂/94/6)与窗口的界面粒子速度; 运用先求导、再分段拟合的方法,对界面粒子速度随时间的变化曲线进行了数据处理,确定了炸药爆轰CJ点对应的时间位置;根据CJ点对应的粒子速度,计算获得了炸药的爆轰反应区宽度和CJ爆轰压力。结果显示:密度为1.943 g/cm3的C-1炸药的爆轰反应时间为38 ns,CJ压力为34.2 GPa。 相似文献
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利用光学多普勒效应和外差方法搭建了一台光纤位移干涉仪。装置采用光通信行业中已经发展成熟的器件,主要由带尾纤的半导体激光器、三端口环形器、光纤探头、宽带探测器以及宽带高采样率示波器等构成。整个装置结构简单,价格便宜,采用了信号光和参考光同轴结构,实现了任意反射面的速度测量,克服了偏振模式色散的影响,能够实现长量程测量,量程达到20 mm。利用该装置进行了爆轰加载下飞片速度测量,测量最高速度达到1 300 m/s,工作距离达到20 mm,同时利用VISAR对飞片速度进行了对比测量,结果表明用两种不同方法所测得的速度曲线吻合很好。 相似文献
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在低密度风洞试验流场中,加入少量纳米粒子,可以增强瑞利散射测速试验的散射光强度.纳米粒子能否适应流场气流速度变化是测量结果准确性的关键.为了研究瑞利散射测速实验中测量到的纳米粒子的速度能否反映流场当地气流速度,采用基于直接模拟蒙特卡罗方法的稀薄两相流双向耦合算法,对低密度风洞流场中纳米粒子在大梯度流场中的跟随性进行了数值研究.仿真了10 nm,50 nm和100 nm TiO2三种尺寸的纳米粒子分别在M6和M12低密度风洞返回舱高超声速绕流流场中的运动特性.仿真结果显示,不同尺寸的纳米粒子在不同的流场稀薄度条件下的跟随性不同,纳米粒子尺寸越小,跟随性越好.在稀薄度较低的M6流场中,10 nm粒子跟随性很好,与瑞利散射测量结果比较接近,粒径50 nm以上的粒子跟随性较差,而在稀薄度较高的M12流场中,10 nm粒子的跟随性也变差,表明通过瑞利散射测量到的纳米粒子速度和流场中气体速度有一定差距,不能准确反映流场当地速度. 相似文献
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圆柱空腔内涡破裂的LDA三维流动测量 总被引:1,自引:0,他引:1
针对旋转圆柱空腔内旋转流场泡状涡破裂现象,设计了实验装置,分析了实验系统中光路设置、折射率补偿、示踪粒子选择等关键问题的处理方法,采用激光多谱勒速度测量技术LDA(LaserDopplerAnemom etry)进行测量,给出了圆柱空腔内子午面上二维速度全场和涡破裂区域的内部三维流动测量结果. 同时给出的数值计算模拟结果和实验测量结果非常吻合. 相似文献
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《力学学报》2017,(6)
在低密度风洞试验流场中,加入少量纳米粒子,可以增强瑞利散射测速试验的散射光强度.纳米粒子能否适应流场气流速度变化是测量结果准确性的关键.为了研究瑞利散射测速实验中测量到的纳米粒子的速度能否反映流场当地气流速度,采用基于直接模拟蒙特卡罗方法的稀薄两相流双向耦合算法,对低密度风洞流场中纳米粒子在大梯度流场中的跟随性进行了数值研究.仿真了10 nm,50 nm和100 nm TiO_2三种尺寸的纳米粒子分别在M6和M12低密度风洞返回舱高超声速绕流流场中的运动特性.仿真结果显示,不同尺寸的纳米粒子在不同的流场稀薄度条件下的跟随性不同,纳米粒子尺寸越小,跟随性越好.在稀薄度较低的M6流场中,10 nm粒子跟随性很好,与瑞利散射测量结果比较接近,粒径50 nm以上的粒子跟随性较差,而在稀薄度较高的M12流场中,10 nm粒子的跟随性也变差,表明通过瑞利散射测量到的纳米粒子速度和流场中气体速度有一定差距,不能准确反映流场当地速度. 相似文献
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本文采用二维激光多普勒测速仪,对水平放置的方形管道中的固体粒子的两维速度进行测量.给出了两维速度、紊流度的分布曲线,并进行了相应的讨论. 相似文献
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两相流显微PIV/PTV系统的开发 总被引:1,自引:0,他引:1
开发了一个能同时测量两相流中两相速度和细颗粒尺寸分布的显微PIV/PTV系统,其硬件系统包括大功率连续激光器、显微镜、高速摄像机;软件系统由改进的球形颗粒图像识别算法、各种图像处理算法和各种先进的PIV/PTV算法组成。其中改进的圆弧识别算法能够进行更准确地进行曲线分割而能对充满噪音并相互重叠的颗粒图像给出较好的识别结果。应用该PIV系统,可以在微秒和微米数量级上捕获细颗粒/气泡图像,并能较准确地同时得到两相速度、颗粒尺寸和浓度分布。对焚香可吸入颗粒物进行了速度和尺寸的同时测量,得到了较满意的结果。 相似文献
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A non-intrusive technique to measure the two-dimensional distribution of line averaged void fraction in a two-phase flow
is discussed. A CCD camera is used to measure the attenuation of light as it passes through a bubbly flow, and this attenuation
is related to the bubble concentration. The technique is appropriate for microbubbly flows where the bubble size is much smaller
than the area imaged by a single pixel and where there are many bubbles attenuating light within each pixel. The measurement
system is calibrated by using a two-dimensional line source microbubble plume as a reference.
Revised: 30 March 2000/Accepted: 14 April 2000 相似文献
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Yixing Li Yuzhang Wang Shilie Weng Yonghong Wang 《Experimental Thermal and Fluid Science》2007,31(8):917-924
Based on previous work, a new temperature measuring system for gas–liquid flow, composed of shielded and unshielded thermocouples, on-line laser detection device for liquid droplets, vacuum pump and wavelet analysis data processor, is developed in this work. The necessity of vacuum pump and the criterion of mesh size selection are also described. Through an application of measuring temperature in saturator, it shows that the system can evaluate the separation of gas–liquid two-phase flow and measure the liquid droplet temperature and the gas temperature effectively in counter-current spraying field. 相似文献
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An instrumentation system was developed to measure two-phase flow velocity and void fraction. The principle of operation of this system was based on the measurement of the electrical impedance of two-phase mixtures. Two-phase velocity is estimated by time-of-flight analysis of signals from two spatially separated sensors. A technique involving measurement of both the capacitance and the conductance of the mixture was used to determine void fraction and correct for the effect of liquid distribution. The string probe instrumentation proved to be durable in air/water and steam/water flows and demonstrated an ability to measure a wide range of flow velocities (1–17 m/s) and void fractions (0.25?0.99+). 相似文献
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Two-phase flow induced-vibration is a major concern for the nuclear industry. This paper provides experimental data on two-phase damping that is crucial to predict vibration effects in steam generators. An original test section consisting of a tube subjected to internal two-phase flow was built. The tube is supported by linear bearings and compression springs allowing it to slide in the direction transverse to the flow. An excitation system provides external sinusoidal force. The frequency and magnitude of the force are controlled through extension springs. Damping is extracted from the frequency response function of the system. It is found that two-phase damping depends on flow pattern and is fairly proportional to volumetric fraction for bubbly flow. Measurements are completed by the processing of high-speed videos which allow to characterize the transverse relative motion of the gas phase with respect to the tube for bubbly flow. It is shown that the bubble drag forces play a significant role in the dissipation mechanism of two-phase damping. 相似文献
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《Journal of Fluids and Structures》2007,23(3):447-462
Two-phase internal flow is present in many piping system components. Although two-phase damping is known to be a significant constituent of the total damping, the energy dissipation mechanisms that govern two-phase damping are not well understood. In this paper, damping of three different clamped–clamped tubes subjected to two-phase air–water internal axial flow is investigated. Experimental data are reported, showing a strong dependence of two-phase damping on void fraction, flow velocity and flow regime. Data-points plotted on two-phase flow pattern maps indicate that damping is greater in a bubbly flow regime. The two-phase damping ratio reaches a maximum value at the highest void fraction before the transition to a churn flow regime. An analytical model that relates the two-phase damping ratio to the interface surface area is proposed. The model is based on rigid spherical bubbles in cubic elementary flow volumes. The analytical results are well correlated with the experiments. 相似文献
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Method of Negative Saturations for Modeling Two-phase Compositional Flow with Oversaturated Zones 总被引:2,自引:1,他引:1
We examine the two-phase flow through porous media of multicomponent partially miscible fluids. The composition of both the
phases is variable in space and time and is assumed to be in local thermodynamic equilibrium. One of the basic problems in
modeling such systems is related to the appearance of single-phase zones occupied by the fluid which is over- (or under-)
saturated, i.e., it is significantly remote from the equilibrium two-phase region. In an oversaturated zone, the two-phase
flow equations degenerate and can no longer be used, which provokes serious numerical problems. We propose to describe the
two-phase and oversaturated single-phase zone by a uniform system of classic two-phase equations while extending the concept
of the phase saturation so that it may be negative and higher than one. Physically this means that we consider the oversaturated
single-phase states as the pseudo two-phase states which are characterized by a negative saturation of the imaginary phase.
Such an extension of the concept of the phase saturation requires the development of some consistence conditions that ensure
the equivalence between the pseudo two-phase equations and the true single-phase flow model in the oversaturated zones. This
method allows using the existing numerical simulators of two-phase flow for modeling single-phase zones by adding a simple
plug-in with no modification of the structure of the simulators. The method is illustrated by several examples of hydrogene-water
flow in a waste radioactive storage and of CO2 injection in an oil reservoir. 相似文献
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《International Journal of Multiphase Flow》1986,12(5):745-758
The local instant formulation of mass, momentum and energy conservations of two-phase flow has been developed. Distribution, an extended notion of a function, has been introduced for this purpose because physical parameters of two-phase flow media change discontinuously at the interface and the Lebesgue measure of an interface is zero. Using a characteristic function of each phase, the physical parameters of two-phase flow have been defined as field quantities. In addition to this, the source terms at the interface are defined in terms of the local instant interfacial area concentration. Based on these field quantities, the local instant field equations of mass, momentum and total energy conservations of two-phase flow have been derived. Modification of these field equations gives the single field representation of the local instant field equations of two-phase flow. Neglecting the interfacial force and energy, this formulation coincides with the field equations of single-phase flow, except in the definition of differentiation. The local instant two-fluid formulation of two-phase flow has also been derived. This formulation consists of six local instant field equations of mass, momentum and total energy conservations of both phases. Interfacial mass, momentum and energy transfer terms appear in these equations, which are expressed in terms of the local instant interfacial area concentration. 相似文献
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The experiment was carried out on the test loop HRTL-5, which simulates the geometry and system design of a 5 MW nuclear
heating reactor. The analysis was based on a one-dimensional two-phase flow drift model with conservation equations for mass,
steam, energy and momentum. Clausius–Clapeyron equation was used for the calculation of flashing front in the riser. A set
of ordinary equations, which describes the behavior of two-phase flow in the natural circulation system, was derived through
integration of the above conservation equations for the subcooled boiling region, bulk boiling region in the heated section
and for the riser. The method of time-domain was used for the calculation. Both static and dynamic results are presented.
System pressure, inlet subcooling and heat flux are varied as input parameters. The results show that subcooled boiling in
the heated section and void flashing in the riser have significant influence on the distribution of the void fraction, mass
flow rate and flow instability of the system, especially at low pressure. The response of mass flow rate, after a small disturbance
in the heat flux is shown, and based on it the instability map of the system is given through experiment and calculation.
There exists three regions in the instability map of the investigated natural circulation system, namely, the stable two-phase
flow region, the unstable bulk and subcooled boiling flow region and the stable subcooled boiling and single phase flow region.
The mechanism of two-phase flow oscillation is interpreted.
Received on 24 January 2000 相似文献
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This paper presents the experimental study and numerical simulation of two-dimensional two-phase flow in horizontal heated
tube bundles. In the experiments, two advanced measuring systems with a single-fibre optical probe and a tri-fibre-optical-probe
were developed to measure respectively the local void fraction and vapor bubble velocities among the heated tube bundles.
In accordance with the internal circulation characteristics of two-phase flow in the tube bundles, a mathematical model of
two-dimensional two-phase low Reynolds number turbulent flow based on the modified drift flux model and the numerical simulation
method to analyze the two-phase flow structures have been developed. The modified drift flux model in which both the acceleration
by gravity and the acceleration of the average volumetric flow are taken into account for the calculation of the drift velocities
enables its application to the analysis of multi-dimensional two-phase flow. In the analysis the distributions of the vapor-phase
velocity, liquid-phase velocity and void fraction were numerically obtained by using the modified drift flux model and conventional
drift flux model respectively and compared with the experimental results. The numerical analysis results by using the modified
drift flux model agree reasonably well with the experimental investigation. It is confirmed that the modified drift flux model
has the capability of correctly simulating the two-dimensional two-phase flow.
Received on 3 September 1998 相似文献