Transient Flow Behavior Research Articles

Transient Analysis of Fluid Flow, Solidification, and Inclusion Behavior in Electromagnetically Stirred Bloom Caster Mold Using Bifurcated Submerged Entry Nozzle

Herein, the effect of bifurcated submerged entry nozzle (SEN) port angles on transient flow, solidification, and inclusion behavior in a bloom caster mold with electromagnetic stirring (EMS) is investigated. A 3D numerical model is developed to simulate the process, including time‐varying electromagnetic field and Lagrangian inclusion tracking approach, by varying inclusion density and size. The inclusion is modeled to be entrapped in the solidified shell when primary dendrite arm spacing (PDAS) is greater than inclusion size. As compared to the case without use of EMS, the percentage of shell thickness at the strand outlet is seen to increase by 22.18%, 9.45%, 8.03%, 9.31%, and 13.40% for different port angle values of 0°, 15°, 20°, 25°, and 30°, respectively, with EMS. The results show that EMS significantly influences the flow behavior by generating the swirl flow pattern that hinders the movement of inclusion downward in the domain. The bifurcated SEN with 30° port angle (without EMS) is seen to reduce inclusion entrapment and hence enhance inclusion removal. The outcome of present research may provide useful insights for optimizing the parameters of bloom caster mold to improve product quality, reduce production costs, and increase overall efficiency.

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.

Modeling Transient Flow Behavior of Off-Center Fractured Well with Multiple Fractures in Radial Composite Gas Reservoirs

Summary Vertical hydraulic fracturing is widely used to develop low-permeability gas reservoirs. Uneven distribution of formation permeability and stress leads to multiple-wing hydraulic fractures with different lengths, which results in the wellbore not being the center of the circular stimulated reservoir volume (SRV) region. Therefore, to simulate the wellbore pressure of this phenomenon, a semianalytical model of the off-center multiwing fractured well in radial composite gas reservoirs is presented and the corresponding solution method is shown. The model is verified with the numerical solution, and eight flow regimes can be distinguished under the ideal case, which includes bilinear flow, fracture interference, linear flow, radial flow of inner region, transition flow of inner region, and radial flow of inner region. Compared with the previous model in which the well is at the center of radial composite gas reservoirs, in this paper we present an obvious “step” after the inner region radial flow regime, which is related to the off-center distance and radius of the inner region. In addition, the effects of some important parameters (such as off-center distance, permeability mobility, inner region radius, and fracture distribution) on typical curves are discussed. Finally, field well testing data are used to verify the accuracy of the model.

Transient modeling of plunger lift with check valve for gas well deliquification in horizontal well

ABSTRACT To improve the plunger gas lift efficiency, a modified plunger was developed by adding a check valve to the downhole positioner in the Changqing Gas Field. However, the transient flow behavior of the plunger lift with check valve is unclear owing to the lack of a reliable method. Therefore, in this study, a simplified transient mechanistic model based on the law of conservation of momentum and mass is proposed to simulate the comprehensive dynamic process of a plunger-lift system. The results of the proposed method exhibited a high coincidence with that of the accumulated gas and liquid production of gas Well-1 in one cycle, and the relative errors were 2.11% and 4.29%, respectively. The calculation results demonstrate that the plunger lift with check valve can effectively prevent the flow of liquid to the bottom of the well, reduce the bottom hole flow pressure, and increase the productivity of gas well during the shut-in period. The efficiency of the plunger lift with check valve was enhanced with an increase in the volume of the accumulated liquid unloaded from the bottom of gas wells. Additionally, for the plunger lift with check valve, the production peak value was higher and the instantaneous gas production peak value was lower in comparison with the conventional plunger. After the plunger reached the wellhead, the instantaneous fluid production of the conventional plunger was relatively unstable than that of the plunger lift with check valve. A certain distance should be maintained from the bottom of the well in the case of the positioner with check valve. If the positioner is placed at the bottom of the tubing, the difference between the lift efficiency of the plunger with check valve and conventional plunger is small, and lower than that of the conventional plunger. The installation position of the downhole positioner in a gas well should be below the accumulated liquids level and should maintain a certain distance between the positioner and bottom of the well (200 m). The results of this study enhance the understanding of the operation mechanism of the plunger lift with check valve, and unloading of the accumulated liquids from the bottom of gas wells.

Transient Coupled Flow Model for Matrix-Fracture in High-Pressure Gas Reservoirs Opened by Gas Drilling

Gas drilling technology is an effective method to protect low permeability tight sandstone reservoirs from damage. However, using this technology to drill high-pressure fractured reservoirs, the fluid flow characteristics are extremely complex, leading to drilling safety challenges. Therefore, based on the conservation equations of mass, momentum, and energy, a new transient coupled flow model in matrix-fracture is established for high-pressure gas reservoirs opened by gas drilling, considering convection term and energy equation, to research the pressure and flow velocity transient behaviors. This model is solved by Shaher Momani’s algorithm and CyabJiBe format, and the type curves of the pressure and flow velocity are plotted. The three flow stages are developed, and the impact of parameters and equation terms on the transient flow behavior is analyzed and discussed, such as the energy equation, the matrix permeability ( k ), the fracture aperture ( L f ), and the fracture outlet pressure. It is found that the energy equation term of the model has a great influence on the transient characteristics such as velocity and pressure, which cannot be ignored. In the first flow stage, the flow velocity characteristics are not affected by the matrix parameters being extremely unstable, but in the second and third stages, the influence of the gas supplied to fracture cannot be ignored. The proposed transient coupled flow model provides a new understanding of the transient flow behavior in matrix-fracture for high-pressure reservoirs during gas drilling, which can be used to interpret the characteristics of pressure and velocity more realistically, to provide support for safe drilling of gas drilling.

Effects of Surge Tank Geometry on the Water Hammer Phenomenon: Numerical Investigation

A surge tank, as one of the most common control facilities, is applied to control head pressure levels in long pressurized pipelines during the water hammer occurrence. The cost-effective operation of surge tanks is highly affected by their characteristics (i.e., surge tank diameter and inlet diameter of surge tanks) and can effectively reduce the repercussion of water hammers. This investigation utilized the method of characteristics (MOC) in order to simulate the behavior of transient flow at the surge tank upstream and the head pressure fluctuations regime for the hydraulic system of a hydropower dam. Firstly, the MOC model was validated by experimental observations. The various types of boundary conditions (i.e., sure tank, reservoir, branch connection of three pipes, series pipes, and downstream valve) were applied to investigate the simultaneous effects of the surge tank properties. In this way, all the simulations of water hammer equations were conducted for nine various combinations of surge tank diameter (D) and inlet diameter of surge tank (d). The results of this study indicated that for the surge tank design with D = 6 m and d = 3.4 m, head pressure fluctuations reached the minimum level in the large section of the pipeline which is the surge tank upstream. Additionally, the occurrence of the water hammer phenomenon was probable in the initial section of the pipeline.

Investigation of shot sleeve distortion and oil cooling in high pressure die casting

It is well known that thermomechanical distortion reduces the service life of shot sleeves in high pressure die casting (HPDC) processes. However, the underlying phenomenon which causes the distortion is still not well characterized. While finite element models (FEM) have been used to analyze shot sleeve distortion, these have typically used simplified 2D representations and do not consider the effect of transient molten metal flow on heat transfer. In the present study, a 3D finite element (FE) model based on ANSYS used a staggered approach to study the sources of shot sleeve distortion and the effect of active oil cooling. Transient flow behavior during pouring, settling, and slow shot phases was simulated using a computational fluid dynamics (CFD) based model after which the temperature field and internal pressure distribution were imported into a structural model which was used to predict shot sleeve distortion at selected instants during a representative steady-state cycle. The simulation results were validated using data obtained from an HPDC machine and demonstrated good agreement. A comparison of large and small internal diameter (ID) shot sleeves showed that the former distort the most and that cooling channels are only moderately effective at minimizing distortion. Based on the complex 3D nature of shot sleeve distortion, the use of total indicator runout (TIR) is also proposed as a metric for minimizing distortion in shot sleeve designs. In addition to distortion, the thermal gradient in the shot sleeve was analyzed and it was noted that the largest source of heat loss is through the mounting flange attached to the HPDC machine frame, which is not an area typically considered for thermal management.

Effect of Nozzle Position on Fluid Flow and Solidification in a Billet Curved Mould using Mould Electromagnetic Stirring

Owing to the smaller cross‐sectional size of the billet, the effect of the position of the submerged entry nozzle (SEN) on the fluid flow in a curved mold is more prominent. The transient fluid flow, heat transfer, and solidification behavior at different nozzle positions and mold electromagnetic stirring (M‐EMS) are investigated using a 3D transient mathematical model. The symmetry index, S, is introduced to quantitatively evaluate the symmetry of the flow field. When the SEN is offset to the outer curve, S is the highest, the flow field mixing is the best, and the liquid level fluctuation is minimal. When the SEN is offset to the inner curve, S is the lowest, and the washing of the solidified shell on the inner curve side is more significant, causing the solidified shell thickness on the inner curve to be thinner, which can easily cause steel breakout accidents. The M‐EMS can improve the uneven flow field caused by the nozzle position. In actual production, the SEN can be appropriately offset to the outer curve, and the application of M‐EMS can improve the flow field distribution of molten steel.

On modelling conjugated heat transfer in the thin slab CC mold and solid shell formation under the applied EMBr

Continuous casting (CC) became one of the dominant steel production technologies throughout last decades. Better quality, energy savings and high production rates are the main aims of the research especially in the field of the thin slab casting (TSC). The electromagnetic brake (EMBr) is applied to control the highly turbulent flow after the fresh melt is fed through the ports of a submerged entry nozzle (SEN). The numerical modelling is a perfect tool to investigate the multiphase phenomena of the turbulent flow in the CC mold, heat transfer and solidification coupled with the effects of the magnetohydrodynamics (MHD). Traditionally the heat transfer in the CC mold during the numerical simulations is predefined by the heat flux profile which could be taken from the plant measurements, published data, or is described by the semi-empirical formulas. In all these cases the heat extraction in the CC mold cavity is strictly predefined and is not significantly influenced by the transient flow behavior. Moreover, the heat flux, used in a simulation, is frequently measured for the different flow pattern inside the mold. That is especially important when the EMBr effects on the solid shell formation are investigated. Thereby, the presented study considers the coupled heat transfer in the water-cooled copper mold, including the averaged thermal resistance between the slab and mold, implemented using OpenFOAM® open-source CFD software. The melt flow, the temperature field, and the induced electric current density are compared between the traditional approach (the applied heat flux) and the modelled heat transfer in the TSC mold. Different scenarios are studied without and with the applied magnetic field.

Dynamic performance of a fluidic diode subjected to periodic flow

This paper presents the dynamic behavior of a fluidic diode (FD) subjected to periodic flow (oscillatory flow). This study captures the transient performance of the FD, which a steady-state flow analysis cannot predict, helping in better prediction of the performance and in designing an efficient model for the real sea flow profile. The FD offers variable resistance to the flow depending on its geometrical shape. Its performance is given by diodicity, which is a ratio of pressure drop in reverse to forward flow. It is used with the turbine to improve flow rectification. The numerical model is solved for three-dimensional unsteady Reynolds-Averaged Navier Stokes equations using ANSYS Fluent 16.1. The article presents the FD's detailed transient flow behavior and performance with the turbine. The FD operating in oscillatory flow performed better than in a steady flow because of the dynamic nature of the fluid. The analytical study shows that the performance of FD with turbine performed better at lower flow-coefficient.

Effect of Swirling Flow Nozzle on Fluid Flow and Solidification in a Round Bloom Continuous Casting Mold

The nozzle structure has an important effect on the fluid flow in the mold, which can significantly improve the solidified shell and product quality of alloy steel round bloom. The transient fluid flow, heat transfer, and solidification behavior under different nozzle structures and mold electromagnetic stirring (M-EMS) are investigated using a 3D transient mathematical model. The results show that a third small recirculation zone appears near the meniscus after the application of the swirling flow nozzle (SFN). The impact depth of SFN is shallower than that of the original submerged entry nozzle (SEN) impact, and the lower circulation zone is shifted upward. The horizontal swirling flow generated by SFN can significantly weaken the washing of the initial shell by high-temperature steel and improve the uneven growth phenomenon of the inner and outer curved solidified shell caused by mold curvature. The swirling flow produced by M-EMS in the mold can also improve the washing of the initial shell by the high-temperature jet and the uneven growth of the inner and outer curved shell. M-EMS can expand the high-temperature zone in the upper part of the mold, promote the superheat dissipation of the molten steel, and promote the growth of the solidified shell. In addition, after the application of M-EMS, the tangential velocity of -15° SFN in the meniscus is smaller, and the resulting liquid level fluctuation is lower at 5.07 mm, which is less likely to produce slag entrapment and is conducive to improving the quality of round bloom.

Evaluation of groundwater flow through a high rockfill dam foundation in karst area in response to reservoir impoundment

Constructing high dams in karst valleys remains a challenging issue as karst conduits provide preferential channels for flow through the foundations. The uncertainty of the karst system drastically increases the risk of leakage and hence the difficulty in seepage control at the foundations. This study examined the transient flow behaviors through a karst foundation on which a rockfill dam with a height of 219 m had been constructed. During reservoir filling, an abnormal pressure rise occurred in the foundation downstream the grout curtains, typically with a magnitude of 53∼69 m higher than the pore pressure head at the neighboring positions. This phenomenon was comprehensively investigated by site characterization, inverse modelling, numerical simulation and cross-correlation analysis, demonstrating that the abnormal pressure rise is locally induced by eroded fault (left bank) or contact zones between karst formations (right bank). These conduits have an effective permeability value one order of magnitude higher than that of the karst formations, which quickly transmit the reservoir pressure pulse across the grout curtains, as evidenced by a higher cross-correlation and a smaller lag between pool level and piezometer measurements. The grout curtains have sufficiently low permeability in limiting the amount of leakage through the foundation, and hence ensure the safety of the reservoir operation in spite of the pressure rise. This study confirms the applicability of the equivalent continuum model in addressing groundwater flow problems in karst formations, as long as the site conditions are properly characterized.

Transient natural convective heat transfer and fluid flow in an undulated cavity: Effects of localized heat sources

AbstractThe purpose of this research work is to investigate two‐dimensional transient natural convective heat transfer and fluid flows in an undulated cavity by placing solid objects with isolated heated surfaces on the bottom wall. We discretize the coupled nonlinear transport equations using a higher‐order compact finite‐difference scheme. First, we test our scheme using existing experimental and numerical data. Then, we analyze the transient and steady‐state natural convective flow phenomena for distributed heat sources on corrugations on the lower wall for a range of the Rayleigh number and Prandtl number . These simulated outcomes are presented in the form of central‐line velocity , local and averaged Nusselt numbers, streamlines , dispersion of isotherms , and so forth. It is found that the transient fluid flow behavior is more magnificent than the steady‐state solutions and shows the dominant behavior of the prominent primary cells over secondary cells, where it influences the heat transfer rates inside the entire enclosure. In steady states, at high Rayleigh numbers; convection dominates, formation of thermal boundary layers, compression of isotherms, and stratification of isotherms are significantly observed. Our results show many interesting flow phenomena that have not been analyzed previously.

Mean Flow, Turbulent Structures, and SPOD Analysis of Thermal Mixing in a T-Junction with Variation of the Inlet Flow Profile

This paper investigates the effects of different inlet flow profiles on thermal mixing within a T-junction using CFD simulations with the IDDES-SST turbulence model. The different combinations of inlet flow profiles are related to different stage in the flow entry region. The effects of the inlet flow profile on the mean and transient flow behaviour are assessed, while a spectral proper orthogonal decomposition and power spectral density analysis are performed to assess the underlying flow structures and the predominant frequency modes. It is found that the vortical structures associated with the horseshoe and hovering vortex systems consist of a single roll-up vortex for cases with uniformly distributed boundary conditions (BCs) at the branch inlet whereas a double roll-up vortex is observed for the other cases. The double roll-up vortex enhances the mixing locally due to the entrainment of fluid from the branch pipe in these vortical structures, which then results in a lower mean temperature distribution. The appearance of the secondary vortex pair and the nested vortices is delayed for cases with uniformly distributed BCs at the branch inlet, which again results in lower thermal mixing and consequently higher values of mean temperature when compared with the other cases. It is also found that the vorticity related to the counter-rotating vortex pair as well as to the second pair of vortices rotating in the opposite direction is higher for cases with uniformly distributed BCs at the branch inlet. Lastly, the combinations of inlet flow profiles lead to different coherent structures, and the dominant frequencies are of a Strouhal number of around 0.7 for uniformly distributed profiles at the branch inlet and in the range 0.4–0.5 for the other cases.

Modeling the Transient Flow Behavior of Multi-Stage Fractured Horizontal Wells in the Inter-Salt Shale Oil Reservoir, Considering Stress Sensitivity

Oil flow in inter-salt shale oil reservoirs is different from that of other oil fields due to its high salt content. Dissolution and diffusion occur when the salt minerals meet the water-based working fluid, resulting in drastic changes in the shale’s permeability. In addition, ignoring the stress-sensitive effect will cause significant errors in naturally fractured reservoirs for a large number of the natural fractures developed in shales. This study presents a transient pressure behavior model for a multi-stage fractured horizontal well (MFHW) in inter-salt shale oil reservoirs, considering the dissolution of salt and the stress sensitivity mentioned above. The analytical solution of our model was obtained by applying the methods of Pedrosa’s linearization, the perturbation technique and Laplace transformation. The transient pressure of a multi-stage fractured horizontal well in an inter-salt shale oil reservoir was obtained in real space by using the method of Stehfest’s numerical inversion. The bi-logarithmic-type curves thus obtained reflected the characteristics of the transient pressure behavior of a MFHW for the inter-salt shale oil reservoirs, and eight flow periods were recognized in the type curves. The effects of salt dissolution, stress sensitivity, the storativity ratio and other parameters on the type curves were analyzed thoroughly, which is of great significance for understanding the transient flow behavior of inter-salt shale oil reservoirs.

Effectiveness of splitter plate to control fluid forces on a circular obstacle in a transient flow: FEM computations

The reliability of the usage of a splitter plate (passive control device) downstream of the obstacle, in suppressing the fluid forces on a circular obstacle of diameter D = 0.1;;{text{m}} is studied in this paper. The first parameter of the current study is the attachment of a splitter plate of various lengths (L_{i} ) with the obstacle, whereas the gap separation (G_{i} ) between the splitter plate and the obstacle, is used as a second parameter. The control elements of the first and second parameters are varied from 0.1 to 0.3. For the attached splitter plates of lengths 0.2 and 0.3, the oscillatory behavior of transient flow at Re = 100 is successfully controlled. For the gap separation, 0.1 and 0.2 similar results are obtained. However, it is observed that a splitter plate of too short length and a plate located at the inappropriate gap from the obstacle, are worthless. A computational strategy based on the finite element method is utilized due to the complicated representative equations. For a clear physical depiction of the problem, velocity and pressure plots have been provided. Drag and lift coefficients the hydrodynamic benchmark values are also evaluated in a graphical representation surrounding the obstacle’s peripheral surface as well as the splitter plate. In a conclusion, a splitter plate can function to control fluid forces whether it is attached or detached, based on plate length and gap separation between obstacle and plate, respectively.

Transient CFD Modelling of Air–Water Two-Phase Annular Flow Characteristics in a Small Horizontal Circular Pipe

The liquid film formed around the inner walls of a small horizontal circular pipe often exhibits non-uniform distributions circumferentially, where the film is thinner at the top surface than the bottom one. Even with this known phenomenon, the problem remains a challenging task for Computational Fluid Dynamics (CFD) to predict the liquid film formation on the pipe walls, mainly due to inaccurate two-phase flow models that can induce an undesirable ‘dry-out’ phenomenon. Therefore, in this study, a user-defined function subroutine (ANNULAR-UDF) is developed and applied for CFD modelling of an 8.8 mm diameter horizontal pipe, in order to capture transient flow behaviour, flow pattern formation and evolving process and other characteristics in validation against experiments. It is found that CFD modelling is able to capture the liquid phase friction pressure drop about maximum of 30% in deviation, consistent to the correlated experimental data by applying an empirical correlation of Chisholm. Due to the gravity effect, the liquid film is generally thicker at the bottom wall than at the top wall and this trend can be further enhanced by increasing the superficial air–water velocity ratios. These findings could be valuable for HVAC industry applications, where some desirable annular flow features are necessary to retain to achieve high efficiency of heat transfer performance.

Analysis on annular flow of liquid transported through a partially filled axially rotating pipe

In rotary tube reactors, rotary evaporators, or rotary atomizers, liquid is transported through a partially filled axially rotating pipe. The flow is annular when the pipe rotation is fast enough, as in most engineering applications; in this research, we investigated the steady and transient behavior of annular flows in a partially filled axially rotating pipe. First, the governing equations of a laminar annular flow were derived, solved, and verified. Then, the theory was used to study the transient flow behavior. The responses of the outlet flowrate to inlet flowrate variations and pressure fluctuations were investigated. To clarify the system parameters in which the theory holds, we also conducted experiments to find flow mode boundaries between the non-annular flow and the annular flow. Steady state solutions of the theory were then used to find system parameters in which the flow is laminar. The effects that a screw inserted inside the pipe has, on both the flow mode boundaries and the transient flow characteristics, are also demonstrated. To the best of our knowledge, this is the first inspection of the transient characteristics of an annular flow and the effects of an inserted screw on this type of flow.

Semi-Analytical Modeling of Geological Features Based Heterogeneous Reservoirs Using the Boundary Element Method

The objective of this work is to innovatively apply the boundary element method (BEM) as a general modeling strategy to deal with complicated reservoir modeling problems, especially those related to reservoir heterogeneity and fracture systems, which are common challenges encountered in the practice of reservoir engineering. The transient flow behaviors of reservoirs containing multi-scale heterogeneities enclosed by arbitrarily shaped boundaries are modeled by applying BEM. We demonstrate that a BEM-based simulation strategy is capable of modeling complex heterogeneous reservoirs with robust solutions. The technology is beneficial in making the best use of geological modeling information. The governing differential operator of fluid flow within any locally homogeneous domain is solved along its boundary. The discretization of a reservoir system is only made on the corresponding boundaries, which is advantageous in closely conforming to the reservoir’s geological description and in facilitating the numerical simulation and computational efforts because no gridding within the flow domain is needed. Theoretical solutions, in terms of pressure and flow rate responses, are validated and exemplified for various reservoir–well systems, including naturally fractured reservoirs with either non-crossing fractures or crossing fractures; fully compartmentalized reservoirs; and multi-stage, fractured, horizontal wells with locally stimulated reservoir volumes (SRVs) around each stage of the fracture, etc. A challenging case study for a complicated fracture network system is examined. This work demonstrates the significance of adapting the BEM strategy for reservoir simulation due to its flexibility in modeling reservoir heterogeneity, analytical solution accuracy, and high computing efficiency, in reducing the technical gap between reservoir engineering practice and simulation capacity.

Effects of rolling motion on transient flow behaviors of gas-liquid two-phase flow in horizontal pipes

The investigation of transient flow behaviors of gas-liquid two-phase flow under ocean conditions is vital to the application of gas-liquid transport in ocean engineering area. In this paper, the gas-liquid two-phase flow numerical model of rolling horizontal pipe is established based on CFD code combined with user-defined functions (UDF). The three-dimensional rolling flow fields are simulated using the volume of fluid (VOF) model, RNG k−ε turbulence model and additional inertia force method. First, the simulation results are compared with the experimental data, which revealed a reasonable agreement. Then, the variation in transient flow behaviors by horizontal pipe (L = 2.0 m, D = 0.035 m) with varying rolling conditions (θm = 2°-6°, T = 0.5–4.0 s) and flow velocities (jG = 0.1–10.0 m/s, jL = 0.1–0.5 m/s) are investigated. The results showed that the rolling motion caused agglomeration of dispersed bubbles and gas slugs into a continuous gas column, increased the cross-sectional void fraction significantly. The variation of additional inertial force and pressure drop increased with the increase of rolling angle and the decrease of the rolling period. Compared with the rolling angle, the transient flow behaviors are more sensitive to the rolling period. In addition, as the initial gas volume fraction increased, the effects of rolling motion on the transient flow behaviors decreased gradually. These qualitative conclusions may serve as a reference for gas-liquid transport simulations under rolling conditions.