水平井两相渗流

研究了水平井两相渗流问题.在流线不变的假定下,给出了水驱油饱和度的二维分布和见水时间公式。两相渗流的见水时间比活塞式驱替的时间快 f(s_t)倍,f(s_t)是含水百分数在前沿处的导数值。     

视密度加权的时平均统一二阶矩两相湍流模型

在气粒两相湍流的双流体模型中,颗粒相的视（表观）密度是有脉动的,在时平均的统一二阶矩（USM）模型中出现了和颗粒数密度或视密度脉动有关的项和方程,使模型方程比较复杂。实际上,用LDV或PDPA测量的流体（用小颗粒代表）和颗粒速度都是颗粒数加权平均的结果。因此,在视密度加权平均基础上推导两相湍流模型更为合理。通过推导和封闭了视密度加权平均的统一二阶矩模型（MUSM）方程组,改进了两相速度脉动关联的封闭,并引入了颗粒遇到的气体脉动速度及其输运方程。MUSM模型可以减少所用方程数,节省计算量。视密度加权平均的统一二阶矩两相湍流模型是一种对原有时间平均的统一二阶矩模型和改进和发展。     

油-气两相流管线系统振动分析及减振控制

针对油-气主管线系统的油-气两相流振动问题,建立了管线系统的动力学模型.分析计算油-气两相流在管道内的动力学特性,判断其流型;根据动量定理得到了管线各处受力的时间历程,从而确定管道系统受到的实际动载荷并求出其振动时间历程响应;分析管线系统的模态和影响振动模态的关键因素,采用合理加强原有支撑刚度和在恰当部位增加新支撑等措施,使管道系统的振动得到控制.分析结果与现场实测数据对比,验证了此振动分析方法的有效性.     

垂直下降管中两相流的流型以及液相粘度对流型的影响

对空气－油在垂直下降管中的流型进行了实验研究，采用的管径为２９ｍｍ，油和空气的折算流速分别达到４ｍ／ｓ和２０ｍ／ｓ，并借助于压降脉动分析和目测观察相结合的方法来进行流型的识别。研究表明，油气两相流的流型不同于低粘液体的两相流流动，通过实验研究并结合前人的研究成果，给出了液相粘度对流型转变的影响趋势。     

系统压力对含悬浮颗粒油液的影响研究

油液在运行过程中不可避免地会产生颗粒物,影响油液的正常使用,甚至出现设备故障,因而分析含悬浮颗粒油液的动态特征,掌握在不同压力变化条件下油液及颗粒物的变化规律具有重要意义。利用两相流体理论建立了含悬浮颗粒油液的悬浮流动力学模型,通过特征线法进行了数值求解,将数值结果与实验数据比较,具有较好的一致性;根据所建模型,分析了不同系统压力条件下悬浮流中各相的脉动规律。结果表明,流场中各相参数的脉动幅值随着系统压力的增加而增大;管路始端和终端各相参数的脉动时刻分别位于1/4脉动周期(T)的奇数倍和偶数倍处,管路中段各相参数的脉动时刻则位于T/8的奇数倍处;悬浮颗粒速度会受到油液速度拖曳力作用,其变化趋势与油液速度基本一致,颗粒浓度分布与油液压力的变化趋势完全相反。     

油-水两相湍浮力回流双流体模型

在自然界和工程技术的许多领域,常遇到这样一类物理性质相差悬殊的两相复杂湍流,其特点是流场中包含有回流和因两相间的密度差而产生的浮力,在一定条件下,流场的密度分布会发生突变,使数学模拟和数值计算的难度大大增加。本文把研究精细的油污染预报模型作为基本目标,广泛地涉及了两相湍流精细模拟的理论和方法。用Eulerian坐标系中多流体模型统一描述油和水两相各自的运动,并分别对油和水本身的湍流输运规律以及相间相互作用规律进行模拟,建立了油-水两相湍浮力回流双流体模型及相应的数值计算方法。选定了包含有浮力和回流的两相复杂湍流作为模拟对象,对模型进行了数值验证,并与实测资料作了对比。然后,对油-水两相湍流进行了预报。结果表明,模型的模拟效果非常满意。     

基于颗粒湍流和颗粒碰撞相互作用规律的湍流模型的研究

颗粒湍流和颗粒碰撞的相互作用规律是两相流动中的核心问题。用颗粒湍流模型和颗粒碰撞的动力论模型叠加的方法在研究两相湍流流动方面取得了一定的成效,但是还有待改进。本文基于颗粒湍流形成大尺度脉动和颗粒间碰撞引起小尺度脉动的概念,从双流体模型出发,建立了两相流动的双尺度kp-pε两相湍流模型。利用该模型对下行床和突扩室内的气固...     

布置方式对U型管不稳定性的影响

从实验和理论两方面研究了不同布置方式对加热Ｕ型管不稳定性的影响。实验在氟利昂－１１３试验台上进行，研究了不同布置Ｕ型管在三种压力工况，六种加热工况及各种流量下的流动不稳定性。理论研究得出了系统稳定性的判据，比较了不同布置方式Ｕ型管的脉动起始边界；并对实际工业现场的Ｕ型管布置方式进行了模拟数值计算，比较了在较高系统压力下不同布置方式Ｕ型管的脉动起始边界     

锡黄铜在3.5%NaCl中的液固两相流冲蚀机理研究

利用旋转式冲蚀磨损试验机,对锡黄铜在3.5%NaCl溶液中进行液固两相流冲蚀磨损试验,利用扫描电镜详细分析了不同条件下锡黄铜表面的微观形貌、失效规律及微观破坏机理.结果表明:锡黄铜在失重的不同阶段对应不同的磨损机制,在不同外界条件下其破坏机制也不尽相同.锡黄铜在阴极保护即无腐蚀影响下,试样发生严重冲蚀前存在门槛速度,冲蚀形貌主要以犁削和铲削为主同时兼有切片.当冲蚀速率增加,冲蚀切削形貌减少,而冲蚀时间的增加将导致冲蚀率首先增加后减小并趋于平衡;在无阴极保护作用下,试样表面出现腐蚀凹坑,冲蚀率大幅度增加,随着冲蚀速率的增加失重率增加,但随冲蚀时间增加,冲蚀率减小.     

航空发动机轴承腔润滑的气液两相均匀流研究

基于轴承腔中润滑油的两相均匀流动模型,采用湍流模式和有限差分数值方法计算轴承腔内三维定常N-S方程,对腔内润滑油的气液两相均匀流动特性进行研究,以获得气液两相均匀流条件下润滑油流场、压力场和速度场在轴承腔内的分布情况,分析转子转速、含气率和润滑油进口速度对润滑油出口压力以及润滑油与壁面之间剪切力的影响,同时对单相流和两相均匀流润滑性能差异进行比较.结果表明,转子转速、含气率和润滑油进口速度对润滑油出口压力和腔内壁面与润滑油间的平均剪切力具有不同影响,而采用2种流动模型计算出的轴承腔润滑油出口压力的差异较大,同时支持了开展航空发动机轴承腔润滑两相流动分析的必要性.     

Water-lubricated transport of high-viscosity oil in horizontal pipes: The water holdup and pressure gradient

This paper has investigated the water holdup and the pressure gradient of water-lubricated transport of high-viscosity oil flow in horizontal pipes. Experimental results on the water holdup and the pressure gradient of water-lubricated high-viscosity oil two-phase flow in a horizontal 1 in. pipe were discussed. Models for the prediction of the water holdup and/or the pressure gradient of core flow or water-lubricated flow were reviewed and evaluated. It was found that the water holdup of the water-lubricated flow is not only closely related to the input water volume fraction but also the degree of the oil phase eccentricity which is attributed to the oil phase Froude number. This can explain the inconsistency of the experimental results with regard to the relationship between the water holdup and the input water volume fraction in the literature. The applicability of the existing empirical or mechanistic models of water-lubricated high-viscosity oil flow were discussed and demonstrated. A modified correlation to the water holdup correlation of Arney et al. (1993) which was shown to be exclusively applicable for concentric core flow was introduced for stable water-lubricated flow, including both concentric and eccentric core flows. This correlation was evaluated and a fair applicability was shown. The accuracy of different models for the prediction of the pressure gradient of water-lubricated transport of high-viscosity oil was demonstrated to be not high in general. This is closely associated with the difficulty in accurately accounting for the influence of oil fouling on the pressure gradient.     

Investigations of phase inversion and frictional pressure gradients in upward and downward oil–water flow in vertical pipes

The present study has attempted to investigate phase inversion and frictional pressure gradients during simultaneous vertical flow of oil and water two-phase through upward and downward pipes. The liquids selected were white oil (44 mPa s viscosity and 860 kg/m³ density) and water. The measurements were made for phase velocities varying from 0 to 1.24 m/s for water and from 0 to 1.87 m/s for oil, respectively. Experiments were carried either by keeping the mixture velocity constant and increasing the dispersed phase fraction or by keeping the continuous phase superficial velocity constant and increasing the dispersed phase superficial velocity. From the experimental results, it is shown that the frictional pressure gradient reaches to its lower value at the phase inversion point in this work. The points of phase inversion are always close to an input oil fraction of 0.8 for upward flow and of 0.75 for downward flow, respectively. A few models published in the literature are used to predict the phase inversion point and to compare the results with available experimental data. Suitable methods are suggested to predict the critical oil holdup at phase inversion based on the different viscosity ratio ranges. Furthermore, the frictional pressure gradient is analyzed with several suitable theoretical models according to the existing flow patterns. The analysis reveals that both the theoretical curves and the experimental data exhibit the same trend and the overall agreement of predicted values with experimental data is good, especially for a high oil fraction.     

Prediction of the drag reduction effect of pulsating pipe flow based on machine learning

Prediction of drag reduction effect caused by pulsating pipe flows is examined using machine learning. First, a large set of flow field data is obtained experimentally by measuring turbulent pipe flows with various pulsation patterns. Consequently, more than 7000 waveforms are applied, obtaining a maximum drag reduction rate and maximum energy saving rate of 38.6% and 31.4%, respectively. The results indicate that the pulsating flow effect can be characterized by the pulsation period and pressure gradient during acceleration and deceleration. Subsequently, two machine learning models are tested to predict the drag reduction rate. The results confirm that the machine learning model developed for predicting the time variation of the flow velocity and differential pressure with respect to the pump voltage can accurately predict the nonlinearity of pressure gradients. Therefore, using this model, the drag reduction effect can be estimated with high accuracy.     

喷管对水下爆轰气泡形态和压力特征影响的实验研究

针对具有不同类型喷管的爆轰管在水下爆轰中形成的燃气射流问题，搭建了爆轰实验平台，研究了单次爆轰过程中尾部喷管对水下气泡形态与压力特征的影响。采用数字粒子图像测速技术对高速摄影机拍摄得到的气泡脉动图片进行流场可视化分析，得到各喷管工况下的气泡速度场。为了确认爆轰管内是否形成稳定爆轰波，并观察爆轰波在气液两相界面上的透反射特性，爆轰管尾部安装有2个动态压力传感器，同时在距离喷管一定距离处设置一个水下爆炸传感器，以监测水中传播的压力波。结果表明：扩张喷管工况下的气泡脉动过程与直喷管工况基本一致，但扩张喷管提高了燃气射流速度，气泡膨胀体积更大；因为燃气射流的持续性，收敛喷管工况下的气泡脉动过程具有明显差异，气泡膨胀体积较小，但气泡二次脉动时长相较于一次脉动时长衰减更小；扩张喷管提高了气泡脉动强度，扩张喷管工况下的气泡脉动压力与透射冲击波压力远大于直喷管工况下的气泡脉动压力与透射冲击波压力；收敛喷管工况下的气泡脉动压力与透射冲击波压力都较小，但收敛喷管燃气射流的持续性减缓了气泡脉动压力的衰减速度。相比于直喷管，扩张喷管工况下的气泡脉动时间、气泡脉动压力与透射冲击波压力都更大。收敛喷管工况下的气泡...     

Experimental investigations of flow field and heat transfer characteristics due to periodically pulsating impinging air jets

The paper concentrates on increasing convective heat transfer due to periodically pulsating impinging air jets. A maximum enhancement rate of cooling effectiveness up to 20% could be detected at an excitation Strouhal number of Sr = 0.82 when using a high pulsation magnitude. Reductions up to 5% occured at low Strouhal numbers with coincident high pulsation magnitudes as well. The thermal results were completed with phase-locked flow field investigations by means of PIV and surface visualizations using the oil film method.     

Flow of oil–water emulsions through a constricted capillary

The flow of oil-in-water emulsions through quartz micro-capillary tubes was analyzed experimentally. The capillaries were used as models of connecting pore-throats between adjacent pore body pairs in high-permeability media. Pressure drop between the inlet and outlet ends of the capillary was recorded as a function of time, for several values of the volumetric flow rate. Several distinct emulsions were prepared using synthetic oils in deionized water, stabilized by a surfactant (Triton X-100). Two oils of different viscosity values were used to prepare the emulsions, while two distinct drop size distributions were obtained by varying the mixing procedure. The average oil drop size varied from smaller to larger than the neck radius. The results are presented in terms of the extra-pressure drop due to the presence of the dispersed phase, i.e. the difference between the measured pressure drop and the one necessary to drive the continuous phase alone at the same flow rate. For emulsions with drops smaller than the capillary throat diameter, the extra-pressure drop does not vary with capillary number and it is a function of the viscosity ratio, dispersed phase concentration and drop size distribution. For emulsions with drops larger than the constriction, the large oil drops may partially block the capillary, leading to a high extra pressure difference at low capillary numbers. Changes in the local fluid mobility by means of pore-throat blockage may help to explain the additional oil recovery observed in laboratory experiments and the sparse data on field trials.     

Calculation of principal characteristics of turbulent streams in a state of structural equilibrium

A review of articles on the study of turbulent streams having transverse displacement, in which a turbulent energy balance equation is used, is contained in [1]. Levin [2] proposed a certain development of Rotta's method [3] making it possible to determine the characteristics of the average flow and the radial distribution of pulsation magnitudes. However, in this article the scale of the turbulence (the quantityl) was given as an empirical function of the coordinates. At the same time it is clear that the distribution of the turbulence scale depends on the conditions of the problem. A special differential equation proposed in [4,5] describing the variation in time and space of the quantityl has the drawback that in deriving this equation it is necessary to invoke additional hypotheses which are difficult to test experimentally. In the present article, along with the velocity of the average flow, the pressure, and the pulsation magnitudes, the scale of the turbulence is considered as an important characteristic of the stream, determined by the reference system which consists of the Reynolds equations, continuity equations, and equations for the component of the Reynolds stress tensor. Rotta's approximate semiempirical relations and an experimental relation for the single-point correlation coefficient between the turbulent pulsations in velocity are used for closure of the system obtained. An approximate calculation is given for the principal average and pulsation characteristics of the flow for the region of the stream where the turbulence is in a state of structural equilibrium [6]. A comparison of the calculated and experimental data is presented.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 95–99, January–February, 1973.     

Pressure pulsations on an obstacle in a jet

At the present time, much attention is devoted to auto-oscillations that arise from the interaction between a supersonic underexpanded jet and an obstacle that it encounters at right angles [1, 2]. There are far fewer data on the pressure pulsations on an obstacle in the absence of auto-oscillations [3–6]. However, in many cases the highest total levels of the pressure pulsations are observed when the barrier is situated at fairly large distances from the nozzle opening and the pressure pulsations have a random nature. We have investigated the pressure pulsations on a plate normal to a supersonic strongly underexpanded jet. The pulsation characteristics were measured for an arrangement of the obstacle when auto-oscillations are absent. We have established dependences that generalize the results of measurement of the pulsation characteristics at both subsonic and supersonic velocities on the jet axis directly in front of the obstacle. We have also investigated the correlation between the pressure pulsations on the plate and external acoustic noise. We have obtained the dependence of the level of the acoustic noise on the value of the maximal pressure pulsations on the plate.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 163–167, January–February, 1980.