Characteristics Of Gas-liquid Two-phase Flow Research Articles

Investigation of the minimum filling amount of ionic liquid in the multi-stage ionic liquid compressor

Ionic liquid compressors are the ideal solution for hydrogen refueling stations, and multi-stage compression is an inevitable choice for achieving high-pressure refueling, such as 90 MPa level. However, the initial filling amount of the ionic liquid in the compression chamber is lacking basis as the characteristics of gas-liquid two-phase flow during the reciprocating movement of the liquid piston are not understood. This study numerically investigates the variation characteristics of the gas-liquid interface in the compression chambers under different structural and operating parameters of a five-stage ionic liquid compressor. Based on the fluctuation feature of the phase interface, the minimum liquid piston heights in each stage that ensure effective sealing for the compression chamber with different stroke-to-diameter ratios (r) are determined. Finally, the mathematical relationship for calculating the minimum ionic liquid filling amount related to structural parameter r and suction pressure is established, which provides guidance for the design of the ionic liquid compressor.

Gas-liquid flow and mass transfer characteristics in improved heart-shaped structure microreactor

The gas-liquid two-phase flow and mass transfer characteristics in heart-shaped structure microreactor were visually investigated in an Advanced Flow Reactor (AFR). Three various flow patterns were observed in the experiment: Taylor-bubble flow, Taylor-flow, and unstable broken flow. The experiment observed that the bubbles only broke steadily under the action of the first heart-shaped unit obstacle; while in the latter heart-shaped units, the larger bubbles would break resulting in the unstable broken flow. The efficiency of CO2 absorption increases as the gas-liquid two-phase flow rate ratio decreases and the solution concentration rises. The volume mass transfer coefficient increases with the increase of the gas-liquid two-phase flow rate ratio and the solution concentration. The absorption efficiency and mass transfer coefficient in channel 2 with two rows of heart-shaped units is greater than channel 1 with one row of heart-shaped units. Additionally, there exists an optimal performance ratio for reactor under the appropriate gas-liquid flow rate ratio.

Optimal design and performance analysis of anode flow channels in proton exchange membrane water electrolyzers

In proton exchange membrane water electrolysis, the water/oxygen distribution characteristics in the anode channel significantly affect the electrolyzer performance. In this paper, a three-dimensional two-phase non-isothermal numerical model of the electrolyzer is established, in which the reaction kinetics equation is modified theoretically and is validated experimentally. Two novel anode channel structures (Straight-through turbulent flow channel and Mesh-like structured flow channel) are designed and their multiphysical field distribution characteristics are compared with the traditional straight-through flow channel. Results show that, for Straight-through flow channel structure, the liquid water saturation and temperature gradient between the under-channel and under-rib areas are large, resulting in bubble accumulation under the ribs, deterioration of heat and mass transfer, and harming the electrolyzer reaction rate. The two novel structures both have velocity component perpendicular to the channel flow direction, promoting the expulsion of oxygen accumulated in the anode porous electrode, contributing to more uniform distribution characteristics of gas-liquid two-phase flow and current density. At 2.5 V, the current density of Straight-through flow channel, Straight-through turbulent flow channel, and Mesh-like structured flow channel are 4.12, 4.14, and 4.53 A/cm2, respectively. The excellent heat and mass transfer characteristics enable the Mesh-like structured flow channel to have the best electrochemical performance.

Research on test method of multi-channel ultrasonic wave detection for gas well injection volume

In the early stage of natural gas extraction, the fracturing and blowout process is often used to obtain stable production. However, during the fracturing process, natural gas combustion is frequently directly released, which causes significant pollution to the environment and a waste of resources. In order to measure the flow rate of the gas-liquid mixture in the process of gas well blowout, a multi-channel velocity measurement model is established. The multi-channel sensor structure is designed based on an analysis of the gas well blowout process and fluid configuration simulations. The influence of pipe diameter on the flow characteristics of gas-liquid two-phase flow was analyzed by FLUENT software. The simulation results show that the distribution of flow velocity in a gas-liquid two-phase flow tube is not uniform, the flow velocity of different flow layers is different, and the stratification phenomenon is more obvious with the increase of pipe diameter, highlighting the necessity of multi-channel measurements. Therefore, we developed a gas-liquid two-phase flow velocity measuring device. The experimental results demonstrate that accurately describing velocity in the tube can be achieved by measuring velocities in different channels using the gas-liquid two-phase flow velocity measurement device.

Fluid dynamics and energy efficiency of submerged combustion process for treating wastewater with high salinity and COD concentration

Focusing on submerged combustion technology for the treatment of high salinity and high chemical oxygen demand (COD) wastewater, this study explores the characteristics of gas-liquid two-phase flow and heat transfer during the submerged combustion process, employing both experimental and numerical simulation methods.Consequently, the impact of essential parameters on the efficacy of submerged combustion in treating wastewater was analyzed. The experimental results show that increasing the fuel flow rate and immersion depth is beneficial to improve the temperature rise rate and shorten the evaporation time. With the increase of the organic solution flow rate and the initial COD value of the organic solution, the COD removal rate decreased, and the effect of the organic solution flow rate on the COD removal efficiency was more obvious. The use of a flat orifice plate or tapered orifice plate immersed tube structure can improve the thermal efficiency by over 10%. However, it is not conducive to the stability of the pressure in the combustor, increasing the fluctuation of the liquid level. Compared with that of traditional single-effect evaporation crystallization, the energy consumption of the submerged combustion device is decreased, and the total operation cost is reduced by 22.5%.

Experimental study on leakage characteristics of gas-liquid two-phase flow in a horizontal pipe

Oil and gas pipeline leakage accidents caused by aging and third-party damage have increased, resulting in polluting the ecological environment and jeopardizing life and property safety. A detailed and systematic investigation on the leak characteristics of oil and gas two-phase pipelines is significantly urgent. The leak experiments were performed on a horizontal tube with a diameter of 32 mm. There was a 3 mm round leakage hole at the bottom of the tube. The distance of the leakage hole from the pipe inlet was 4.8 m. Three inlet flow patterns, including stratified flow, slug flow, and annular flow via adjusting the gas superficial velocity (1.73 m/s ≤ USG ≤ 24.19 m/s) and liquid superficial velocity (0.017 m/s ≤ USL ≤ 0.415 m/s), were obtained. The conclusions point out that the type of leakage, whether it is mainly liquid or both gas and liquid, depends on the USG. The degree of phase separation in stratified flow is the greatest among the three inlet flow patterns, with a maximal phase separation efficiency (η) of 0.403. Slug flow has the least phase separation degree. Interestingly, the η is directly proportional to the inlet mass fraction only for slug flow. The harmonic frequency that appeared in the power spectral density curves for the pressure difference of leakage hole in slug flow, indicates that leakage is not a standard periodic event. The liquid velocity loss is primarily related to the gas leakage mechanism. These findings can provide new insights into two-phase pipeline leak detection and accident consequence prediction.

Study of gas-liquid two-phase flow characteristics in hydrate-bearing sediments

The characteristics of gas-liquid two-phase flow in hydrate-bearing sediments (HBS) are critical for natural gas hydrate production. This study experimentally investigates the flow patterns in the presence of hydrates and employs the phase field method for accurate simulations. Additionally, flow pressure differences in a capillary model were analyzed, and the impacts of occurrence patterns, saturation, and wettability of hydrates were investigated by numerical simulation. The results show that flow patterns are predominantly influenced by flow velocity. At high flow rates (Reynolds number >10), different gas-liquid ratios result in a variety of flow patterns, including annular, Taylor, and bubble flow. However, at lower flow rates (Reynolds number <10), the flow pattern consistently manifests as Taylor flow, regardless of gas-liquid ratio variations. Notably, the Jamin effect (a significant pressure differential caused by hydrates within the flow) was observed, which intensifies with increasing hydrate saturation and decreasing contact angle. Pore-filling hydrate patterns, in contrast to grain-coating, exhibit a greater number of gas-liquid interfaces, leading to larger pressure differences and a more evident Jamin effect. These findings aid in understanding the fluid migration in HBS and help estimate the natural gas production capacity.

Investigation on gas-liquid two-phase frictional pressure drop in pipeline riser

The pressure drop characteristics of gas-liquid two-phase flow in pipeline-risers are important to the design optimization of marine risers lifting oil and gas. In this study, experimental investigation on single-phase and air-water two-phase flow pressure drop characteristics in vertical and S-shaped risers have been carried out in a long-distance pipeline with the gas superficial velocities ranging from 0.03 to 6.2 m/s and the liquid superficial velocities from 0.02 to 1.3 m/s. The test loop with 50 mm i. d. Consists of a horizontal pipeline with 114 m in length, followed by a 16 m downward inclined section, and ended at a riser. The downward section is adjustable in inclination with various angle of −2°, −3°, −4° and −5° with respect to horizontal. A vertical riser and an S-shaped flexible riser were used in the experiment. The effects of flow and geometry parameters on two-phase frictional pressure drop multiplier are studied. For flow parameters, the two-phase frictional pressure drop multiplier increases with increasing the inlet gas and liquid superficial velocity. For geometric parameters, the two-phase frictional pressure drop multiplier in S-shaped riser is larger compared to that in straight vertical riser. The existing correlations reported in the literature are evaluated. A single-phase friction factor correlation and a two-phase frictional pressure drop multiplier correlation for pipeline-riser system are developed. Comparison of the predicted value and the measured results shows good agreements.

Numerical Simulation Study on Flow Characteristics of Multistage Centrifugal Pumps under Different Inlet Gas Void Fractions

The flow characteristics of multistage centrifugal pumps in transporting gas–liquid mixed media are highly complex; particularly, the unstable flow of the passage at high gas contents exacerbates energy losses, leading to a decrease in pump efficiency and stability. The excess energy loss in the pump is not conducive to the concept of sustainable development. In this study, a numerical simulation of multistage centrifugal pumps was conducted based on the Euler–Euler heterogeneous two-fluid model. This research revealed that gas primarily accumulates on the suction side of each impeller stage, and the gas distribution decreases progressively with each stage. As the interstage gas volume fraction (IGVF) increases, the gas accumulation within the pump becomes more pronounced. The gas volume fraction of each component is negatively correlated with the flow rate, and the change is more obvious in the impeller. The turbulent kinetic energy distribution inside the impeller is positively correlated with the gas distribution. There is a large fluctuation at 0.6Q and 0.8Q, and the distribution of the impeller vortex is asymmetric. However, the impeller has a lower turbulent kinetic energy near 1.2Q, which indicates that the emergence of gas in the medium increases the high-efficiency area of the multistage pump to a certain extent. This paper reveals how the gas phase is distributed, how energy is lost in the multistage pump, and the gas–liquid two-phase flow characteristics in the pump, which have certain guiding significance for the design and working-condition adjustments of the gas–liquid mixed pump.

Experimental study on ultrasonic wave propagation characteristics of gas-liquid two-phase flow in riser annulus

Deepwater drilling projects face challenges such as delays in gas kick monitoring and a high risk of well control failure. How to monitor gas kicks as early and accurately as possible is one of the keys to preventing significant accidents such as well blowouts. Monitoring gas kicks at risers is a promising method for early monitoring of gas kicks in deepwater drilling. In this paper, by constructing an experimental device for ultrasonic gas kicks monitoring of the riser, the response law of the ultrasonic signal to the gas-liquid two-phase flow was tested under different air intake, drill pipe rotation speeds, and liquid flow rates. This was done by constructing an experimental riser ultrasonic gas kick monitoring device. The signal-to-noise ratio and the root-mean-square error are used as measurement standards, and the wavelet threshold noise reduction method is used to reduce noise-containing signals. The ultrasonic sensitivity characteristics of the gas-liquid two-phase flow are demonstrated by analyzing the signal in the time domain and frequency domain: peak amplitude, attenuation coefficient, wave velocity, and fundamental frequency. A non-linear relationship exists between peak amplitude, fundamental frequency, and air intake, whereas an approximately linear relationship is evident between the attenuation coefficient and wave velocity with air intake. A quantitative characterization relationship between ultrasonic characteristic parameters and air intake was obtained by conducting a multiple regression analysis using the least-squares method on the attenuation coefficient, wave velocity, fundamental frequency, and air intake. Experiments demonstrate that the relative error between the actual air intake of 86.4 % of the test data group and the theoretical air intake determined based on the quantitative characterization relationship is less than 10 %.

Effect of Blade Twist on The Flow Characteristics of Gas-Liquid Two-Phase Flow in a Spiral Axial Flow Pump

The mixing of oil and gas forms the foundation of deep-sea oil and gas extraction and transportation. However, traditional conveying equipment has low efficiency and high failure rates. In this study, a spiral axial flow gas and liquid multiphase pump was used as the base model. The Eulerian multiphase flow model and RNG turbulence model were used for numerical simulations to analyze the internal flow field of the multiphase pump. A modification scheme was proposed to twist the airfoil shape and create a twisted vane. The twisted blade with the center of the hub-side flange chord length as the twisting center was twisted in the counterclockwise direction to help reduce the relative volume of gas in the flow channel. When the twisted vane with the hub-side airfoil type trailing edge point as the twisting center was twisted in the suction side direction, it helped to accelerate the movement of the gas-liquid mixture at the trailing edge of the back of the vane and further reduced the low velocity zone at the back of the vane. When the twist center is located at the hub side wing type trailing edge point of the twist vane, the twist degree is 0.214. This results in the maximum head and efficiency of the pump, improves gas phase aggregation phenomenon, and enhances the performance of the multiphase pump.

Experimental investigation on interface characteristics of gas-liquid two-phase flow in a kilometer-scale pipeline

It is greatly essential for the construction of multiphase flow models and the flow assurance of oil and gas pipelines to study the fully developed interface characteristics at different flow patterns in the industrial-grade long-distance pipelines. In this paper, the phase interface structures of dispersed bubble flow and three slug sub-flow patterns are captured by visualization method in a 46 mm ID, 1657 m long pipeline. It is found that the interface characteristics between elongated bubbles and liquid film can effectively distinguish different slug sub-flow patterns, and a quantitative division criterion between different slug sub-flow patterns is proposed. The transition boundary prediction model for dispersed bubble flow and slug flow in long pipeline is established, and the flow pattern map at high liquid velocities and low gas velocities is plotted. With the increase of two-phase mixture velocity, the radial position of elongated bubble head approaches the middle of the pipeline, and the liquid film thickness is stably distributed around 0.37 D. The correlations that predict the radial position of elongated bubble head, liquid film thickness, and elongated bubble velocity for long pipeline are established, with maximum error less than 15 %.

Influence of vibration on transient flow characteristics of gas-liquid two-phase flow in inclined pipes

As an advanced method of transportation globally, pipelines play a significant role in the energy sector of many nations. Given the rapid development of offshore oil and gas engineering, it is critical for researchers to focus on the dynamics of pipelines and the flow characteristics of internal fluids under oceanic conditions. In this paper, a gas-liquid two-phase flow numerical model was developed to simulate transient flow characteristics in an inclined pipe at different vibration conditions based on CFD dynamic mesh technology. The CFD model was verified against experimental data, showing that the numerical simulation predicts average pressure drop within 10 % of experimental data. Parametric studies were conducted based on the CFD analysis, including vibration direction (horizontal, vertical, and inclined), vibration amplitude (0.5D∼1.5D) and flow velocities (jsg=0.5∼1.0m/s, jsl=0.1∼1.0m/s). Meanwhile, the downhill and uphill sections of the pipeline were considered. The results indicated that inclined vibration had the most substantial impact on flow, followed by horizontal vibration and vertical vibration. The changes of average liquid holdup were closely related to flow pattern under vibration conditions. These vibration conditions significantly effected pressure fluctuations and secondary flow. The impact of vibration on transient flow heightened with increased vibration amplitude. In addition, transient flow behaviors showed periodicity, and the evolution period was consistent with the vibration period. These findings are helpful to understand the transient flow behaviors in inclined pipe under vibration conditions.

Numerical study of transient flow characteristics of gas-liquid two-phase flow in inclined upward tube under periodic vibration

The transient flow characteristics of gas-liquid two-phase flow in inclined upward tubes exhibit a high degree of complexity. The tube vibration caused by multiple uncertain factors, such as seawater impacts or subsea earthquakes, poses more significant challenges for flow safety assurance. Thus, it becomes increasingly crucial to explore the transient flow characteristics of gas-liquid two-phase flow in inclined upward tubes under various vibration conditions. In this paper, the transient flow characteristics of gas-liquid two-phase flow in an inclined upward tube under different vibration conditions are numerically studied based on CFD dynamic mesh technique. In the current study, the studied parameters include vibration direction (heaving, transverse and coupling), vibration amplitudes (0.5D, 1.0D and 1.5D), and inlet velocity (jsg=0.5∼1.0m/s; jsl=0.1∼1.0m/s). The transient flow structure, cross-sectional void fraction and pressure drop are analyzed. The findings indicate that the transient flow structure of the slug flow demonstrates periodic variation characteristics under transverse and coupling vibrations, and the cross-sectional void fraction increase. For transition flow, the cross-sectional void fraction increases under transverse and coupling vibrations, while displays an increase initially and subsequently a decrease significant with an increase in the heaving vibration amplitude. Additionally, all considered vibration conditions intensify the pressure drop of the transition flow and decrease the cross-sectional void fraction of the turbulent flow.

Numerical investigation of the water draining process pushed by gas for several manifolds with different header-diameter

In the EAST (Experimental Advanced Superconducting Tokamak), the manifolds play an important role in the blow-out process, which directly affects the dryness of the plasma facing components (PFCs) and the entire drying system. This will cause corrosion of PFCs and coolant leakage, which will seriously affect the safe operation of the device. Therefore, it is necessary to study the gas–liquid​ two-phase flow characteristics of the manifold during the blowout process. In this paper, the CFD (Computational Fluid Dynamics) method was used to simulate the gas–liquid blowout process of the manifold with different header-diameters, and to discuss the influence mechanism of the change of header-diameter on the blowout effect. Under the boundary condition of a gas supply with a certain pressure difference, it can be found that enlarging the header-diameter can enhance the uniformity of the flow of branches, improve the inlet gas flow rate of manifold, which conductively improve the dryness of the manifold. The research results in this paper will provide reference for improving the dryness of internal components and drying systems, and also for the construction of future fusion reactor drying systems.

Numerical method for gas-liquid two-phase flow with phase change heat transfer considering compressibility using OpenFOAM

The numerical simulation of phase change heat transfer is important for predicting the gas-liquid two-phase flow and heat transfer characteristics and optimizing the phase change heat dissipation system. For the isovolumetric phase change heat transfer process, the compressibility of the gas phase has a significant impact on the simulation accuracy. A numerical simulation method of flow and phase change heat transfer considering gas-liquid two-phase compressibility is established based on VOF method using OpenFOAM in this paper. This method introduces a generalized phase change source term and a compressible source term to improve the isoAdvector geometric reconstruction algorithm and establishes a method for capturing the phase interface of a compressible two-phase flow. The phase change flux based on the phase interface is converted into a phase change source term based on the unit volume by calculating the phase interface density. The compressible term of the governing equation is constructed and its implicit discrete method is proposed. The coupling between velocity and pressure is realized based on the PISO algorithm. A numerical calculation method for phase change heat transfer of compressible two-phase flow is established. The effectiveness and accuracy of the proposed numerical method for predicting the heat transfer characteristics of phase change flows are verified by the simulation of vertical flat film condensation and film boiling. The numerical simulation results are in good agreement with the experiment. Compared with the other numerical simulation methods, the proposed method considering the influence of the compressibility of the gas phase on the flow and heat transfer characteristics in the heat pipe has high accuracy in predicting the gas-liquid two-phase flow, capturing the evolution characteristics of the phase interface and predicting the phase change heat transfer. The numerical simulation method can provide algorithm support for the numerical simulation of compressible two-phase flow phase change heat transfer and the design of a phase change heat dissipation system.

Identifying Flow Patterns in a Narrow Channel via Feature Extraction of Conductivity Measurements with a Support Vector Machine.

In this work, a visualization experiment for rectangular channels was carried out to explore gas-liquid two-phase flow characteristics. Typical flow patterns, including bubble, elastic and mixed flows, were captured by direct imaging technology and the corresponding measurements with fluctuation characteristics were recorded by using an electrical conductivity sensor. Time-domain and frequency-domain characteristics of the corresponding electrical conductivity measurements of each flow pattern were analyzed with a probability density function and a power spectral density curve. The results showed that the feature vectors can be constructed to reflect the time-frequency characteristics of conductivity measurements successfully by introducing the quantized characteristic parameters, including the maximum power of the frequency, the standard deviation of the power spectral density, and the range of the power distribution. Furthermore, the overall recognition rate of the four flow patterns measured by the method was 93.33% based on the support vector machine, and the intelligent two-phase flow-pattern identification method can provide a new technical support for the online recognition of gas-liquid two-phase flow patterns in rectangular channels. It may thus be concluded that this method should be of great significance to ensure the safe and efficient operation of relevant industrial production systems.

Study on the vertical oscillatory gas-liquid two-phase flow and heat transfer characteristics

Exploring the flow and heat transfer characteristics of oscillations will help to evaluate the dynamic behavior and safety of thermal management systems (TMS) in automobiles, ships, and aircraft. Faraday waves is a phenomenon that standing waves oscillate with half of the driving frequency under specific oscillation conditions. The current work combines both, studying the influence of oscillation parameters of Faraday waves on heat transfer since the oscillatory liquid surface and the shaking of the liquid-filled container frequently occurs in practical engineering applications. A numerical simulation on heat transfer characteristics under different vibration parameters was carried out in this study. The results demonstrate that oscillation has a promotion effect on the heat transfer coefficient. The influence of the driving frequency on heat transfer will be affected by the driving amplitude. When the driving amplitude is greater than 0.83 mm or the driving frequency is greater than 22 Hz, the waveform will change from periodic and regular to disorder and turbulence, and the heat transfer between the two-phase flow will be significantly enhanced. In the range of oscillation parameters covered in this study, increasing the driving amplitude is more effective than increasing the driving frequency for enhancing heat transfer. And when the driving amplitude is big enough, such as A = 1.03 mm, the heat transfer intensity increases to about 1.5–2 times as against A = 0.43 mm. Therefore, when considering the design of TMS, the dynamic empirical correlations proposed by this study can offer some useful guidance.

Bibliometric analysis for research trends and hotspots in heat and mass transfer and its management of proton exchange membrane fuel cells

Heat and mass transfer and its management is an important part of proton exchange membrane fuel cells (PEMFCs), which has a decisive impact on the performance and durability of PEMFCs. In order to comprehend the research progress and hotspots in heat and mass transfer and its management of PEMFC, 3977 literatures related to this field (up to 26th July 2022) were obtained from the Web of Science Core Collection database. Based on the mapping knowledge domain (MKD) and the VOSviewer visualization software, the number of publications, citation frequency, keyword co-occurrence, and clustering were counted and analyzed. The research progress, hotspots, and trends in the field of heat and mass transfer and its management of PEMFC were then summarized. The results show that since 2000, the annual quantity of publications in this field has experienced a period of increasing, decreasing, and then increasing, while in recent years, it is in a period of rapid growth. This field has received extensive attention in China, the United States and Canada, with many researchers, among which the quality of publications from Canada is relatively high. Related studies have been published in energy and electrochemistry journals such as the International Journal of Hydrogen Energy and the Journal of the Electrochemical Society. The Journal of Power Sources is the authoritative journal in this field with the largest total number of publications and total citation frequency. According to the keyword co-occurrence network map, there are four clusters in this field, and each cluster has a different research focus. Among them, cluster 4 has only one keyword, humidification. This field can be roughly divided into three research stages, namely, the exploration of gas–liquid two-phase flow characteristics in PEMFC, the development of PEMFC heat and mass transfer and its management, and the water and heat management and performance optimization of PEMFC. In order to achieve the development goals of high-power density, high reliability and long-life of PEMFC, the research of the third stage should be further deepened in future work. This paper will provide reference for scholars engaged in the field of PEMFC heat and mass transfer and its management.

Numerical Analysis on Flow Characteristics of Gas-liquid Two-phase Flow in a Vertical Pipe with Downward Stream

Through this paper, a 3D simulation together with experimental observation was conducted to study two-phase flow in a vertical tube. OpenFOAM software was employed to analyze air and water. Main flow stream was downward which was considered to be within a vertical pipe of 10 mm in diameter. Study included two inputs for flows: upper input for water and side input for air. Several states with various mass fluxes for both water and air were studied. Based on physics of the issue, numerical simulation was considered to be time-dependent. Obtained results showed that when air velocity occupied lower values, air momentum cannot overcome water momentum leading in small slugs. When airflow velocity was more than water flow rate, it dominated water flow and consequently could affect mainstream direction. Also, velocity graphs on centerline represented that going forward in time, velocity magnitude experiences a significant value of fluctuations and large oscillations occur next to outlet. Comparing experimental and numerical results, approximately 9% differences can be found which showed suitable agreement. Results showed that at initial steps, void fraction faces a significant jump in values. Intensity of this change in void fraction values was higher in lower water velocity. Indeed, by increment of water velocity, inertial forces associated with liquid phase find a dominant role in overall hydrodynamics of the gas-liquid flow. Also, it is obvious that flowing manner in cases 1, 2, and 3 are similar but after case 4, flow pattern varies. These changes are more considerable in cases 5 and 6.