Simulation Of Gas-liquid Two-phase Flow Research Articles

Void fraction measurement of slug flow using electromagnetic wave phase sensor based on optimized hybrid dielectric constant

The void fraction is one of the basic parameters to study the gas-liquid two-phase flow, which has great significance to the transportation of oil pipelines and the design of nuclear reactor cooling towers. However, due to the complex and variable nature of gas-liquid two-phase flow, accurately measurement of the void fraction has remained a challenging task in both scientific research and industrial applications. According to the principle of electromagnetic wave propagation, a coaxial line phase sensor was designed, a hybrid dielectric constant model based on the homogeneous flow was established and a void fraction based on hybrid dielectric constant model was proposed. The experiments were carried out on the high-precision gas-liquid two-phase flow simulation experimental setup at Hebei University, China (70 data points), and the void fraction model was inspected and verified. Five typical hybrid dielectric constant correlations were compared. Introducing the frequency weight, optimizing the hybrid dielectric constant model based on the Series – Parallel correlation, a new void fraction prediction correlation of slug flow was proposed and evaluated. The results indicated that the mean absolute percentage error (MAPE) of the new void fraction correlation is 1.02 % and the all of the relative errors are within ±5 % error band.

Progress on Numerical Simulation of Gas-Liquid Two-Phase Flow in Self-Priming Pump

The fundamentals of the design and operation of self-priming pumps, as indispensable equipment in industry, have been the focus of research in the field of fluid mechanics. This paper begins with a comprehensive background on self-priming pumps and gas-liquid two-phase flow, and it outlines recent advances in the field. Self-priming pumps within the gas-liquid two-phase flow state and the spatial and temporal evolution of the transient characteristics of self-priming pumps determine the self-priming pump self-absorption performance. Through mastery of the self-absorption mechanism, high-performance self-absorption pump products can be formed to provide theoretical support for the development of products. In current research, numerical simulation has become an important tool for analyzing and predicting the behavior of gas-liquid two-phase flow in self-priming pumps. This paper reviews existing numerical models of gas-liquid two-phase flow and categorizes them. Reviewing these models not only provides us with a comprehensive understanding of the existing research but also offers possible directions for future research. The complexity of gas–liquid interactions and their impact on pump performance is analyzed. Through these detailed discussions, we are able to identify the challenges in the simulation process and summarize what has been achieved. In order to further improve the accuracy and reliability of simulations, this paper introduces the latest simulation techniques and research methodologies, which provide new perspectives for a deeper understanding of gas-liquid two-phase flow. In addition, this paper investigates a variety of factors which affect the operating efficiency of self-priming pumps, including the design parameters, fluid properties, and operating conditions. Comprehensive consideration of these factors is crucial for optimizing pump performance. Finally, this paper summarizes the current research results and identifies the main findings and deficiencies. Based on this, the need to improve the accuracy of numerical simulations and to study the design parameters in depth to improve pump performance is emphasized.

Numerical Simulation of Gas-liquid Two-phase Flow in Emergency Rescue Drainage Pump Based on MUSIG Model

Numerical Simulation of Gas-liquid Two-phase Flow in Emergency Rescue Drainage Pump Based on MUSIG Model

Numerical study on the influence of the bucket offset angle on the flow field of Pelton turbines with six-nozzles

Abstract Pelton turbines are emerging as a primary means for exploiting ultra-high water head resources. The hydraulic performance of a Pelton turbine is determined by the design of its runner/bucket. Among the critical parameters that affect the hydraulic performance of multi-nozzle Pelton turbines is the bucket offset angle (α). To investigate the influence of bucket offset angle on the flow field of Pelton turbines with six nozzles, this study conducted unsteady numerical simulations of gas-liquid two-phase flow for various bucket offset angles, employing the VOF multiphase model combined with the SST k-ω turbulence model. The results reveal that as the bucket offset angle increases, the axial width of the water sheet formed by the current jet progressively widens, with a tendency to catch up with the water film formed by the previous jet during the torque rising stage. Moreover, the increased bucket offset angle causes the water sheet to distribute more closely to the bucket cutout, raising the risk of leakage from the cutout. Notably, at α= 10°, some of the water sheet has already flowed out of the cutout and collided with the subsequent jet.

Multi-site Garbage Collection Robot based on Machine Vision

At present, the problem of garbage disposal has become an urgent problem to be solved in the global energy technology revolution and transformation and development. The mainstream garbage removal methods are manual picking and mechanical collection, which has low cleaning efficiency and high cleaning cost. In order to realize the convenient and efficient recycling and cleaning of land and water garbage, a new propeller dynamics model is proposed. Through the structural strength analysis and gas-liquid two-phase flow simulation analysis, combined with the aerodynamic theory, the propeller impeller model was optimized and its suitable working parameters were explored. Based on the paddle impeller mechanism, combined with the visual recognition and classification system controlled by the algorithm combining YOLO and template matching, a multi-site garbage recycling robot based on machine vision was designed, which realized the intelligent and multi-step integration of garbage recycling, and provided a new research idea for improving the way of garbage cleaning.

Numerical simulation of gas-liquid two-phase flow in the N2-acetic acid system under elevated pressures and temperatures based on CFD-PBM model

The oxidation reaction process of p-xylene is studied under elevated pressure and temperature conditions using acetic acid as a solvent. In this study, a numerical simulation is employed, coupling Computational Fluid Dynamics (CFD) with Population Balance Modeling (PBM), to investigate the hydrodynamic behavior of gas holdup in the column of the N2-acetic acid system. The effects of superficial gas velocity, temperature, and solid holdup on the hydrodynamic behavior of the gas holdup in the column are discussed at the system pressure of 1.0 MPa, the superficial gas velocity ranging from 0.11 m/s to 0.27 m/s and the temperature between 25℃ and 105℃. In addition, a comparison is presented with the gas holdup of the air-water system. The results indicate that the simulated gas holdup aligns with the experimental value within the ±10% error range. Furthermore, the gas holdup increases with the increase of temperature and superficial gas velocity, while decreases with an increase in solid holdup. Additionally, the gas holdup in the N2-acetic acid system was found to be higher than in the air-water system. The research results of gas holdup and other hydrodynamic parameters in the N2-acetic acid system can offer valuable insights for the design and scale-up of the bubble column oxidation reactor.

Numerical simulation of gas-liquid two-phase flow in a disc pump under different inlet bubble diameters

Visual investigation and numerical simulation were utilized to analyze the internal flow pattern transformation and bubble diameter variation of a gas-liquid two-phase flow disc pump. The results reveal that increasing the intake volume fraction (IGVF) from 1.12% to 27.67% changes the flow pattern in the suction chamber from bubbly to agglomerate bubbly, slug flow, and separated flow. Due to the particularity of the impeller structure of the disc pump, the blades in the leaf area of the front and rear cover plates play a barrier role. The gas phase gathers most violently at the edge of the blade in the leaf area, while the flow channel in the middle leafless area is wider and has higher permeability. At 1500r/min and 7.11% inlet volume void fraction, the local void fraction extreme value of the front edge of the blade in the blade area of the front cover plate increases to three times the initial void fraction, while the void fraction extreme value of the middle section of the bladeless area decreases to two-thirds of the initial void fraction. This research can be used to analyze the gas phase distribution and migration law in the disc pump impeller.

Simulation Study on Dynamic Characteristics of Bubbles in Transformer Oil under Extremely Nonuniform Field

Bubbles in transformer oil seriously threaten the deterioration of internal insulation performance during its movement, leading to severe transformer failure. A gas-liquid two-phase flow simulation model is established based on the phase field method to study the effect of bubbles on the insulation performance of transformer oil. The dynamic characteristics of bubbles in transformer oil under extremely non-uniform electric fields are studied. The results show that the electric field force has a pushing effect on the bubble. As the voltage increases, the pushing effect is more significant, and the displacement distance of the bubble in the horizontal direction is larger. The velocity curve of a single bubble in the vertical direction shows an oscillating attenuation trend. The pushing effect of electric field force on the bubble causes the bubble velocity near the needle electrode to decrease, but the stretching effect increases the average bubble velocity. When the electric field strength is further improved due to the enhanced push-off impact of the electric field force on the bubbles, the bubbles will gather under the needle electrode to form cluster bubbles, further reducing the insulation performance of the transformer oil. This needs to be paid attention to in the design of the insulation structure to avoid the accumulation of bubbles caused by too high an electric field intensity at a particular place.

弱圧縮性手法を用いた多孔質体内混相流の大規模計算

The simulation of gas-liquid two-phase flow through a porous media by using multiple GPUs have performed. The ideal parallel efficiency of the weak scaling is achieved by applying weakly compressible method, which can avoid to solve Poisson's equation. We can calculate a wide range of parameters by introducing weakly compressible method. The conservative Allen-Cahn equation is solved to capture the gas-liquid interface by using the finite volume method to conserve the total mass of each phase. The simulations of gas-liquid two-phase flow through two-dimensional porous medium are performed by using our solver by using multi GPUs. Ideal parallelization efficiency is achieved by overlapping computation and communication time.

Numerical Simulation of Gas-Liquid Two-Phase Flow in Inlet Pipe Bend of Separator

Gas-liquid separators are widely used in oil and gas facilities to separate incoming liquid from gas for further processing. Droplet entrainment in the gas stream from a separator can have serious adverse consequences, for instance, damage to downstream rotating machinery. The prediction of separation performance of gas-liquid separators, which is important in order to avoid such operating issues, requires understanding of the mist characteristics in the upstream piping to the separator, and of the separation efficiency of the internals within the separator. The presence of bends in the inlet piping to a separator can have remarkable influence on the characteristics of mist flow entering the separator. Thus, evaluation of the fraction and size distribution of the mist in inlet piping bends is important in the assessment of the separator performance. This paper focuses on the prediction of the mist fraction and size distribution in the inlet piping bends as a first-step in the evaluation of separator performance. A numerical simulation method which reproduces the gas-liquid two-phase behavior in inlet piping bends is proposed. The effect of a bend upon the droplet entrainment and deposition in the piping is evaluated, which allows better understanding in the mechanisms of the two-phase flow within the bend. The predicted mist fractions and mist size distributions at an exit of the bend under various gas and liquid flowrates are compared with experimental data to validate the numerical simulation method and confirm its feasibility. The comparison show that the predicted mist fractions and mist size distributions agree with measurements, although there are some deviations from the measured results. From the results it is concluded that the numerical simulation can be applied for evaluation of the effects of inlet piping arrangements on mist fraction and mist size distributions, which is a key factor in the assessment of separator performance.

Numerical simulation of gas-liquid two-phase flow on an attitude control system

This paper introduced an attitude control system, which used saturated carbon dioxide as a medium. Through energy conversion, the system converted the pressure energy of gas-liquid mixed carbon dioxide into velocity energy and formed supersonic flow through the nozzle to generate thrust and torque. Compared with the compressed gas attitude control system, the carbon dioxide system had a better compelling specific impulse. With the continuous consumption of the medium, a large amount of liquid carbon dioxide was transformed into a gaseous state. Simultaneously, the pressure variation was slight, which was conducive to control. With a higher initial temperature, more liquid carbon dioxide was consumed, and the thrust was more significant under the same conditions of tank volume and carbon dioxide mass; meanwhile, the faster the temperature decreased.

Numerical simulation of gas-liquid two-phase flow impacting fixed structure by CLSVOF/IB method based on OpenFOAM

Numerical simulation of gas-liquid two-phase flow impacting fixed structure by CLSVOF/IB method based on OpenFOAM

Prediction of Laminations in Zinc Alloy Die-Casting by Gas-Liquid Two-Phase Flow Simulation

Prediction of Laminations in Zinc Alloy Die-Casting by Gas-Liquid Two-Phase Flow Simulation

Numerical and experimental simulation of gas-liquid two-phase flow in 90-degree elbow

In the present research, the effects of four 90-degree horizontal elbows with different curvature radii (17, 34, 51, and 68 cm) and an identical rectangular cross-section (20 * 34 mm) on a gas–liquid slug flow pattern have been studied experimentally and numerically. Gas and liquid superficial velocities in numerical and experimental parts were set in 2.5 m/s and 0.44 m/s, respectively. In the computational fluid dynamics section, the distribution of volume fraction, velocity, pressure, turbulence intensity, and swirling intensity parameters were investigated using the VoF model and the SST k-ω method. Experimental studies were conducted utilizing pressure data and signal processing tools to study the dominant frequency of slug flow alongside bandwidth distribution as well as the Shannon entropy. The results exhibited that although the dominant frequency of slug flow did not change after passing the 90-degree elbow, the frequency signal's bandwidth increased. In this regard, the application of Shannon entropy quantity revealed that the frequency distribution signal experienced a greater increase in bandwidth as the elbows’ curvature radius increases. The turbulent intensity of the elbows’ outlet reveals that by increasing the curvature radius, the flow field behaves smoother. Also, swirling intensity distribution shows that decreasing the elbow radius leads to increment in the swirling intensity.

Numerical simulation of gas-liquid two-phase flow in the micro-fracture networks in fractured reservoirs

The fracture network in fractured reservoirs is the main channel for fracturing fluid intrusion and gas flow, and the presence of liquid has a great influence on the gas flow pattern, and the gas flow shows more diversity in fluids with different properties such as fracturing fluid or formation water. In order to study the characteristics of gas-liquid two-phase flow in the microfracture network of the fractured gas reservoir, the topology of the microfracture network is simplified to T-junction and Y-junction. Based on the volume of fluid model, the gas-liquid two-phase flow interface is tracked. The model is solved by computational fluid dynamics software OpenFOAM, and the correctness of the model is verified by comparing it with laboratory microscopic experiment results. The flow characteristics of the gas phase in different fluids at the microscale and the influence of fluid parameters on flow pattern are analyzed. The results show that the properties of the liquid phase have a strong influence on the gas flow pattern, and the two-phase flow velocity and the properties of fluid parameters affect the gas flow to reach the stable state. The findings of this study can be used for reference to analyze the flow characteristics of gas in fracturing fluid and the flowback technology of fracturing gas well.

Effects of turbulence fluctuation intensity in bioreactor of sewage treatment on physical and chemical properties of biofilms.

The flow velocity plays an important role in the growth and characteristics of biofilm in the bioreactor as well as its treatment efficiency, which has been a hot research topic. In a sewage treatment bioreactor, the type of flow is usually turbulence. According to the methods of Reynolds decomposition, the flow velocity of turbulence consists of the time-mean velocity and fluctuation velocity, which usually exist simultaneously in real flow. However, the current research on the influence of turbulence flow velocity mainly focuses on the time-mean velocity, while the fluctuation velocity has not been reported because of very difficult to control. To this end, in this paper, a laboratory oscillating-grid turbulence (OGT) bioreactor with zero time-mean velocity and only fluctuation velocity was designed. In this bioreactor, the fluctuation velocity could be easily manipulated by varying the operational parameters of the grid. Based on the numerical simulation of Gas-liquid two-phase flow, the distributions of fluctuation velocity and corresponding turbulence fluctuation intensity, gas holdup, and Reynolds stress were obtained. After that, the effects of the turbulent fluctuation intensity on the biofilm thickness, density, and composition of extracellular polymeric substances (EPS) were studied experimentally. The results showed that turbulent fluctuation had a significant effect on the physical and chemical properties of biofilms, and the fluctuation velocity promoted the increase in the biofilm density and the content of protein and carbohydrates in EPS. This study was intended to provide theoretical support for the design and operation optimization of bioreactors.

Transient numerical simulation of gas-liquid two-phase flow in long distance water supply pipeline

To reveal the gas-liquid two-phase flow characteristics in water supply pipeline due to the rugged terrain, flow pattern, pressure, velocity, turbulent kinetic energy and turbulent energy dissipation rate of 6 key sections and 4 profiles were simulated and analysed on the conditions of with and without exhaust valve. The results showed that water cannot flow smoothly without exhaust valves at sections 1-1, 2-2 and 3-3, while that flows smoothly at sections 4-4, 5-5 and 6-6. For sections 1-1, 2-2 and 3-3, water can only cover less than 50% of the pipeline cross section when the exhaust valves were not set, and various backflow zones can be observed in these sections, which can increase the resistance of the water flow. The turbulent kinetic energy of the cross sections 1-1, 2-2 and 3-3 were 0.87, 1.02 and 0.09 m2/s2, which can decrease to 0.0018, 0.0017 and 0.0017 m2/s2, respectively, after the exhaust valves were set. Meanwhile, the pressure in different cross sections reduced by 1 to 10 kPa and the streamline were nearly uniform and straight for the main flow in the pipe with the exhaust valves. The reverse vortex disappeared and the velocity distribution of the main flow was more uniform in these sections.

Simulation of Gas-Liquid Two-Phase Flow in Metallurgical Process

Simulation of Gas-Liquid Two-Phase Flow in Metallurgical Process

Numerical simulation of gas-liquid two-phase flow in gas lift system

The gas-lift system has a lot of significant advantages in sewage treatment, deep well oil recovery, liquid metal cooled reactor and magnetohydrodynamic power converters. The densities of different liquid media and gas media have great influences on the performance of gas lift system. Therefore, based on Fluent simulation software, using Euler model and <i>k</i>-<i>ω</i> SST (shear stress transport) turbulence model, the gas-liquid two-phase flow behaviors in nitrogen-water, nitrogen-kerosene, nitrogen-mercury and air-water, argon-water, nitrogen-water of gas lift system are studied. The rules of gas volume fraction and liquid flow rate at lifting pipe, liquid radial velocity at lifting pipe outlet, promoting efficiency are analyzed. The results are shown as follows. 1) In the nitrogen-water, nitrogen-kerosene and nitrogen-mercury system, the higher the density of liquid medium, the smaller the gas volume fraction in the lifting pipe is; the greater the flow rate of lifting liquid, the higher the promoting efficiency is. 2) In the air-water, argon-water and nitrogen-water systems, the higher the density of gas medium, the smaller the gas volume fraction in the lifting pipe is; the larger the flow rate of lifting liquid, the smaller the peak value of promoting efficiency is. 3) With the increase of gas flow rate, the liquid radial velocity at the lifting pipe outlet increases with overall fluctuation rising. Finally, the liquid velocity near the center of pipe axis is large, near the pipe wall is small. These research results provide the scientific theoretical basis for optimizing the gas lifting technology in applications such as sewage treatment, deep well oil recovery, liquid metal cooled reactor and magnetohydrodynamic power converters.

Prediction of Laminations in Zinc Alloy Die-Casting by Gas-Liquid Two-Phase Flow Simulation

In the manufacturing process of zinc alloy die-casting, laminations are a serious problem because they cause blister defects and the deposition of zinc on the mold surface. Thus, it is very important to analytically predict the risk of lamination formation before determining the mold design. In this study, we proposed a criterion for predicting the locations of laminations. The criterion value is estimated from the result of a molten metal flow simulation and can indirectly predict the locations of laminations. As the analytic method in the mold-filling simulation, we adopted a gas-liquid two-phase flow model with a finite element method, and the Cahn-Hilliard equation was adopted to determine the interface between the gas and the liquid. We predicted the locations of laminations for two different types of gating system using the mold-filling simulation. The validity of the proposed criterion for laminations was confirmed by comparison of the results of the simulation and the observation of laminations after practical die-casting.