An analytic solution of dense two-phase flow in a vertical pipeline

According to a mathematical model for dense two-phase flows presented in theprevious paper,a dense two-phase flow in a vertical pipeline is analytically solved,and theanalytic expressions of velocity of each continuous phase and dispersed phase arerespectively derived The results show that when the drag force between two phases dependslinearly on their relative velocity,the relative velocity profile in the pipeline coincides withDarcy’s law except for the thin layer region near the pipeline wall,and that the theoreticalassumptions in the dense two-phase flow theory mentioned are reasonable.     

Transients in a two-phase medium flowing in a pipeline

The paper examines a water hammer in an elastic pipeline through which a liquid containing solid particles flows. The effect of the particle phase on the pressure jump in the liquid-particle mixture is studied. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 10, pp. 80–86, October, 1999.     

Transportation characteristics of gas-solid two-phase flow in a long-distance pipeline

In this study,experiments on fly ash conveying were carried out with a home-made long-distance positive-pressure pneumatic conveying system equipped with a high performance electrical capacitance tomography system to observe the transient characteristics of gas-solid two-phase flow.The experimental results indicated that sol ids throughput increased with increasing solids-gas ratio when the conveying pipeline was not plugged.Moreover,the optimum operating state was determined for the 1000 m long conveying pipeline with a throttle plate of 26 orifices.At this state the solids throughput was about 12.97 t/h.Additionally,the transportation pattern of fly ash gradually changed from sparse-dense flow to partial and plug flows with increasing conveying distance because of the conveying pressure loss.These experimental results provide important reference data for the development of pneumatic conveying technology.     

清管载荷作用下输气管道安全落差研究

山地天然气管道局部落差和坡度大,在清管过程中易在清管器冲击载荷作用下发生屈曲和应力超限.基于有限元方法研究了考虑管-土耦合作用的大落差管段清管过程非线性动力学特征,分析了清管器运行速度、管道坡度、清管器-管内壁间摩擦系数对管道受力和位移的影响,得到了不同坡度、摩擦系数条件下极限清管运行速度和最大高程差.结果表明:清管器...     

Transportation characteristics of gas–solid two-phase flow in a long-distance pipeline

In this study, experiments on fly ash conveying were carried out with a home-made long-distance positive-pressure pneumatic conveying system equipped with a high performance electrical capacitance tomography system to observe the transient characteristics of gas–solid two-phase flow. The experimental results indicated that solids throughput increased with increasing solids–gas ratio when the conveying pipeline was not plugged. Moreover, the optimum operating state was determined for the 1000 m long conveying pipeline with a throttle plate of 26 orifices. At this state the solids throughput was about 12.97 t/h. Additionally, the transportation pattern of fly ash gradually changed from sparse–dense flow to partial and plug flows with increasing conveying distance because of the conveying pressure loss. These experimental results provide important reference data for the development of pneumatic conveying technology.     

组合导航技术在油气管道测绘系统中的应用

针对长输油气管线必须进行轨迹绘制和探伤定位的问题,设计了惯性管道测绘系统。系统核心部件为捷联惯导系统,辅助信号有里程计和定距离磁标信号,是一种全自主的导航系统。在系统算法设计中,通过建立捷联惯导与航位推算组合导航系统误差模型,利用改进的卡尔曼滤波器估计系统姿态、航向角误差和里程计标度因数误差。该系统数据处理具有非实时性的特点,因此设计了后向卡尔曼滤波器进行数据平滑。系统跑车试验证明该滤波算法能够有效的提高系统的定位精度,系统具有高精度、高可靠的特点,满足实际工程需要。     

On the hyperbolicity of one-dimensional models for transient two-phase flow in a pipeline

Characteristic properties of one-dimensionalmodels of transient gas-liquid two-phase flows in long pipelines are investigated. The methods for studying the hyperbolicity of the systems of equations of multi-fluid and drift-fluxmodels are developed. On the basis of analytical and numerical studies, the limits of the hyperbolicity domains in the space of governing dimensionless parameters are found, and the impact of the closure relations on the characteristic properties of the models is analyzed. The methods of ensuring the global unconditional hyperbolicity are proposed. Explicit formulas for the eigenvelocities of the system of the drift-flux model equations are obtained and the conclusions about their sign-definiteness are drawn.     

Simulation and transport phenomena of a ternary two-phase flow

A chemical flood model for a three-component (petroleum, water, injected chemical) two-phase (aqueous, oleic) system is presented. It is ruled by a system of nonlinear partial differential equations: the continuity equation for the transport of each of its components and Darcy's equation for the two-phase flow. The transport mechanisms considered are ultralow interfacial tension, capillary pressure, dispersion, adsorption, and partition of the components between the fluid phases (including solubilization and swelling).The mathematical model is numerically solved in the one-dimensional case by finite differences using an explicit and direct iterative procedure for the discretization of the conservation equations. Numerical results are compared with Yortsos and Fokas' exact solution for the linear waterflood case including capillary pressure effects and with Larson's model for surfactant flooding. The effects of the above-mentioned transport mechanisms on concentration profiles and on oil recovery are also analyzed.     

Non-isothermal two-phase flow with a diffuse-interface model

In this paper a previously developed diffuse-interface method for numerical simulation of isothermal two-phase flow of a single component is extended to non-isothermal situations. Since no artificial spreading of the interface is applied and no local grid refinement is used, the fluid should be close to its critical point to have an interfacial thickness not too small compared to the size of the computational domain. The use of a non-monotonic Van der Waals equation of state in the vicinity of the critical point causes elliptical behavior of the system of governing equations in part of the phase diagram. A linear stability analysis shows that the rate at which small perturbations grow is reduced with respect to the isothermal case. By adopting a Total Variation Diminishing time-integration scheme, a stable solution method is obtained. One- and two-dimensional simulations are performed to test the applicability and accuracy of the method. The dynamics of the head-on collision of two drops is studied for various combinations of Weber and Prandtl numbers, with particular attention to the effect of the temperature distribution.     

An improved model for two-phase flow through beds of coarse particles

A one-dimensional model for two-phase flow in packed particle beds is presented. Compared with earlier models, the improved model takes into account the effect of interfacial drag forces between liquid and gas, which are of considerable influence in beds of coarse particles. The model is based on the momentum equations for separated flow, which are closed by empirical relations for the wall shear stress and the interfacial drag. The model is applied to the situation of a one-component two-phase flow in an internally heated bed of uniform spherical particles. An increased dryout heat flux is predicted if liquid enters the bed through the bottom.     

Accurate computation of convective transport in transient two-phase flow

The Van Leer method for the computation of convective fluxes is extended to two-phase flow. By preventing spurious undershoots and overshoots, the scheme preserves physical realism while maintaining high-order accuracy. This is particulary important for two-phase flows, since phase exchange terms are typically a function of volume fraction products and numerical diffusion can incorrectly mix the two phases. The scheme described here is constructed to guarantee that the sum of the volume fractions is always unity and that the volume fractions are always greater than or equal to zero. Various test problems are computed to demonstrate the accuracy of the method and to show how the scheme might be incorporated in existing computational methods. In addition to multiphase flow applications, setting equal phase velocities results in a volume marker scheme that is well suited to single-phase interface tracking problems.     

An investigation of hydraulic fracturing. Part II: two-phase flow model

In the previous work presented in Part I (Theoret. Appl. Fracture Mech. 18, 89–102 (1993)), hydraulic fracture in an infinitely large saturated porous medium is analyzed under an assumption of one-phase flow in the medium. The investigation is extended in this paper to the case of a two phase saturated immiscible flow of oil and water in the porous medium. The medium is initially saturated with oil. Flow in the medium is induced by diffusion of water injected into the fracture. The quasi-static growth of the fracture for a prescribed injection rate is analyzed based on the assumptions that the pressure in the fracture is uniform and that the permeating flow in the medium is unidirectional. The constant fracture toughness criterion for plane strain deformation is employed and the effect of capillary pressure is neglected. Empirical formulas are used for the permeabilities of the oil and water phases. It is seen that the distributions of water saturation and pore pressure in the medium are governed by two nonlinear partial differential equations. Numerical solutions are obtained by a finite difference scheme with iterations. It is found that the injected water is restricted within a layer near the surface of the fracture whose thickness is small compared with the length of the fracture. Thus the flow in the medium is governed essentially by the oil phase. To compare our problem with the corresponding problem of one-phase flow, we find that the difference in crack growth in these two problems is small for the ration of kinematic viscosities of the oil and water phases within the practical range. Hence our study confirms the validity of the one phase flow assumption used in the previous work for prediction of hydraulic fracture growth.     

Extension of a multi-surface plasticity model to two-phase materials

The work reported in this paper is part of the ongoing research on the development of suitable elastic–plastic constitutive models for multiphase materials. This paper is concerned with the application of an elastic–plastic constitutive model based on the Mróz-multi-surface kinematic hardening rule to particulate metal matrix composites (PMMCs). Details of the Mróz-based elastic–plastic constitutive model for PMMCs and its explicit implementation are presented to enhance the applicability of the model for a stress controlled simulation. Comparison between numerical predictions and experimental results is also presented for uniaxial loading and biaxial proportional and non-proportional loading paths. For the load paths tested, reasonable agreement is observed between the numerical and the experimental results.     

Estimation of solid concentration in solid-liquid two-phase flow in horizontal pipeline using inverse-problem approach

In this study,an inverse-problem method was applied to estimate the solid concentration in a solid-liquid two-phase flow.An algebraic slip mixture model was int...     

Oil mist transport process in a long pipeline on turbulent flow transition region

Internal gas velocity fluctuations and their effects on the mist diffusion process were examined in a long horizontal pipe to understand oil mist transportation, particularly in the laminar-to-turbulent flow transition region. Three hot-wire anemometers and aerosol concentration monitors were used to deduce these effects as the two-phase mist flow gradually developed in the stream-wise direction. We found significant axial mist diffusion at Reynolds numbers (Re) < 1000 because of passive scalar transport by Poiseuille flow. However, this diffusion was restricted by the non-zero inertia of the mist at a Stokes number, O(10⁻⁵), relying on the Brownian motion of the mist. At Re > 2400, a sharp mist waveform was maintained by a turbulent flow with active radial mixing. New data were obtained within the range of 1000 < Re < 2400, which cannot be explained by interpolation between the above-mentioned two states. The mist concentration displays multiple temporal peaks at Re < 2000 owing to perturbations of localized turbulence as well as radial anisotropy as being conveyed more than 2000-diameters in distance. This behavior is caused by intermittent disturbances induced by the pipe wall roughness, which sharply distorts the wall-aligned laminar mist layer left by parabolic axial stretching of local laminar flow.     

Chemical potential tensor for a two-phase continuous medium model

Relations for jumps of thermodynamic variables with allowance for inertial terms are derived under conditions of thermal equilibrium and in the absence of dissipation on the interphase surface. The notion of the chemical potential tensor is generalized for this case within the framework of the elastic continuous medium model. A thermodynamically well-posed definition of the chemical potential tensor is proposed for a class of two-phase models of deformable solids. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 12–22, May–June, 2005.