Main Flow Patterns Research Articles

Thermal hydraulic behavior of a large dimension hybrid heat pipe/oscillating heat pipe

Similar to the layout of an oscillating heat pipe (OHP), a quartz hybrid heat pipe (HHP) with an inner diameter of 5 mm, exceeding 59.7 % of the capillary threshold of OHP, was designed. The detailed thermal hydraulic behavior of fluid in the HHP has been revealed. It was found that the HHP undergoes a heat transfer mode transition from phase change to pulsating flow. It is also means that the liquid slugs can be dynamically and stably formed if the heat input is sufficient. The single bubble growth and the multi-bubble coalescence are two ways to form the intermittent flow. In addition, as the main flow pattern in low filling ratio (FR), the formation of annular flow is closely concerned in the behaviors of fluid. Moreover, the higher the FR is, the clearer the contour of slug flow is. At the same time, the oscillating motion can be formed easily at a high FR, resulting in a better performance of HHP in lower heat load. However, as the heat input increases, HHP with a 60 % filling ratio exhibits lower thermal resistance, achieving a minimum value of 0.08 °C/W at 100 W.

Study on the Flow Characteristics of Heavy Oil-Water Two-Phase Flow in the Horizontal Pipeline.

Aiming at the problem of transportation for heavy oil during the middle-later development stages of the Lvda oilfield, based on the self-developed design of a visual circulating flow experimental apparatus for heavy oil-water two-phase flow-the flow regime characteristics and corresponding drag properties of the two-phase flow of Lvda viscous oil, which is simulated by 500# industrial white oil and water in a horizontal pipeline are investigated experimentally. According to the Kelvin-Helmholtz instability theory, the flow pattern transition criteria from stratified flow to annular flow (AF) are proposed. The effects of 0.11-0.90 m/s oil superficial velocities, 0.06-1.49 m/s water superficial velocities, and 0.09-0.93 input water cuts on the drag reduction effect of different flow regimes are analyzed. The experimental results indicated that with the increase of mixing velocity and water volume fraction, stratified flow, AF, oil plug flow, and dispersed oil lump flow are successively observed in the horizontal heavy oil-water two-phase flow, in which AF is the main flow pattern. As the Froude number increases to 4.0, the input water volume fraction does not change any more and remains at about 10% of the total flow rate in the process of converting from stratified flow to AF. The four delivery approaches can archive the reduction of transportation resistance for heavy oil at different degrees, in which the transportation of heavy oil surrounded by a water ring has the best effect of drag reduction. At the optimal working conditions of 0.61 m/s oil superficial velocity, 0.07 m/s water superficial velocity, and 0.10 input water cut, the pressure drop of water annulus conveying for heavy oil is only 1/62.54 of that of separate transport for pure heavy oil under the same oil flow rate.

Numerical Calculation of Gas–Liquid Two-Phase Flow in Tesla Valve

In this paper, the gas–liquid two-phase flow within a Tesla valve under zero-gravity conditions is numerically studied. Based on the VOF model and the inlet two-phase separation method, the forward and reverse flow patterns and pressure drop changes in a Tesla valve at different inlet velocities were analyzed. At an inlet velocity of 0.1–0.2 m/s, the flow pattern was slug flow, the bubbles were evenly distributed in different positions in the Tesla valve, and the velocity difference between the main pipe and the arc branch pipe was small. When the inlet velocity was 0.4 m/s, the main flow pattern was annular flow, and there was a phenomenon of gas–liquid phase separation through different flow channels, which was related to centrifugal force. At an inlet velocity of 0.6–0.8 m/s, bubbly flow and slug flow coexisted, which was related to the uneven velocity. In the study range, the difference in the forward and reverse pressure drops of two-phase flow was smaller than that of single-phase flow, and the two-phase diodicity decreased first and then increased with the change in inlet velocity, reaching minimum values of 0.78 at 0.2 m/s and 1.44 at 0.8 m/s.

Study on the Transient Flow Characteristics of a Hump Water Pipeline Based on the Random Distribution of Bubbles

Aiming at establishing the transient flow characteristics of gas–liquid two-phase flow in high-undulation water pipelines, based on the bubble distribution law measured using physical tests, the bubble distribution law function was input into the hump-pipe fluid domain model, and CFD numerical simulation was carried out for different flow rates and different air contents. The CLSVOF two-phase flow model and the RNG k-ε turbulence model were used to analyze the flow pattern evolution and pressure pulsation propagation in the process of gas–liquid two-phase flow through a hump pipe. The results show that the bubble size has a lognormal distribution, the equivalent diameter is between 3 mm and 10 mm, and the evolution of the flow pattern in the hump pipe is complex and violent. In the horizontal pipe section, there are three main flow patterns: bubble flow, wavy flow and segment plug flow. In the vertical pipe, there are two main flow patterns, slug flow and churning flow, and the flow pattern is affected by the flow rate and the air content rate. When air bubbles or air pockets in the pipeline flow through a certain area, this leads to a steep increase and decrease in the pressure pulsation amplitude in the region, and the pressure fluctuation is extremely frequent. Compared with the water flow rate, the air content is the main factor affecting the relative pressure pulsation amplitude under the condition of a 0.15-air content operating mode, which is generally approximately two to six times that of the 0-air content operating mode. The results of the research should facilitate the prediction of stagnant gas pipeline system bursts and water hammer protection, providing a theoretical basis and calculation parameters.

Modelling secondary circulations in stratified bi-directional flows: A potential mechanism for flux transfer from lower to upper fluid layers

Results are presented for new laboratory-scale numerical simulations of bi-directional stratified flows generated within an idealized trapezoidal sill-channel topography, focussing on the lateral (or secondary) flow structure across the channel both in non-rotating and rotating frames of reference. The simulations utilise the non-hydrostatic Bergen Ocean Model (BOM), a three-dimensional general ocean circulation model. The results from the BOM simulations are verified by large-scale experimental data obtained in the LEGI Coriolis rotating platform in Grenoble, within which velocity and density fields for bi-directional stratified flows were measured through particle image velocimetry (PIV) and micro-conductivity density probes, respectively. The BOM simulations reproduce the main dynamic flow patterns and structure of the large-scale exchange flows generated through the trapezoidal sill-channel, with the lower layer saline intrusion flux shown to reduce, due to partial blockage, as the upper freshwater flow is increased (i.e. net barotropic forcing). Non-rotational BOM simulations show upward (and downward) flow along the centreline of the trapezoidal sill-channel in the upper (and lower) layers, with symmetrical counter-rotating circulation cells forming both above and below the density interface. By contrast, equivalent BOM simulations within a rotating frame of reference show the secondary flow circulation in the lower dense water layer to be dominated by Ekman dynamics, while two co-rotating cells are formed in the upper freshwater layer above the inclined density interface. In these rotational cases, significant upward and downward velocities (i.e. strong upwelling and downwelling) are generated adjacent to the inclined sill-channel side walls (in comparison to non-rotating cases). This secondary flow effect may be especially relevant for exchange flows in estuaries, fjords, deep-ocean channels and sea straits, where the channel width exceeds the Rossby radius of deformation and, thus, Earth rotation effects become important dynamically. In particular, any potential vertical transport pathway associated with this upwelling and downwelling at the inclined channel side slopes may have strong managerial implications in coastal areas, whereby tracers (e.g. contaminants, salinity, reduced DO waters, fine sediments) can be transferred from deep waters to the near surface.

Investigation on the influence of bucket’s flow patterns on energy conversion characteristics of Pelton turbine

Efficient energy conversion can improve Pelton turbine unit efficiency and bring higher economic benefits. However, the reasons that influence the energy conversion characteristics of the Pelton turbine have not been effectively revealed. The main reason is the lack of systematic research on the change process of flow patterns in the bucket and its relationship with the energy conversion characteristics. Experimental and numerical simulation studies of a Pelton turbine were conducted. The change process of the flow patterns from when the jet enters the bucket to when it is completely discharged is analyzed and three main flow patterns in the buckets are summarized. Through energy characteristic analysis, it was found that during the power change process of the bucket, the flow rate entering the bucket and the velocity moment at the inlet of the bucket shows a trend of first increasing and then decreasing, while the velocity moment at the outlet of the bucket and flow loss show an opposite trend, resulting in the most sufficient energy conversion when the jet is perpendicular to the bucket. The basic topology of the bucket energy conversion process is constructed to effectively understand the Pelton turbine's energy conversion characteristics.

Numerical and Experimental Study on the Process of Filling Water in Pressurized Water Pipeline

As an important working condition in water conveyance projects, the water filling process of pipelines is a complex hydraulic transition process involving water–air two-phase flow with sharp pressure changes that can easily cause pipeline damage. In light of the complex water–air two-phase flow during pipeline water filling, this study explores the water filling process of right-angle elbow pressure pipelines using CFD numerical simulations and physical model experiments, analyzing changes in water phase volume fraction, water-gas two-phase flow patterns, and hydraulic parameters in the pipeline under low flow rate conditions of 0.6 m/s and high flow rate conditions of 1.5 m/s. Results show that under low flow rate conditions, there is more local trapped gas at the top of the pipeline, causing negative pressure at local high points in the pipeline and forming a vacuum. Under high velocity conditions, water-gas two-phase flow changes more frequently in the pipeline, with a large number of bubbles collapsing at the top, resulting in large fluctuations in pipeline pressure. Finally, through physical experiments, the main flow patterns during water filling in right-angle elbows are verified and analyzed. These results have certain reference significance for formulating safe and efficient water filling velocity schemes for pressurized pipelines.

Improvement of hemodynamics in mesenteric microcirculation in septic shock rats by anisodamine and anisodine

Anisodamine and anisodine have been used in treatment of septic shock, but the underlying mechanism are still unclear. In the present study, the effects of anisodamine hydrobromide (Ani HBr) and anisodine hydrobromide (AT3) on the mesenteric hemodynamics in septic shock rats were performed. The rat model of septic shock was established by intravenous tail vein injection of 5 ​mg/kg lipopolysaccharide (LPS), and then treated with Ani HBr, AT3, racemic anisodine (Race Ani) or atropine (ATP). The mesenteric microcirculation was observed using the intravital microscopy. Then, the flow pattern of the microcirculation, leukocytes dynamics and the plasma levels of cytokines tumor necrosis factor (TNF)-α and interleukin-6 (IL-6) were analyzed. Compared with the control rats, reduced mean arterial pressure, increased heart rate, and slow microcirculatory blood flow was found in septic shock rats. The main abnormal flow patterns were intermittent and reciprocating motions. Ani HBr, AT3, Race Ani and ATP elevated the mean arterial pressure and reduced heart rate in septic shock rats. Ani HBr and AT3 not only restored the velocity of microcirculatory blood flow and improved the microcirculatory flow patterns, but also suppressed the LPS-induced leukocyte-endothelium interaction and releases of TNF-α and IL-6. Therefore, Ani HBr and AT3 improves hemodynamics in both macro- and microcirculation, which provide a novel experimental basis for exploring the mechanobiological mechanisms in septic shock.

Numerical Investigation of the Optimum Angle for Open Channel Junction

Numerous natural and artificial streams, including those for irrigation ditches, wastewater treatment facilities, and conveyance structures for fish movement, have open channel confluences. The flow dynamics at and around the junction are intricate; in particular, immediately downstream of the junction, the flow creates a zone of separation on the inner wall along with secondary recirculation patterns. The structure of this complicated flow depends on several factors, including the flow rates in both channels, the angle of confluence, the geometry of the channels, including the longitudinal slope and bed discordance, the roughness of the boundary, and the intensity of the turbulence. It also has a significant impact on bed erosion, bank scouring, etc. The objective of the current work is to calculate the velocity profile and the separation zone dimensions for four angles (30o, 45o, 60o, and 75o) through the simulation process, and the best angle using a three-dimensional model. This work gives a detailed application of the numerical solution (Finite Volume) via Flow 3D software. Results for two flow discharge ratios, q*=0.250 and q*=0.750 were shown; the numerical model and the experimental results agreed well. The findings are consistent with past research and demonstrate how the main channel flow pattern is affected by changes in the channel crossing angle, as well as how greater separation zones are produced in the main channel when the flow discharge ratio q* (main channel flow divided by total flow) is smaller. Analysis revealed that the separation zone's smallest diameter will be at the 75ocrossing angle. Doi: 10.28991/CEJ-2023-09-05-07 Full Text: PDF

Numerical investigation on the formation of the re-entrant flow and the transformation of varying shedding modes in cloud cavitation

The objective of this paper is to investigate two types of cloud shedding processes around the NACA66 (mod) hydrofoil with emphasis on the formation of the re-entrant flows and the transformation of varying shedding modes. The LES method combines the Schnerr-Sauer cavitation model in OpenFOAM to capture the detailed flow structures. Combining the experimental observation, the cloud shedding process can be divided into main re-entrant flow mode, transition mode, and side re-entrant flow mode. The re-entrant flow is primed from the middle of the attached cavity closure for the main re-entrant flow pattern. The velocity is more stable as it develops in a fan shape towards the leading edge of the hydrofoil. For the side re-entrant flow mode, the rotation and local collapse of cloud cavity in the previous cycle resulted in the incipient of the side re-entrant flow. Compared with the main re-entrant flow, the velocity of the side re-entrant flow fluctuates more significantly. The transition between the side re-entrant flow mode and the main re-entrant flow mode can be characterized by the normalized cavity length (lmax/c) and the cavity shedding frequency (St number).

Liquid–liquid two-phase flow in a wire-embedded concentric microchannel: Flow pattern and mass transfer performance

In this work, flow pattern and mass transfer of liquid–liquid two-phase flow in a wire-embedded concentric microchannel are studied using toluene–water system. Droplet flow, slug flow, oval flow and annular flow are observed in the wire-embedded concentric microchannel. The effects of embedded wires and physical properties on flow patterns are investigated. The embedded wire insert is conducive to the formation of annular flow. The flow pattern distribution regions are distinguished by the Caaq (capillary number)–Weorg (Weber number) flow pattern map. When Weorg＜0.001, slug flow is the main flow pattern, and when Weorg＞0.1, annular flow is the main flow pattern. Oval flow and droplet flow are between Weorg=0.001–0.1, and oval flow is transformed into droplet flow with the increase of Caaq. The effect of flow rate, phase ratio, initial acetic acid concentration, insert shape and flow patterns on mass transfers are studied. Mass transfer process is enhanced under annular flow conditions, the volumetric mass transfer coefficient is up to 0.36 s–1 because of the high interfacial area and interface renewal rate of annular flow.

Comparison of mixing mechanism under different rotating directions in a horizontal self-cleaning differential rotating twin-shaft kneader

Finite element method (FEM) simulation combined with the mesh superposition technique (MST) was adopted to investigate the flow field in a horizontal self-cleaning differential rotating twin-shaft kneader with a highly viscous Newtonian fluid. The distributive mixing process and mixing efficiency were investigated by using the particle tracking technique. The comparison of flow pattern, distributive mixing process and mixing efficiency for the opposite-rotating, co-rotating and back-rotating twin-shaft kneader was performed. For the opposite-rotating kneader, the material flow in the left and right region merges in the upper region of overlapping zone, moves towards the lower region and is split into two parts in the lower region of overlapping zone. For the co-rotating kneader, the main flow pattern that the material moves towards the right region from the left region. Besides, there exists the secondary flow and periodic cyclic vortex in the overlapping zone. For the back-rotating kneader, the material flow in the left and right region merges in the lower region of overlapping zone, moves towards the upper region and is split into two parts in the upper region of overlapping zone. The material exchange between the left and right part of flow domain in the co-rotating kneader is much more efficient than that in the opposite-rotating and back-rotating kneader. The mean length of stretch, instantaneous mixing efficiency and time averaged mixing efficiency of opposite-rotating kneader is very close to that of back-rotating kneader, which is much smaller than that of co-rotating kneader. Hence, the co-rotating kneader possesses much better mixing performance than the opposite-rotating and back-rotating kneaders.

Heat Transfer of Water Flow Boiling in Nanostructured Open Microchannels

In recent years, the open microchannel has drawn increasing interest, but severe local dryout limited the heat transfer capability of flow boiling. It was anticipated that nanostructures with exceptional capillary wicking abilities would overcome this problem. In this study, blade-like CuO nanostructures were created in the copper open microchannels to experimentally investigate water flow boiling. Experiments were carried out in nanostructured open microchannels (NMCs), and smooth-surface open microchannels (SMCs), as a comparison, were examined under identical operating conditions. Four main flow patterns, including bubbly flow, slug flow, and two kinds of stratified flow, dominated successively in NMCs and SMCs. Although the flow patterns were similar in NMCs and SMCs, the heat transfer coefficient (HTC) of flow boiling was greatly enhanced by nanostructures under conditions of medium and high heat flux, while the nanostructures’ influence on HTC was unnoticeable at low heat flux. At medium and high heat fluxes, the dependence of HTC on heat flux and flow rate indicated the joint contribution of nucleate boiling mechanism and convective evaporation mechanism to heat transfer. The enhanced effect of nanostructures on nucleate boiling and convective evaporation became more prominent as heat flux increased, leading to a higher HTC in NMCs than in SMCs at higher heat flux conditions.

A flow map for core/shell microdroplet formation in the co-flow Microchannel using ternary phase-field numerical model

Core/shell microdroplets formation with uniform size is investigated numerically in the co-flow microchannel. The interface and volume fraction contour between three immiscible fluids are captured using a ternary phase-field model. Previous research has shown that the effective parameters of microdroplet size are the physical properties and velocity of the three phases. By adjusting these variables, five main flow patterns are observed in numerical simulations. A core/shell dripping/slug regime is observed when the inertia of the continuous phase breaks the flow of the core and shell phases and makes a droplet. In the slug regime, the continuous phase has less inertia, and the droplets that form are surrounded by the channel walls, while in the dripping regime, the shell phase fluid is surrounded by the continuous phase. An increase in continuous-fluid or shell-fluid flow rate leads to dripping to a jetting transition. When three immiscible liquids flow continuously and parallel to one another without dispersing, this is known as laminar flow. In the tubing regime, the core phase flows continuously in the channel's central region, the shell phase flows in the annulus formed by the core phase's central region, and the continuous phase flows between the shell phase fluid and channel walls. In order to discriminate between the aforementioned flow patterns using Weber and Capillary numbers and establish regime transition criteria based on these two dimensionless variables, a flow regime map is provided. Finally, a correlation for shell thickness using shell-to-core phase velocity ratio and conducting 51 CFD simulations was proposed.

Multi-scale proper orthogonal decomposition analysis of instabilities in swirled and stratified flames

This study examines the flow field dynamics of bluff-body stabilized swirling and non-swirling flames produced from the Cambridge/Sandia Stratified Swirl Burner. This burner has been used in previous studies as a benchmark for high-resolution scalar and velocity measurements and for validating numerical models. The burner was designed to create reacting flow conditions that are representative of turbulent flows in modern combustion systems, including sufficiently high turbulence levels, and to operate under both premixed and stratified conditions. High-speed stereoscopic particle image velocimetry was used to acquire time-resolved velocity data for a series of turbulent methane/air flames at both premixed and stratified conditions. We employ the multi-scale proper orthogonal decomposition (mPOD) to identify the main flow patterns in the velocity field and isolate coherent structures linked to various flow instabilities. The results show that the most energetic structures in the flow are consistent with the Bénard–von Kármán (BVK) instability due to the presence of the bluff-body and the Kelvin–Helmholtz (KH) instability caused by the shear layer between the inner and the outer flow. In both the swirling and non-swirling cases, the BVK is suppressed by the combustion, except for the most stratified swirling case. Moreover, the results show that combustion does not affect the KH instability because the shear layer does not coincide with the flame position.

Optimal position of air purifiers in elevator cabins for the improvement of their ventilation effectiveness

Ventilation in confined spaces is essential to reduce the airborne transmission of viruses responsible for respiratory diseases such as COVID-19. Mechanical ventilation using purifiers is an interesting solution for elevator cabins to reduce the risk of infection and improve the air quality. In this work, the optimal position and blowing direction of these devices to maximize ventilation and minimize the residence time of the air inside two cabins (large and small) is studied. Special attention is devoted to idle periods when the cabin is not used by the passengers, in order to keep the cabin ambient safe and clean, avoiding that the trapped air in the cabin (after its use) could suppose a reservoir for contaminants. CFD numerical models of two typical cabin geometries, including the discretization of small slots and grilles for infiltration, have been developed. A full 3D URANS approach with a k-epsilon RNG turbulence model and a non-reactive scalar to compute the mean age of air (MAA) was employed. The CFD results have been also validated with experimental measurements from a home-made 1:4 small-scale mock-up. The optimal position of the purifier is on the larger sidewall of the cabins for a downward blowing direction (case 1 of the database). Flow rates in the range of 0.4–0.6 m3/min, depending on the size of the cabin, are sufficient to assure a correct ventilation. Upward blowing may be preferable only if interaction of the jet core with the ceiling or other flow deflecting elements are found. In general, the contribution of infiltrations (reaching values of up to 10%), and how these secondary flows interact with the main flow pattern driven by the purifier, is relevant and not considered previously in the literature. Though an optimal position can improve ventilation considerably, it has been proven that a good choice of the purification flow rate is more critical to ensure an adequate air renewal.

Flow patterns of ionic liquid based aqueous biphasic systems in small channels

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by the addition in water of a hydrophilic ionic liquid (1-Butyl-3-methylimidazolium Chloride, C4mimCl) and a kosmotropic salt (tripotassium phosphate, K3PO4). The flow patterns of IL-ABS were studied in capillary channels with 0.2, 0.5 and 0.8 mm internal diameter; this is the first time such two-phase flows have been investigated. Three weight concentrations of the ionic liquid and the salt (18, 20 and 22 wt%) were chosen within the biphasic region. The main flow patterns included plug, dispersed and parallel flow. It was found that both channel diameter and weight concentrations would affect the flow patterns observed. Finally, a generalized flow pattern map was plotted using a combination of capillary and Reynolds numbers, where the transition boundaries of plug flow collapsed for all ionic liquid and salt concentrations studied.

Improved Calculation Method for Siphon Drainage with Extended Horizontal Sections

Slope siphon drainage is a convenient and efficient above-ground drainage method that is free of manual power and can effectively maintain the stability of potential landslides and prevent the loss of life and property. The complex engineering topography inevitably requires the use of siphon drains with a total length of more than 150 m and a horizontal section length of more than 80 m, which significantly increases the difficulty of calculating the drainage capacity and thus affects the actual utilization of the project. The traditional siphon flow rate equation does not apply to long-pipe siphon conditions, especially when the lift is close to the limit, and there are significant errors in the calculation results, for which we propose a new calculation method. The proposed method considers both air release and flow-pattern classification. Thirty-six sets of experiments were conducted to validate our proposed calculation method. The results showed that our method not only calculated the siphon flow velocity well but also predicted the main flow pattern in the siphon in the experiment well. Furthermore, the equation for calculating the siphon flow velocity was extended to the siphon operation mode with long horizontal sections.

Study on Flow Model and Flow Equation of Shale Gas Based on Microflow Mechanism

Shale gas storage and permeability space is between nanometers and micrometers and has strong multiscale characteristics, resulting in highly complicated shale gas flow. Therefore, the development of shale gas needs to clarify the seepage mechanism of shale gas and establish a flow model and flow equation that can analyze shale gas flow. In this paper, based on the single nanotube model, combined with the Weiyuan-Changning shale gas demonstration zone of the target layer of the Longmaxi formation shale core high-pressure mercury pore throat test results, the contribution of seepage, diffusion, transition flow, and free molecular flow to shale gas flow was calculated. The contribution of seepage and diffusion is over 95%, and seepage and diffusion are the main flow pattern. Then, a shale gas seepage and diffusion coupled flow model and coupled flow equation were established. A method for calculating shale permeability and diffusion was proposed using the relationship between flow pressure and shale gas velocity. Finally, shale gas flow experiment analysis was carried out to verify that the established shale gas flow model and flow equation can describe the shale gas flow well. The result shows that the flow rate of shale gas is composed of seepage flow rate and diffusion flow rate. The seepage flow rate is proportional to the pseudopressure difference and proportionate to the low-pressure squared difference. The diffusion velocity is proportional to the difference in shale gas density, and the pressure difference in low pressure is proportional. As the pressure of a shale gas reservoir decreases, the proportion of diffusion flow increases. The research results enrich the understanding of shale gas flow; it also has particular reference significance to the development of shale gas reservoirs.

Numerical Simulation of the Flow Pattern of Spiral Annular Flow with a Guide Strip by Spiral On-Way.

To study the gas–liquid two-phase spiral annular flow pattern and its conversion law in a horizontal tube with twist tape by spiral on-way, a numerical simulation is carried out using the RNG k-ε model, and the DPM model is adopted as the particle motion model. The research results show that three main flow patterns are obtained, which are spiraling churn flow, spiraling annular flow, and spiraling annular twine flow. The ratio of the liquid-phase to gas-phase velocity VL/VG is the main factor that affects the existence of the gas phase. When VL/VG > 1/2, the flow pattern is a spiral cluster flow; when 1/5 < VL/VG< 1/2, the flow pattern is a spiral annular flow; and when VL/VG < 1/5, the flow pattern is a spiral annular flow. Compared with the flow pattern of the local spiral flow pattern of the short twisted band, it was found that the occurrence conditions of annular flow were postponed and a new flow pattern appeared. The research results of this paper have guiding significance for the pipeline risk management of natural gas hydrates and the engineering application of the full rotation of guide strips.