Wellbore drift flow relation suitable for full flow pattern domain and full dip range

Aiming at the simulation of multi-phase flow in the wellbore during the processes of gas kick and well killing of complex-structure wells(e.g.,directional wells,extended reach wells,etc.),a database including 3561 groups of experimental data from 32 different data sources is established.Considering the effects of fluid viscosity,pipe size,interfacial tension,fluid density,pipe inclination and other factors on multi-phase flow parameters,a new gas-liquid two-phase drift flow relation suitable for the full flow pattern and full dip range is established.The distribution coefficient and gas drift velocity models with a pipe inclination range of-90°–90°are established by means of theoretical analysis and data-driven.Compared with three existing models,the proposed models have the highest prediction accuracy and most stable performance.Using a well killing case with the backpressure method in the field,the applicability of the proposed model under the flow conditions with a pipe inclination range of-90°–80°is verified.The errors of the calculated shut in casing pressure,initial back casing pressure and casing pressure when adjusting the displacement are 2.58%,3.43%,5.35%,respectively.The calculated results of the model are in good agreement with the field backpressure data.

Exact solutions to drift-flux multiphase flow models through Lie group symmetry analysis

In the present paper, Lie group symmetry method is used to obtain some exact solutions for a hyperbolic system of partial differential equations （PDEs）, which governs an isothermal no-slip drift-flux model for multiphase flow problem. Those sym- metries are used for the governing system of equations to obtain infinitesimal transforma- tions, which consequently reduces the governing system of PDEs to a system of ODEs. Further, the solutions of the system of ODEs which in turn produces some exact solutions for the PDEs are presented. Finally, the evolutionary behavior of weak discontinuity is discussed.

Zonal Flows Driven by Small-Scale Drift-Alfven Modes

Generation of zonal flows by small-scale drift-Alfven modes is investigated by adopting the approach of parametric instability with the electron polarization drift included. The zonal mode can be excited by primary modes propagating at both electron and ion diamagnetic drift directions in contrast to the assertion in previous studies that only primary modes propagating in the ion diamagnetic drift directions can drive zonal instabilities. Generally, the growth rate of the driven zonal mode is in the same order as that in previous study. However, different from the previous work, the growth rate is no longer proportional to the difference between the diamagnetic drift frequencies of electrons and ions.

交通流数据的概念漂移探析

概念漂移在很大程度上影响着交通流预测的结果,当数据分布或属性发生了变化,而模型的参数和结构没有及时调整时,模型预测结果的准确性就会大幅度下降,甚至完全失效。研究交通流数据及特点,概念漂移及检测步骤、检测方法,对交通流数据概念漂移发现和检测模型的建立、后期调整和优化交通流预测模型具有重要意义。

改进的栖息地法求解多种产漂流性卵鱼类生态流量方法研究

为了解决产漂流性卵鱼类产卵场栖息地模拟的多鱼种生态流量求解不足的问题,提出一种通过鱼类产卵场栖息地模拟计算,在耦合多种产漂流性卵鱼类生态需求的基础上进行生态流量及阈值计算的求解方法,包括:①采用模糊逻辑法进行产卵场栖息地模拟;②改进优势度模型,并运用熵权法确定鱼种的生态流量权重,加强鱼类产卵场生态流量结果的适用性;③耦合多种鱼类产卵需求求解生态流量,并基于单、多鱼种最适生态流量求解综合生态流量阈值。方法考虑了多种鱼类产卵期间的生态流量需求,增加了鱼种对河流生态需求指示作用的可靠性,研究成果可为水库生态调度提供理论基础,为河流水资源管理提供必要参考。

基于恒定功率的热式流量计设计与测试

针对热式流量计的温度漂移问题,提出了一种恒定功率模式下的热式流量计结构,并对其数字校准方法进行了研究。与传统热式流量计相比,增加了环境探头,该探头内嵌于流体管道壁。各传感器之间采用隔热措施,利用环境探头和感温探头测量得到的电压信号进行实时数字校准。采用音速喷嘴法燃气表检验装置对流量计进行检测。检测结果显示:流量在0.016~0.25 m^(3)/h范围内误差率小于0.5%,流量在0.25~6 m^(3)/h范围内误差率小于1.0%,温度漂移现象有效改善。

高雷诺数下倒虹吸闸墩绕流水力特性

为研究倒虹吸出口闸墩绕流特性,以南水北调某典型倒虹吸为例,基于Flow3D软件建立倒虹吸模型,根据现场原型实测水位、流速进行模型验证;利用该模型模拟了雷诺数6.17×10^(6)~9.38×10^(6)范围下闸墩绕流特性。结果表明,高雷诺数条件下,随着雷诺数的增加,闸墩绕流造成的液面波动幅度增加,中墩液面波动显著大于边墩;闸墩后的尾涡量持续增加,雷诺数对斯特劳哈尔数影响不大;边侧闸墩受力的非对称性明显,边墩闸室间特征流速偏流比存在先增大再减小的变化规律,偏流效应造成的离心距不断增加。本研究可针对性改善输水工程水流流态。

铁路站场风吹雪分布特征研究

风吹雪现象会影响铁路运输安全,积雪严重时阻断铁路交通。因此该论文基于建立的铁路站场和车辆的多相流仿真计算模型,对有无列车停站和不同股道数对风雪场分布特征的影响进行了分析。研究表明,站内无停车时,迎风侧路基区域的流速较低,而站内顺风向的流速逐渐增加,风速和积雪分布的变化趋势相对平缓;而在站内有停车时,列车上风侧存在一个长约8 m、高为2 m的流场减速区,下风侧存在一个长约5 m、高为0.5 m的流场加速区。列车上风侧近处和下风侧远处的雪量增加,上风侧远处和下风侧近处的雪量减少。同时,站场内的股道数也会影响风雪场分布,增加股道数时,站场内的雪量最小值和平均雪量减小,但雪量最大值较为接近且位置都在列车上风侧;站场内的流场变化是雪量分布差异的根本原因,股道数的增加减缓了站场结构对风吹雪的影响作用。

High-order fully implicit SIMPLE-based model for fully implicit simulation of upward two-phase flow

The drift-flux model has a practical importance in two-phase flow analysis.In this study,a finite volume solution is developed for a transient four-equation drift-flux model through the staggered mesh,leading to the development of a fully implicit discretization method.The main advantage of the fully implicit method is its unconditional stability.Newton's scheme is a popular method of choice for the solution of a nonlinear system of equations arising from fully implicit discretization of field equations.However,the lack of convergence robustness and the construction of Jacobian matrix have created several difficulties for the researchers.In this paper,a fully implicit model is developed based on the SIMPLE algorithm for two-phase flow simulations.The drawbacks of Newton's method are avoided in the developed model.Different limiter functions are considered,and the stabilized method is developed under steady and transient conditions.The results obtained by the numerical modeling are in good agreement with the experimental data.As expected,the results prove that the developed model is not restricted by any stability limit.

Shear Flow Dispersion Under Wave and Current

The longitudinal dispersion of solute in open channel flow with short period progressive waves is investigated. The waves induce second order drift velocity in the direction of propagation and enhance the mixing process in concurrent direction. The 1-D wave-period-averaged dispersion equation is derived and an expression for the wave-current induced longitudinal dispersion coefficient （WCLDC） is propased based on Fiscber＇ s expression （1979） for dispersion in unidirectional flow. The result shows that the effect of waves on dispersion is mainly due to the cross-sectional variation of the drift velocity. Furthermore, to obtain a more practical expression of the WCLDC, the longitudinal dispersion coefficient due to Seo and Cheong （1998） is modified to incluee the effect of drift velocity. Laboratory experiments have been conducted to verify the propased expression. The experimental results, together with dimensional analysis, show that tbe wave effect can be reflected by the ratio between the wave amplitude and wave period. A comparative study between the cases with and without waves demonstrates that the magnitude of the longitudinal dispersion coefficient is increased nnder the presence of waves.

Ammonium Salt Deposition Characteristics in an Air Cooler System Based on the Coupling of Fluid Flow and Heat Transfer Simulation

The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations were performed by using the mixture model, the heating transfer model, and the particles tracking model. The results show that the differences between the temperature and the velocity at each cross section of the first-row and second-row tubes are small. The inertia of the particles plays an important role in the particle’s deposition, and the smaller particles distribute more uniformly in the air cooler. However, for larger particles, they prefer falling from the inner side of the vertical elbow, and preferentially depositing at the inlet header and pipes before saturation. In the heat exchanger tubes, the particle deposition number is larger in the second-row tubes than that in the first-row tubes, and the high-risk tubes mainly concentrate on the middle and right side of the air cooler. The kinetic parameters of the particles are in accordance with the blocking-prone position in many real operating conditions.

Experimental study of gas-water elongated bubble flow during production logging

In order to improve the interpretation of production log data on gas-water elongated bubble （EB） flow in horizontal wells, a multi-phase flow simulation device was set up to conduct a series of measurement experiments using air and tap water as test media, which were measured using a real production logging tool （PLT） string at different deviations and in different mixed flow states. By understanding the characteristics and mechanisms of gas-water EB flow in transparent experimental boreholes during production logging, combined with an analysis of the production log response characteristics and experimental production logging flow pattern maps, a method for flow pattern identification relying on log responses and a drift-flux model were proposed for gas-water EB flow. This model, built upon experimental data of EB flow, reveals physical mechanisms of gas-water EB flow during measurement processing. The coefficients it contains are the specific values under experimental conditions and with the PLT string used in our experiments. These coefficients also reveal the interference with original downhole flow patterns by the PLT string. Due to the representativeness that our simulated flow experiments and PLT string possess, the model coefficients can be applied as empirical values of logging interpretation model parameters directly to real production logging data interpretation, when the measurement circumstances and PLT strings are similar.

THE EFFECT OF LIQUID PHYSICAL PROPERTIES ON DRIFT VELOCITY

Drift velocity is a very important paramcter for predictirg the pool volumetric void fraction. Two-phase system of gas and high viscous liquids pool is encountered in various engineering applications. A review of the literature shows no data for explaining the effect of highly viscous liquids on the drift velocity. This paper’s analysis shows that there is a considerable influence. It is shown that the foaming behaviour of liquids is dependent on the surface properties. For some highly viscous liquids at a given superficial gas velocity, the viscosity changes with time. The effect of "foam" and "time" on drift velocity is clearly elucidated.

Investigation of the Parallel Flow in the Edge Plasma of EAST

The effects of the E × B drift and ballooning-like transport on the edge plasma in EAST tokamak are investigated with a simplified fluid model. The simulation results show that the E × B drift and ballooning-like transport affect the plasma behavior. When the toroidal field is reversed, at the low field side the density is much larger and temperatures （both electron and ion） are lower, and the profiles of the density and temperatures become more symmetric. With the ballooning-like transport considered, the spatial ballooning-like distribution at the low field side is not very important, but the magnitude affects the ratios of the inner/outer particle flux and energy as well as the E × B drift. At the top of the scrape-off layer, the Mach number exceeding 0.3 for the normal toroidal field and approaching 0.2 for the reversed toroidal field in the simulation are obtained when the drift and ballooning-like transport are included in the model.

REVIEW ON MATHEMATICAL ANALYSIS OF SOME TWO-PHASE FLOW MODELS

The two-phase flow models are commonly used in industrial applications, such as nuclear, power, chemical-process, oil-and-gas, cryogenics, bio-medical, micro-technology and so on. This is a survey paper on the study of compressible nonconservative two-fluid model, drift-flux model and viscous liquid-gas two-phase flow model. We give the research developments of these three two-phase flow models, respectively. In the last part, we give some open problems about the above models.

基于漂移流模型的管道一维气液两相流数值仿真与分析

两相流模型受到双曲线性质的影响,因为很难获得雅可比矩阵的简洁解析表达式,从而限制了开发Roe型黎曼求解器。针对管道气液两相流流动现象,利用一维气液两相流漂移流模型,建立了管道一维气液两相流控制方程,采用基于时间的限制器,使用Lax-Wendroff方法求解方程组,并以此开发了数值求解器。以垂直管中油气两相流为模型算例,计算了不同时刻的管中沿管道方向的含气率分布,通过分析比较,文中采用的漂移流一维气液两相流模型和数值算法能够满足管道一维气液两相流流动的工程应用。

下游河道对流量变化响应法的研究理论及进展

为探究当前环境流量的研究进展及发展方向,补充环境流量评估方面的研究方法,概述了国内外环境流量研究进展,应用CiteSpace软件结合中国知网与Web of Science数据库分析环境流量研究方法在21世纪以来的历史热点及主题演变情况。从开发背景、模型模块及应用步骤等方面详细介绍了一种用于环境流量评估的整体法——下游河道对流量变化响应法DRIFT(Downstream Response to Imposed Flow Transformation),结合南非奥卡万戈河以及赞比西河工程案例总结了该方法在环境流量评估及生态系统保护研究方面的应用,为环境流量研究提供新的思路与方法。

换热直管内外流诱导振动频率漂移特性

采用二维圆柱绕流模型,得到换热直管在较大范围雷诺数的横掠外流场作用下的升力和阻力函数,将其作为激励,同时考虑管道在非定常流动中的附加质量,建立了一种改进的内外流固耦合计算模型.计算结果表明:横掠外流带来的附加质量会导致管道固有频率的漂移,雷诺数也会影响外部激励的频率.由于内流雷诺数也会影响管道的固有频率,因此在特定的内外流共同作用下管道可能发生共振.本模型可以预测发生共振时内外流雷诺数的范围,为合理设置内外流的安全运行工况提供理论依据.

基于电阻层析成像技术的弹状流实验研究

在气液两相流研究中,相分布、相速度等流场特征信息对深入了解流动机理、提高模型计算精度有重要意义,但由于气液流动的复杂性与随机性,使得它们的准确测量较为困难。该研究基于快速电阻层析成像技术,首先对垂直向上气液管流中弹状流流型下多种工况的流动结构进行图像数据采集与重建;然后通过互相关算法得到轴向速度场分布,并与漂移流模型进行对比;再对按时序排列的横截面图像序列进行调整得到正确比例的空间三维图像;最后获得段塞长度、频率等特征信息。结果表明,快速电阻层析成像技术可以测得速度场分布、段塞长度、频率等特征信息,可用于优化与这些参数相关的理论模型和经验关系式,有助于提高气液两相流的模型计算精度。

“华龙一号”非能动安全壳热量导出系统程序与STAR-CCM+程序耦合计算方法

为更好地对“华龙一号”(Hua-long pressurized reactor 1000,HPR1000)非能动安全壳热量导出系统(passive containment heat removal system,PCS)周围的流场和浓度场进行分析,针对HPR1000 PCS基于漂移流模型开发了一套一维自然循环瞬态计算程序,并将该系统程序与STAR-CCM+程序开展耦合计算研究。PCS程序读取来自STAR-CCM+程序计算的温度、压力及气体组分参数开展计算,并将PCS传热管温度作为返回值传递给STAR-CCM+程序,通过在PCS传热管壁面附近第一层网格内设置冷凝通量的方法将PCS冷凝量及冷凝对应能量从系统中移除。研究结果表明,采用经过验证的PCS程序和耦合计算方法对PCS空间进行计算分析,可以有效控制空间内的温度和压力,PCS周围形成明显的温度和浓度梯度。本研究建立的PCS程序与STAR-CCM+程序耦合计算方法能够用于后续HPR1000及华龙后续机型的PCS研究。