Two-phase Flow Calculations Research Articles

Prediction of Progressive Erosion Characteristics of Centrifugal Pump Blades Based on Dynamic Boundaries

Abstract The conventional method of fixed boundaries for predicting erosion inadequately reflects the erosion characteristics of centrifugal pumps under realistic operating conditions. In this research, we employ the dynamic boundary method, considering the influence of changes in wall morphology due to erosion on the flow field. We utilize the Euler-Lagrange approach and the E/CRC erosion model, incorporating a dynamic boundary geometry reconstruction strategy, to predict the erosion characteristics of the IS80-50-315 single-stage single-suction centrifugal pump. Solid-liquid two-phase flow calculations are conducted on the pump to predict erosion characteristics under varied operating conditions. The results show that the dynamic boundary-based progressive erosion prediction method realistically forecasts the erosion characteristics of the overflow wall and captures the evolution of blade morphology with erosion time. Erosion intensity on the blade suction surface significantly surpasses that on the pressure surface, guided by particle distribution characteristics in the centrifugal pump flow channel. Particle diameter primarily influences the erosion position of centrifugal pump blades; smaller particles induce erosion in the middle region of the blade, while an increase in particle diameter shifts the severe erosion position towards the impeller outlet direction. At a consistent particle diameter, higher particle concentrations correspond to elevated erosion rates in the blade area. We establish a relationship between the blade mass loss rate and erosion time during 2500 hours of pump operation at the design condition, introducing the blade mass loss rate for convenient assessment and prediction of blade damage in the centrifugal pump.

Accelerated calculation of phase-variable for numerical simulation of multiphase flows

In this manuscript, we unveil an innovative acceleration technique for the simulation of multiphase flows, which builds upon the foundation laid by our previously devised multiphase flow solver. The cornerstone of this method lies in augmenting computational efficiency through the selective updating of variables solely within domains characterized by significant gradients of the phase variable. This tactic diminishes the dimensionality of the system of linear equations, thereby hastening the computational process. To pinpoint the regions warranting focused attention, a judicious criterion is indispensable to strike an optimal balance between efficiency and precision. This criterion affords a marked decrement in computational expenditure while preserving the fidelity of the original methodology. Rigorous validations corroborate that this acceleration mechanism can enhance computational efficiency by a minimum of 49.5% in resolving the phase field equation and by at least 70.2% in the computation of pragmatic two-phase flows, without compromising accuracy. Moreover, the efficacy of this acceleration technique is inversely proportional to the rate of interface evolution, becoming increasingly efficient as the interface evolves more slowly.

Experimental research on the transformation of gas-oil two-phase flow pattern in large vertical annulus

Criteria for gas-oil two-phase flow transformation are essential guidelines that are used as auxiliary equations for the calculation of two-phase flows in gas-oil based drilling fluids within wellbores. The currently used flow pattern transformation criteria, which are based on gas-water two-phase flow experiments in circular pipes or small annuli, have limited applicability when calculating the gas-liquid two-phase flows in oil-based drilling fluids. In this study, experiments were carried out on the transformation of gas-oil two-phase flow patterns in a large annulus (φ100 mm × φ60 mm × 12 m) under different viscosities (16–39 mPa s). The flow characteristics of gas-liquid two-phase flows were measured using electrical capacitance volume tomography (ECVT) at different superficial gas-liquid velocities. It was found that as the liquid phase viscosity increased, the slug flow area gradually expanded, and the superficial gas velocity at which the annular mist flow appeared decreased. When the superficial Reynolds number of the liquid phase exceeded the critical value (approximately 135), the slug flow no longer appeared in the wellbore, and the bubble flow was directly transformed into the churn flow. Based on the results of the dimensionless analysis in the experiments, the criteria for flow-type transitions among different flow patterns were established by considering the influence of the liquid-phase viscosity. Both the average relative errors between the predicted and experimental values of the superficial gas velocity during the bubble-slug, bubble-churn, slug-churn, and churn-annular transitions, at the same superficial liquid velocities, were less than 3.5, 4.5, 3, and 7%, respectively.

Analysis and Calculation of Two-Phase Flow in Industrial Pipelines Using Regime Classification

The analysis shows that using regime classification for individual phases, it is possible to obtain a more reliable design scheme for two phase flows. In contrast to the flow structure, the concept of mode is more accessible for calculating an industrial pipeline. In this case, transient processes can be determined and calculated. The analysis shows that in field conditions it is very difficult to determine transition boundaries for flow structures. However, taking into account the structural approach, it is very difficult to determine the boundaries of the flow, and based on the laws of hydrodynamics of a homogeneous liquid and gas, it is possible to determine the transition of one regime to another using the Reynolds number. This technique is based on the theory of the great Russian scientist Academician A.P. Krylov. Let us note that this theory has not yet lost its specialty in the fishing industry. Based on numerous data, a method for calculating the gas-liquid mixture in horizontal pipes is proposed. Based on the laws of homogeneous liquid and gas, an equation for the distribution of speed, flow and pressure loss in a pipeline is obtained. The analysis shows that, based on the laws of homogeneous liquid and gas, it is possible to propose a method for calculating the hydrodynamic parameters of a two-phase flow, such as liquid and gas in a round pipe. This technique is based on the theory of Academician A.P. Krylov, which characterizes the reliability of this technique.

Simulation and Experiment on Elimination for the Bottom-Sitting Adsorption Effect of a Submersible Based on a Submerged Jet

When a submersible is sitting on a seabed, it could lose buoyancy because of the bottom-sitting adsorption effect. In this article, a numerical calculation model and experimental scheme for eliminating the bottom-sitting adsorption effect of under-sea equipment were established. An analysis of the hydrostatic pressure variation on a submersible’s bottom was carried out, and a submerged water jet which was based on the method of soil liquefaction was proposed to solve the problem of reducing hydrostatic pressure. It was shown that a water jet could liquefy soil to restore hydrostatic pressure on the submersible’s bottom, and there was an optimal jet velocity to form the largest liquefied soil thickness. A rectangular pulsed jet was the best way to liquefy soil in terms of efficiency and the liquefaction degree, which can be seen from the calculation of the two-dimensional two-phase flow. Through the calculation of the three-dimensional two-phase flow, it was found that the soil liquefaction developed from the periphery to the center, and a variation in jet liquefaction with the top wall constraint was obtained. Finally, an experiment was carried out to prove that a submerged water jet could eliminate the bottom-sitting adsorption effect of a submersible. The results showed that the submerged jet was an efficient way to liquefy soil, and a submersible could quickly recover hydrostatic pressure on the bottom and refloat up independently.

An efficient two-phase flow calculation method based on grid mergence and dimension transformation

Two-phase flow numerical methods are applied in internal ballistics widely, which has made higher fidelity analysis with minimal cost become an urgent demand. Current methods are based on independent dimension, and there is no definite conversion criterion and data transmission method, which have limited the application of efficient hybrid models applied to calculation. In this paper, we propose a hybrid method by linking a two dimensional (2D) model to a one dimensional (1D) model for two-phase flow. First, 1D and 2D two-phase flow models are established according to the flow field states in different phases. Next, the criterion of conversion between the two models is established, which is a quantitative index to judge the degree of radial effect and axial effect. Finally, dimension transformation in the radial direction and grid mergence in the axial direction are conducted to complete the whole computing model. The simulation results show that the hybrid method is more efficient in the interior ballistic process and maintains the level of trust in classical codes. Compared with the 2D method, the hybrid method significantly improves the computational efficiency by 86.5%. By analyzing the state in the chamber, the accuracy of the conversion criterion is confirmed. This criterion can be used as the transformation criterion of the hybrid model to form the standard multi-dimensional calculation transformation criterion of interior ballistics and may be promising for the rapid simulation of two-phase flow in interior ballistics.

Study on start-up of molten salt fast modular reactor from shutdown based on two-phase flow CFD analysis

In the present study, the effect of helium gas bubbles injected into a molten salt reactor on nuclear characteristics is analyzed. The analysis uses a computational fluid dynamics code and a system code to evaluate the effects of void fraction and core temperature on reactor power, which are affected by changes in fuel pump speed. Because molten salt reactors are equipped with a fission gas removal system such as Xe gas, the core of a molten salt fast reactor is strictly a two-phase flow and the analysis considers the effects of voids. In this system, the Xe gas is removed by injecting helium gas bubbles into the molten fuel salt. When the void fraction of the helium gas increases by 1%, the reactivity of approximately −360 pcm δk/k is introduced. To understand the importance of two-phase flow analysis by the FLUENT code with a user defined function which incorporates the point kinetics model and void effect model, a fuel pump trip at rated reactor power with a void fraction of 0.4% in the core average was analyzed with FLUENT and compared with a conventional analysis that does not consider the effects of voids at all. The results show that the transient behavior cannot be properly evaluated without considering the effects of voids. A comparison of two-phase and single-phase flow calculations using FLUENT is also provided, and a method to evaluate the effects of voids in single-phase flow calculations is also proposed. Analysis using FLUENT under two-phase flow conditions shows that the reactor can increase power by increasing the fuel pump speed. Under single-phase flow assumption, the analysis was performed using RELAP5-3D and showed that the reactor can be started in a similar manner by considering the reactivity associated with changes in the void fraction. It was pointed out that the reactor could be controlled by adjusting the amount of helium injected. It was also noted that voids increase the reactor shutdown margin.

Research on mechanism of enhancing lubrication flow field regulation of high-speed bearing functional cage

With the development of major equipment towards high power density, the bearing speed is getting higher and higher. In the oil-jet lubrication mode, the fluid in the bearing chamber is a two-phase flow of oil and air. Under high-speed operating conditions, the air in the bearing chamber has a significant impact on the lubricating oil flow field and bearing temperature. This article presents a functional cage with wing structures that is designed to regulate the fluid flow field inside the bearing chamber. The numerical simulation model of 2/14 bearing is established. Through computational fluid dynamics (CFD) software, the effects of wing angle, position and length on the regulation of the flow field in the bearing cavity and the axial velocity are analyzed. The results indicate that appropriately increasing the angle and length of the wings, while positioning them closer to the inlet, is an effective way to enhance the regulation of the bearing flow field. The calculation of oil-air two-phase flow and temperature rise test verify that the functional cage bearing has the function of enhancing lubrication and heat dissipation. This research offers both a theoretical basis and practical approaches for developing high-speed bearings that have better lubrication performance and improved heat dissipation.

Drag force modification model for turbulent suspended-load sediment solid–liquid two-phase flow

The calculation accuracy of a solid–liquid two-phase flow numerical simulation is related directly to the reliability of the results obtained. The interphase drag force significantly affects the calculation results of the solid concentration distribution of suspended-load sediment solid–liquid two-phase flow. However, the conventional Wen–Yu drag force model is obtained by adding solid concentration to the standard drag force coefficient curves. The model does not consider the influence of turbulence, which is a comprehensive reflection of particle inertia and liquid turbulence intensity. To improve the calculation accuracy of the Wen–Yu model, the particle inertia and turbulence intensity factors are introduced to express the comprehensive influence of the particle inertia and liquid turbulent intensity on the drag force coefficient for the suspended-load sediment solid–liquid two-phase flow. The turbulence modification function preliminary expression is determined and further modified to improve the calculation accuracy for a particle Reynolds number of less than 100 by combining experimental data and the least square method through experiments and theoretical research. Then, the final expression of the turbulence modification function is proposed to help modify the drag force coefficient of the Wen–Yu model, and finally establish the modified turbulence effect (MTE)-Wen–Yu drag force modification model. The calculations for the suspended-load sediment solid–liquid two-phase flow in the circular tubes show that the solid-phase concentration values calculated by the MTE-Wen–Yu drag force model are considerably closer to the experimental results than those obtained by the Wen–Yu drag force model in the suspended-load sediment solid–liquid two-phase flow calculation for different inlet velocities, inlet solid concentrations, and particle diameters. Hence, the calculation accuracy of the MTE-Wen–Yu model is higher than that of the Wen–Yu drag force model. The calculation precision of the solid-phase concentration distribution calculated using the MTE-Wen–Yu drag force model decreases with the increase in particle diameter owing to the high quality and large inertia of large particles. Therefore, it is more suitable for the numerical simulation of suspended-load sediment solid–liquid two-phase flow with a small particle diameter.

A 1-D/3-D coupling approach for compressible non-equilibrium two-phase flows using the Baer-Nunziato model based on the Finite-Volume framework

An efficient bi-directional 1-D/3-D coupling is here proposed for the computation of compressible two-phase flows with the use of the Baer-Nunziato model. The objective is here to couple the 3-D Baer-Nunziato model with its 1-D counterpart involving spatially varying pipe cross-sections. The present coupling acts at the common interface between three-dimensional and one-dimensional computational domains. The proposed approach is built upon the framework of the Finite-Volume method with, in particular, the exchange of the numerical fluxes coming from the approximation of both conservative and non-conservative terms of the convective part of the Baer-Nunziato model. For this purpose, local Riemann problems at the 1-D/3-D common interface are considered for the computation of the corresponding numerical conservative and non-conservative fluxes. These local Riemann problems are based on the variables associated with the 1-D domain on one side and the variables coming from the 3-D domain on the other side of the interface. The potentially non-null tangential phasic velocity components coming from the 3-D domain at the coupling interface are also considered in the local Riemann problems. In addition, adequate approximations of the non-conservative terms associated with changes of volume fraction as well as changes of cross-section are considered at the 1-D/3-D interface. As a consequence, conservation properties such as the uniform pressure and velocity profiles preservation are ensured by the present 1-D/3-D coupling. The pipe cross-section variations are also taken into account in the present method. What is more, no iterative procedure is required in the proposed approach. Several numerical shock-tubes involving both subsonic and supersonic configurations of the Baer-Nunziato model and pipe cross-section variations are then considered to assess the present 1-D/3-D coupling. The influence of the angle between the 1-D and the 3-D domains at the coupling interface is also studied. Finally, the propagation of a shock-wave in a circular tube with a sudden change in cross-section is simulated using a hybrid 1-D/3-D computation showing the potential of the proposed geometrical multi-scale strategy.

Experimental Investigations and Numerical Studies of Two-Phase Countercurrent Flow Limitation in a Pressurized Water Reactor: A Review

Gas–liquid two-phase countercurrent flow limitation (CCFL) phenomena widely exist in nuclear power plants. In particular, the gas–liquid countercurrent flow limitation phenomena in a pressurized water reactor (PWR) during a loss-of-coolant accident (LOCA) or a small-break loss-of-coolant accident (SBLOCA) play an important role in nuclear reactor safety research. Over several decades, a series of experimental investigations and numerical studies have been carried out to study the CCFL phenomena in a PWR. For the experimental investigations, numerous experiments have been conducted, and different CCFL mechanisms and CCFL characteristics have been obtained in various test facilities simulating different scenarios in a PWR. The CCFL phenomena are affected by many factors, such as geometrical characteristics, liquid flow rates, and fluid properties. For the numerical studies, more and more numerical models were presented and applied to the calculations of two-phase countercurrent flow over the past several decades. It is considered that the computational fluid dynamics (CFD) tools can simulate most of the two-phase flow configurations encountered in nuclear power plants. In this paper, the experimental investigations and the numerical studies on two-phase countercurrent flow limitation in a PWR are comprehensively reviewed. This review provides a further understanding of CCFL in a PWR and gives directions regarding future studies. It is found that relatively fewer investigations using steam–water under high system pressures are performed due to the limitation of the test facilities and test conditions. There are a number of numerical studies on countercurrent two-phase flow in a PWR hot leg geometry, but the simulations in other flow channels were relatively rare. In addition, almost all of the numerical simulations do not include heat and mass transfer. Thus, it is necessary to investigate the effects of heat and mass transfer experimentally and numerically. Furthermore, it is of significance to perform numerical simulations for countercurrent two-phase flow with a fine computational grid and suitable models to predict the formation of small waves and the details in two-phase flow.

Simplified Interfacial Area Modeling in Polydisperse Two-Phase Flows under Explosion Situations

The aim of the present work is to account for polydisperse effects in a two-phase flow with a simple and fast method. Polydisperse two-phase flows arise in numerous applications. Fire sprinkler systems are relevant examples as they release clouds of polydisperse droplets. Another relevant example is the polydisperse two-phase flow created by the detonation of an explosive charge surrounded by a liquid layer. In such a situation, material interfaces are initially present and the created two-phase flow consists of a carrier gas phase and a liquid phase involving many droplets of various sizes. Spherical particles or droplets are usually assumed in two-phase flow computations. When dealing with explosion situations involving both dense and dilute flow regimes, multiple particle diameters can be addressed but at the price of introducing as many additional equations that describe mass, momentum and energy balance of the various particle classes. Consequently, the computation time needed to address numerical resolution increases tremendously. Under explosion situations involving many particle diameters, the method becomes intractable and is usually reduced to a single diameter, which is often insufficient. A simplified approach is developed in the present work to account for a substantial number of particles of different sizes with few extra computational cost. The approach is said to be simplified as a single velocity and a single temperature are considered for all the spherical particles, regardless of their diameters. This type of modeling seems apt for the target explosion situations. The focus is placed on the interfacial area, which is the main parameter involved in the coupling of the two phases. In the present work, Gamma-like continuous probability distributions are considered to address the various sizes of particles. The effects of the size distribution are only summarized in the specific interfacial area, yielding consequently few code modifications while taking into account the polydisperse aspect of the two-phase flow.

Numerical simulation study on the influence of scroll design parameters on helicopter intake system

Based on the numerical simulation theory, this paper establishes the two-phase flow calculation model of sand and air mixture in the sand control vortex tube, and combined with CFD numerical simulation, studies the influence rules of various design parameters of the vortex tube on the total pressure loss and sand dust separation efficiency of the helicopter intake system, optimizes the structural parameters of the vortex tube separator, and puts forward a set of vortex tube design method, it provides a basis for the design optimization of vortex tube.

A Momentum-Conserving Weakly Compressible Navier–Stokes Solver for Simulation of Violent Two-Phase Flows with High Density Ratio

A consistent and conservative formulation for mass and momentum transport is proposed in the context of simulating incompressible two-phase flows by using weakly compressible method. Combined with the evolving pressure projection method to prevent oscillation of the solution induced by the acoustic wave, this solver aims at a robust and accurate computation of violent two-phase flows with a high density ratio, while taking advantage of fully explicit time integration of the weakly compressible Navier–Stokes equations. Coupled with the volume of fluid method for capturing interfaces, the mass and momentum fluxes are evaluated in a consistent manner using the finite volume method. In addition, a special implementation of the pressure projection is devised to avoid velocity-pressure decoupling on a collocated grid. The solver's accuracy and stability are demonstrated through various two-phase flow simulations, including dam break and liquid jet atomization scenarios, emphasizing its momentum-conserving properties.

Numerical Calculation of Solid-Liquid Two-Phase Flow in Open-Design Vortex Pump

This paper mainly based on the CFD platform, numerical simulation of the internal flow field in the open-design vortex pump under different solid particle concentration and particle size is carried out to explore the flow trajectory characteristics of solid particles in the impeller channel and the lateral cavity, as well as the distribution characteristics of solid particles, and calculate the sliding velocity of particles in the impeller channel. The results show that at different solid particle concentrations, the solid volume fraction f in the front and rear cover plate area of the blade is high and that in the middle area is low; The solid volume fraction f decreases gradually from the working face to the back, and the solid particles are widely distributed in the inlet area. Due to the asymmetry of the volute structure, the particle concentration in the inlet area corresponding to the casing tongue is significantly higher than that in other areas; Due to the existence of circulating flow and through flow, the solid particles are distributed in a circular direction in the lateral cavity, and the particle concentration in the middle region is large; In the impeller area corresponding to the casing tongue, the sliding velocity of solid particles decreases with the increase of particle size, and the sliding velocity values of 0.5mm and 1.0mm particle sizes are close.

Computational Simulations of Spray Cooling with Air-Assist Injectors

A new computational procedure for simulating air-assist flat sprays with atomization is described and demonstrated for surface cooling applications. This procedure builds upon and utilizes findings from our previous work; particularly the integral form of the conservation equations which are used to derive explicit quadratic formulas for drop size. These formulations relate the local energetic state to initial drop size produced by primary atomization processes. In this manner, the local liquid and gas phase velocities prior to atomization are used in the quadratic formula to provide the initial drop size and the appropriate local velocities are utilized as the initial droplet momentum state in a discrete particle tracking algorithm. This procedure has been performed and compared to experimental data for drop size and velocity. This furnishes a platform to further study the effects of droplet distributions on heat transfer and momentum transfer between the spray and a heated metal surface. This approach is based on the conservation principles and generalizable, so that it can easily be implemented in any spray geometry for accurate and efficient computations of two-phase flows including spray cooling.

High-Speed Digital Photography of Gaseous Cavitation in a Narrow Gap Flow

The research of cavitation in narrow gap flows, e.g., lubrication films in journal bearings or squeeze film dampers, is a challenging task due to spatial restrictions combined with a high time-resolution. Typically, the lubrication film thickness is in the range of a few microns and the characteristic time for bubble generation and collapse is less than a few milliseconds. The authors have developed a journal bearing model experiment, which is designed according to similarity laws providing fully similar flow conditions to real journal flows while offering ideal access to the flow by means of optical measurement equipment. This work presents the high-speed photography of bubble evolution and transportation in a Stokes-type flow under the influence of shear and a strong pressure gradient which are typical for lubricant films. A paramount feature of the experiment is the dynamic variation (increase/decrease) of the minimum film thickness which triggers the onset of cavitation in narrow gap flows. Results presented in the work on hand include the time-resolved data of the gas release rate and the transient expansion of gas bubbles. Both parameters are necessary to set up numerical models for the computation of two-phase flows.

Coupling level-set with volume-of-fluid for interface computation of incompressible gas-liquid flows

In this study, a solver coupling the level-set and volume-of-fluid methods is developed for interface computation of incompressible two-phase flows on the OpenFOAM platform. It corrects the surface tension, density, and viscosity of the fluids with the level-set function synchronously. To examine the effect of density and viscosity corrections, an intermediate solver that only corrects the surface tension force is also developed. Two test cases, that is, a bubble rising freely in stagnant water and a drop impacting on a liquid surface, are performed to validate and compare the capabilities of the new solvers. It is found that the coupling solver which corrects all the fluids’ properties mentioned above has the best prediction accuracy, especially for Rayleigh jet issues. With the application of this solver, the mechanism for the bubble entrainment in drop impact on a liquid pool is explained.

Moving least-squares aided finite element method (MLS-FEM): A powerful means to consider simultaneously velocity and pressure discontinuities of multi-phase flow fields

We suggest a strategy to consider discontinuities in the two-phase flow calculations. Our approach comprises enhancing the shape functions of the finite element method (FEM) with the moving least-squares (MLS) interpolation functions. The new shape functions correlate a parameter at any arbitrary point to its surrounding nodes instead of an element's nodes. We name this strategy the "moving least-squares" aided "finite element method" (MLS-FEM).In a previous paper Mostafaiyan et al., we have employed the concept of the MLS-FEM to develop the PMLS (pressure shape function enhanced by the MLS interpolation functions) method, which predicts pressure discontinuities due to the surface tension forces. We take another additional step to consider velocity and pressure discontinuities in a domain with two different fluids. Therefore, we use the MLS technique to enhance the pressure (P) and velocity (V) shape functions. We name this scheme PVMLS (pressure and velocity shape functions enhanced by the MLS technique).We validate the PVMLS method with a stationary drop problem (as a benchmark). We show that the previous PMLS method fails to predict an accurate pressure or smooth streamlines by increasing the Capillary number and deviating from the unit viscosity ratio. However, the PVMLS method provides more accurate results since it considers velocity as a discontinuous parameter. Also, we compare the results of the PVMLS method at very high viscosity ratios (undeformable fluid) with a boundary-fitted single-phase problem. The reported similarities between the predicted pressure values and streamlines in both strategies demonstrate the reliability of the PVMLS method. Finally, we discuss that by employing the PVMLS method to calculate the velocity field, the interface advection will be more mass-conservative.

Simultaneous Measurement of Two-Phase Flow Parameters for Drift-Flux Model

The drift-flux model is widely used in study, calculation and design of two-phase flow. It is a highly efficient model that requires little computation resources. In the model, accurate calculation of the distribution parameter C0 and the drift velocity Vgj is a critically important factor. The calculation requires simultaneously measured data of phase velocity and void fraction distributions or profiles. By using currently widely used methods for two-phase flow measurement, satisfying the requirement is highly difficult. This paper presents novel results of simultaneous measurement of the phase velocity and void fraction profiles in a vertical round tube of 50 mm inner diameter. A combination measurement method has been developed. It comprises the multiwave Ultrasonic Velocity Profile (multiwave UVP) method and the Wire Mesh Tomography (WMT). Based on the measured data, C0 and Vgj have been calculated. They have been compared with those of the published experimental data and correlations. Analyses of the measured data have been carried out. For the first time, the analysis results reveal the variation of C0 and Vgj in the measured flow conditions. More importantly, the data obtained are also useful for the development and validation of the computational codes for two-phase flow.