Flow Patterns Research Articles

Analysis and identification of gas-liquid two-phase flow pattern based on multivariate multi-scale dispersion entropy and interconnected dispersion pattern complex network

Gas-liquid two-phase flow is polymorphic and unstable. The investigation of the flow behavior of two-phase flow is vital for the application of gas-liquid transport in ocean engineering areas. We propose an analytical framework that combines multivariate multi-scale dispersion entropy (mvMDE) and interconnected dispersion pattern complex networks (IDPCN) for flow patterns. The resistance sensor array is used to capture the two-phase flow fluctuation signals in the riser, and the dimensionally reduced time series are nonlinearly mapped into a multivariate symbolic sequence. The mvMDE of the multivariate symbolic sequence is computed to measure the complexity of the flow pattern signals at the level of amplitude variation. In addition, a new multis-cale complex network based on the symbolic sequence is proposed to study the pseudo spatial coupling behavior of flow patterns. The evolution of the flow pattern from bubble to churn flow is quantitatively characterized using the mean value of the complex network indices in the optimal scale range. Finally, we construct the joint plane of mvMDE and two network indices to complete flow pattern identification. The research results show that the framework can effectively fuse multi-channel flow pattern information at different time scales to reveal the evolution mechanism of gas-liquid two-phase flow.

Experimental investigation of flow and sediment transport on an equilibrium beach formed by surging breaker

Flow patterns and sediment transport induced by breaking waves on a beach profile have been studied in a laboratory wave flume. Two parallel experiments were conducted on the same profiled rigid bed and sediment (mobile) bed, each subjected to identical wave forcing. The rigid bed experiments include measurements of bed shear stress and water-surface elevation, while the sediment bed experiments involve the measurement of pore-water pressures. The beach profile features a beach step leading to the generation of a hydraulic jump at the end of the rundown phase and accordingly forms a backwash vortex. The bed shear stress measurements revealed that the maximum onshore directed mean bed shear stress occurs after the wave breaking whereas the offshore directed one occurs during rundown at the same section. The increase of the bed shear stress with respect to that in the approaching wave boundary layer during the wave breaking and hydraulic jump processes can be by as much as a factor of 13 and 4, respectively. The effect of the wave breaking on turbulence is also more pronounced by a factor of 2.2 than the hydraulic jump in terms of r.m.s values of the fluctuating component of the bed shear stress. The pore pressure measurements showed that the vortex generated during the wave breaking creates an impulsive, upward-directed pressure gradient force that can be up to 1.2 times the submerged weight of the sediment. The sediment transport occurs in the sheet flow regime in a large part of the beach profile. The turbulence generated by the backwash vortex and the hydraulic jump at the beach step directly impacts the local sediment suspension which serves as the source for the advected sediment in the swash zone. The results are compared with a previous study that used the same methodology but involved plunging waves and the initial bed profile.

Ammonia two-phase flow patterns and condensation in the inclined smooth tubes

The paper reports the experimental study of the two-phase ammonia flow patterns and condensation in the upward and downward inclined tubes. The two-phase patterns have been studied by the photography method in the transparent quartz tube of ID 7.5 mm at the inclination of −90 to 90°, saturation temperature of 35–65 °C, mass velocity of 40–160 kg m−2 s−1 and vapour quality of 0.1–0.8. The Hewitt and Roberts (1969) [19] upward pattern map in interfacial momentum flux coordinates compiled for the high-pressure steam water flows was compared with the obtained ammonia patterns, showing satisfactory qualitative correspondence. However, the transition lines quantitatively are not accurate for ammonia, especially in churn-to-slug cases. Matching the two-phase patterns and ammonia condensation HTC identified in the prior study for the smooth tubes of ID 8 and 11 mm, a so-called forced convective condensation (flow velocity dependent) domination line has been clearly shown for the upward and downward flows. This line splits the boundary conditions, providing similar condensation HTC for the horizontal and upward/downward flows independently on the expected pattern and with the essentially reduced HTC at the upward/downward configuration. The existence of the HTC maximum for the ammonia flow at the inclination of −30° was proved and quantified experimentally for the broad range of boundary conditions in the ID 8 and 11 mm tubes. Matching the identified condensation HTC and the observed flow patterns allows us to conclude that the condensation HTC maximum is mainly determined by the change of stratified-wavy pattern on a smooth stratified one.

Analysis of the cross-flow features around two side-by-side rectangular cylinders

This study employs the lattice Boltzmann method (LBM) to numerically analyze the fluid flow around two side-by-side rectangular cylinders with an aspect ratio (AR) of 3:2. The gap spacing (G) between the cylinders is taken in the range 0–10 and the Reynolds number (Re) is fixed at 200. The numerical outcomes depict a strong correlation between flow patterns, force variations, gap spacing, and aspect ratio. Among these parameters, the latter ones strongly influence the flow-induced drag, lift, and pressure. The mean drag coefficient (CDmean), Strouhal number (St), and root-mean-square values of force coefficients exhibit rapid variations under the impact of these parameters for both cylinders. The observed outcomes further indicate that flow structures in the wake vary with changes in gap spacing. Five separate patterns of wake flow are detected, depending on varying gap spacing. These patterns include isolated bluff-body flow, flip-flopping flow, non-synchronized flow, modulated synchronized flow, and synchronized flow.

Distinct phylogeographic and population genetic patterns of decapod species across Mediterranean biogeographic barriers

Abstract The Mediterranean Sea is a semi-enclosed oceanic basin that communicates with the Atlantic Ocean and can be subdivided into seven geographical regions. It is considered a hotspot of biodiversity and is characterised by high rates of endemism. Over the past decades, many studies showed the presence of potential geographical breaks both across the Atlanto-Mediterranean transition and within the Mediterranean Sea. These investigations led to the identification of three distinct types of population genetic structures: (1) populations characterized by panmixia; (2) Atlanto-Mediterranean geographical partitioning; and (3) possible further subdivision between East and West Mediterranean basins. In this review, mainly focused on Christoph Schubart’s works and interests, we summarize the different patterns of gene flows across the Atlanto-Mediterranean transition and within the Mediterranean Sea, recorded for decapod species living in littoral zones. Although some species share similar biological traits, larval dispersal mechanisms and habitat preferences, differences in their phylogeographic and population genetic structures do emerge. These findings confirm the complex nature of gene flows across the Atlanto-Mediterranean transition and within the Mediterranean basin and how difficult it is to achieve a generalised picture of the phylogeographical patterns of Atlantic-Mediterranean species.

Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components

After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first long-pulse operation campaign. A maximum discharge length of 8 min was achieved with a total heating energy of 1.3 GJ. Safe divertor operation was demonstrated in attached and detached mode. Stable detachment is readily achieved in some magnetic configurations but requires impurity seeding in configurations with small magnetic pitch angle within the edge islands. Progress was made in the characterization of transport mechanisms across edge magnetic islands: Measurement of the potential distribution and flow pattern reveals that the islands are associated with a strong poloidal drift, which leads to rapid convection of energy and particles from the last closed flux surface into the scrape-off layer. Using the upgraded plasma heating systems, advanced heating scenarios were developed, which provide improved energy confinement comparable to the scenario, in which the record triple product for stellarators was achieved in the previous operation campaign. However, a magnetic configuration-dependent critical heating power limit of the electron cyclotron resonance heating was observed. Exceeding the respective power limit leads to a degradation of the confinement.

Experimental investigation on the aerodynamics and flow patterns of a 5:1 rectangular cylinder with spoilers

The current study experimentally investigates a passive control method for the flow field by placing spoilers symmetrically on the leading edge of a 5:1 rectangular cylinder. The Reynolds number (Re) is based on the inflow velocity and the height of the model. The length of the spoiler is equal to the span length of the model, and the width and angle are defined as w and α. At Re = 1.07 2.50×104, the surface pressure distribution of the model is obtained to initially investigate the effects of α and w on the aerodynamic characteristics. Based on the aerodynamic results, some cases are selected to reveal the control mechanism using the particle image velocimetry (PIV) technique. The proper orthogonal decomposition (POD) is adopted to analyze the POD modes and instantaneous flow. The results show that the spoiler with a certain α can suppress the aerodynamic forces of the model. Spoilers with a relative angle of 247.5° significantly reduce CL′ by 75 % and slightly reduce CD¯ by 5.5 %. Also, its TKE and RSS values are reduced by 56 % and 57 %, respectively. The PIV visualization shows that the spoiler affects the flow separation at the leading edge. Then, the rolling and interactions of shear layers are suppressed, making them tend to be parallel. Besides, spoilers with a relative angle of 67.5° almost eliminate the flow separation.

CO2 storage in saline aquifers: A simulation on quantifying the impact of permeability heterogeneity

As one promising technology to mitigate CO2 emission, CO2 capture utilization and storage (CCUS) plays a crucial role in achieving carbon neutrality. The deep saline aquifer is a prime candidate for CO2 geological storage. The subsurface flow and effectiveness of CO2 storage in deep saline aquifer are highly related to the permeability heterogeneity of formations, which needs in-depth study. To bridge the gap, this study focused on quantifying the impact of permeability heterogeneity on the CO2 flow patterns, the well injectivity and the storage efficiency, which aims to enhance the understanding of CO2 storage characteristics in deep saline aquifers. The heterogeneous saline aquifer model was built by using the Sequential Gaussian Simulation (SGSIM) method. A novel classification template was proposed with the CO2 flow patterns classified as “Dispersive”, “Sweeping”, “Fingering”, and “Channeling” for CO2 storage in deep saline aquifers according to the geostatistical parameters (including dimensionless correlation lengths, first and second spatial moment, and Dykstra-Parsons coefficient). For the well injectivity, the results showed that high injectivity occurred when both horizontal and vertical correlation lengths were high or at a favourable connectivity of permeability in the horizontal and vertical directions. In addition, CO2 storage efficiency is higher when both dimensionless horizontal and vertical correlation lengths are in the range of 0.1–0.2. This is because frequent changes between high and low permeability regions led to frequent mutual displacement of water and CO2, resulting in higher residual trapping and slow CO2 front. Therefore, the dimensionless correlation lengths and breakthrough time should be considered simultaneously to achieve safer trapping and maximize the CO2 storage capacity. The findings of this work provide insights into the subsurface flow of CO2 storage in deep saline aquifers with permeability heterogeneity.

Genetic diversity and population structure of the semiterrestrial crab Armases benedicti (Brachyura, Sesarmidae) along the North Brazilian coast

Abstract For coastal marine species, gene flow patterns are intricately shaped by environmental factors such as oceanographic currents and river plumes. Despite these natural barriers, pelagic larval duration and salinity tolerance potentially facilitate the movement of individuals, resulting in panmixia. This study utilized Cox1 mtDNA data to conduct population genetics and structure analysis of the semiterrestrial crab Armases benedicti along the North Brazilian coast. The haplotype network displayed a star-like configuration, indicating recent mutation events and confirming minimal genetic structure. While DAPC analysis identified three distinct genetic clusters, limited genetic differentiation and negligible structuring were evident between Amapá, the northmost coastal Brazilian state, and Pará (approx. 400 km from the Amapá sampling site). Maranhão (approx. 600 km from Pará) exhibited higher Fst values in all pairwise comparisons but remained just one mutational step away from other sites. Despite coastal barriers affecting genetic connectivity, our findings suggest that A. benedicti populations demonstrate low genetic differentiation, hinting at the minimal impact of the Amazon plume as a barrier to gene flow, possibly due to the species’ adaptability to brackish environments. However, employing more informative genetic markers and conducting complementary ecological studies on larval salinity tolerance remain crucial for a deeper understanding of Armases population dynamics and adaptive strategies.

Unveiling intricate foam behaviors and dynamic instabilities in a two-phase natural circulation loop with seawater

The use of seawater as an alternative emergency coolant in a nuclear power plant presents great potential to enhance the nuclear safety. The present study investigates the dynamic instabilities during the startup experiments of a natural circulation loop with seawater through synchronization of two-phase flow visualization and measurements of transient fluid flow parameters. The results reveal that in seawater the pressure drop oscillations (PDO) with nature of low-frequency pulse-type loop flow occurs at the modified heat flux of 531.56–654.80 kW/m2. On the other hand, the density wave oscillations (DWO) characterized by high-frequency oscillatory flow prevails at higher modified heat flux of 654.80–1844.46 kW/m2. For the loop with seawater, the flow patterns in the riser may evolve from dispersed bubbly flow, foam flow, foam and short slug flow due to the flashing effects, and foam and long slug flow periodically. The image analysis reveals that the foam fraction may decline from 75% to 52.2%, while the flow pattern transforms from the stage II (foam and cape bubbly flow) to III (foam and long slug flow). On the other hand, the flow pattern may evolve from bubbly flow, cap bubbly flow, turbulent slug flow, and long slug flow in de-ionized water. For DWO, the oscillatory frequency is found to be inlet temperature dependent. Interestingly, both fluids demonstrate identical frequencies of 0.06 Hz, 0.14 Hz, and 0.09 Hz, respectively, corresponding to the inlet temperature range of 40–52 °C, 52–65 °C, and 65–75 °C, despite significantly different evolution of two-phase flow patterns. Indeed, the density wave travels at the same speed through the loop operating at the same power for both seawater and de-ionized water, as the buoyancy force is the primary driving force for the present study. These findings contribute significantly to the better understanding of related industrial processes using seawater as the working fluid.

Study of a nano-coated hydrophilic polymer for indirect evaporative cooler from wetting, thermal and corrosion resistance performance

Hydrophilicity and evaporation rate of the wet channels play crucial effects on the cooling performance of an indirect evaporative cooler (IEC). Thus, great efforts are made to develop high-performance wet surface materials for IECs. However, current studies of hydrophilic coatings focus on the moisture diffusion ability of the material itself or the overall thermal performance of an IEC, with less in-depth research on the internal local thermal and quantitative wetting performance under various operating conditions. In this study, a TiO2/SiO2 nano-coating is applied to polypropylene (PP) by three treatment methods to develop a hydrophilic durable and corrosion-resistant PP for IEC application. Firstly, the hydrophilic durability of various samples was tested for 30 days. Secondly, test rigs were built for wetting and thermal performance investigation. The wetting performance was studied by both the drop-impact interaction test and the falling film experiment. The flow pattern, water film thickness, and wettability ratio were investigated under varying water flow rates, air velocity, and water distribution strategies (continuous spray, intermittent spray). The thermal performance including the internal wall temperature and supply air temperature of non-coated and coated IEC were comparatively tested. Finally, the corrosion resistance ability of samples was tested by acid salt spray. The results show that primer-aided TiO2/SiO2 coating on PP can provide durable hydrophilicity and corrosion resistance. Gaining better water retention ability, the thermal performance of nano-coated IEC can be enhanced under intermittent spray with 1.1 °C lower plate temperature and wet-bulb efficiency improved from 74.4 % to 81.4 % compared to the non-coated one.

Effects of SGLT2 inhibitors on parameters of renal venous congestion in intrarenal Doppler ultrasonography.

Cardiorenal syndrome is a common condition in clinical practice in which renal venous congestion (VC) plays an important role. Intrarenal Doppler ultrasound (IRD) is a non-invasive method to assess and quantify renal VC. The current study aims to investigate the effects of SGLT2 inhibitor (SGLT2i) therapy on IRD parameters of renal VC. This prospective observational study included patients with chronic kidney disease (CKD) with or without type 2 diabetes mellitus and/or heart failure (HF) with reduced and preserved ejection fraction who had an indication for standard of care SGLT2i therapy. IRD, assessing venous impedance index (VII), and intrarenal venous flow pattern (IRVF) analysis were performed within the interlobar vessels of the right kidney before and 6 months after initiation of SGLT2i therapy. A number of 64 patients with CKD and a cardiorenal risk profile were included (mean eGFR 42.9ml/min/1.73m2; 56% with HF, and 38% with type 2 diabetes mellitus). 17 patients exhibited signs of VC in the IRD. VII was significantly correlated with levels of NT-proBNP, female gender, NYHA class, and was significantly negative correlated with body mass index. After 6 months, a notable decrease in the mean VII of the right interlobar veins by 0.13 (P<.01) was observed. Stratification according to IRVF pattern showed a significant shift towards reduced renal VC pattern after 6 months (P=.03). In this study, SGLT2i therapy resulted in a reduction in renal VC as assessed by IRD. These findings underscore the potential haemodynamic benefits of SGLT2 inhibitors in cardiorenal syndrome and warrant further investigation into their clinical implications.

Teleseismic measurements of Upper Mantle Shear-Wave Anisotropy in Southern Mexico

The Mexican subduction system is an ideal region to study 3-D mantle deformation patterns in response to changes in slab geometry and the presence of tears. Shear-wave splitting measurements were made using SKS, SKKS, and PKS waves in southern Mexico, where the Cocos slab subducts beneath the North American and western Caribbean plates. For most of southern Mexico, the results are consistent with predominantly trench-normal fast polarization directions that can be interpreted as a consequence of sub-slab entrained flow and 2-D corner flow in the mantle wedge in the presence of A-type olivine fabric (or similar). This pattern of trench-perpendicular fast axes extends northward to the region southeast of the Trans-Mexican Volcanic Belt. Beneath its eastern end, fast axes rotate ∼20° clockwise and are likely controlled by the absolute motion of the North American plate. In southeastern Mexico, along the coast and above the mantle wedge tip, the fast axes are trench-normal and the delay times are the shortest. They were interpreted to result from a possibly serpentinized mantle wedge tip. In the same region above the mantle wedge core, the splitting parameters appear to result from different flow patterns in the mantle wedge and the sub-slab mantle.

Associations of Cerebral Blood Flow Patterns With Gray and White Matter Structure in Patients With Temporal Lobe Epilepsy.

Neuroimaging studies in patients with temporal lobe epilepsy (TLE) show widespread brain network alterations beyond the mesiotemporal lobe. Despite the critical role of the cerebrovascular system in maintaining whole-brain structure and function, changes in cerebral blood flow (CBF) remain incompletely understood in the disease. Here, we studied whole-brain perfusion and vascular network alterations in TLE and assessed its associations with gray and white matter compromises and various clinical variables. We included individuals with and without pharmaco-resistant TLE who underwent multimodal 3T MRI, including arterial spin labelling, structural, and diffusion-weighted imaging. Using surface-based MRI mapping, we generated individualized cortico-subcortical profiles of perfusion, morphology, and microstructure. Linear models compared regional CBF in patients with controls and related alterations to morphological and microstructural metrics. We further probed interregional vascular networks in TLE, using graph theoretical CBF covariance analysis. The effects of disease duration were explored to better understand the progressive changes in perfusion. We assessed the utility of perfusion in separating patients with TLE from controls using supervised machine learning. Compared with control participants (n = 38; mean ± SD age 34.8 ± 9.3 years; 20 females), patients with TLE (n = 24; mean ± SD age 35.8 ± 10.6 years; 12 females) showed widespread CBF reductions predominantly in fronto-temporal regions (Cohen d -0.69, 95% CI -1.21 to -0.16), consistent in a subgroup of patients who remained seizure-free after surgical resection of the seizure focus. Parallel structural profiling and network-based models showed that cerebral hypoperfusion may be partially constrained by gray and white matter changes (8.11% reduction in Cohen d) and topologically segregated from whole-brain perfusion networks (area under the curve -0.17, p < 0.05). Negative effects of progressive disease duration further targeted regional CBF profiles in patients (r = -0.54, 95% CI -0.77 to -0.16). Perfusion-derived classifiers discriminated patients from controls with high accuracy (71% [70%-82%]). Findings were robust when controlling for several methodological confounds. Our multimodal findings provide insights into vascular contributions to TLE pathophysiology affecting and extending beyond mesiotemporal structures and highlight their clinical potential in epilepsy diagnosis. As our work was cross-sectional and based on a single site, it motivates future longitudinal studies to confirm progressive effects, ideally in a multicentric setting.

The influence of collar parameters on local scour mechanism around the circular pier at the bend

Analysis of bridge failures due to scouring has been extensively studied by different researchers in recent years and as a result various methods of controlling local scour cavity have been given. Since most of the research in this field has been done on straight paths and also the complexity of the flow pattern in bends, studying the scouring pattern around the bridge piers located in the bends has become a necessity. Therefore, one of the main objectives of this study is to investigate the scouring around the circular piers which are protected by collars at the river bends. The performance of the collar significantly depends on its level around the pier, which has been studied in this study. The results showed that the optimal performance of this structure, in positions 60°, 90° and 120° at the level of 0.2 pier width under the bed with 3 mm thickness (0.06 of pier width) by approximately 68, 63 and 70% of the maximum pier scour depth was reduced compared with collarless pier, respectively. By analyzing the results of this research, it was observed that the optimum level range of collar around the pier at various bend angles is the initial bed level up to 0.4 times the pier width at the bottom of the incipient level of the bed. Moreover, getting closer to the plate placement level toward the initial bed elevation enhances the collar’s function in decreasing scouring.

Numerical simulation of arc stabilizing cycle in vacuum arc remelting of titanium alloy

Through utilizing numerical simulation methods, the flow state of the molten pool during the vacuum self-consumption melting process of titanium alloy was analyzed. The influence of the stable arc cycle on the shape of the molten pool, dendrite arm spacing, surface quality, and shrinkage cavity was examined. The results showed that without an external magnetic field, the molten pool for smelting a Φ720 mm specification titanium alloy ingot is dominated by self-inductance magnetic force, leading to a downward flow in the central part of the melt. A mere 0.5 G stray magnetic field can result in Ekman pumping, causing an upward secondary flow in the core to counteract it. At an externally added magnetic field strength of 50 G, choosing a 10 s-20 s cycle can achieve a relatively stable double loop flow pattern. The shape of its molten pool, dendrite arm spacing, and contact ratio all reach optimal performance, thus verifying the possibility and feasibility of the double loop flow, and the macroscopic segregation of the simulated ingots essentially matches the experimental results, aiming to provide references for selecting parameters in actual production.

Study of oblique granular impingement flow through CFD-DEM simulations and energy consumption statistics

This paper investigates an experimental granular impingement flow system through simulations and energy consumption statistics. With the increase of solid concentration, flow patterns undergo cross flow (dense edge and dilute center), dispersed flow, and mixed-jet flow (dilute edge and dense center) in turn. The influence of gas phase on the flow pattern was investigated. According to the analysis of force and time-averaged velocity, it is revealed that gas-solid interaction will cause energy dissipation of granular flow, which cannot be ignored in specific cases. Then, a flow map is proposed according to both the Archimedes number and solid concentration. In addition, the flow pattern transition and local structure variations can be reflected by energy consumption statistics. Based on the simulations and methods developed in this work, it is promising to deepen the understanding and study of granular impingement flow from the viewpoints of energy consumption and new-type flow map.

Investigating hydrodynamics and turbulent effects in rivers for different flow conditions using spatial complexity metrics

In non-uniform river flows, hydrodynamic features, such as gradients of velocity in flow directions, are of particular importance for explaining the abundance of aquatic habitats. Hydraulic complexity metrics referred to as M1, M2, and M3 play an important role when it comes to the analysis of habitat metrics on a 3D spatial level. Parameter M1 is proportional to the drag force experienced by an organism, parameter M2 represents how much more energy an organism must expend if it moves from the lower velocity to the higher velocity location, and parameters M3 illustrates the circulation in flow. The specific aim of the present study is to apply those parameters to characterize, under different flow conditions, the cross-sectional distribution of kinetic energy and coherent structures which are both relevant for many aquatic organisms. To this aim, laboratory data as well as field observations along Tiber River, in central Italy, were considered and the hydraulic complexity metrics were investigated in dimensionless form. On the laboratory-scale, the dimensionless parameters M1*, M2* and M3* identify the velocity gradient related to the high/low cross-sectional velocity and the high/low vorticity areas in selected cross-sections along the flume. Then, the evaluation of the parameter M2* in the horizontal plane allows to verify the relation between the localization of the high/low kinetic energy areas in the longitudinal direction. For the field-scale, the parameters were investigated, under high, moderate and low flow conditions, in a gauged site in the Tiber River. The results indicate that an aquatic organism should spend more energy where M3*, which is related to flow circulation, assumes high values. Furthermore, significant values of M1* and M2* are observed, which are linked to gradients in the cross-sectional distribution of velocity. These values are predominantly found at the river centerline for M1* and at the banks for M2*. In terms of echo-hydraulics, the results based on both laboratory and field data indicate that they are complementary, showing that for the larger magnitudes of M1 and M3, which are related to the kinetic energy and flow circulation, respectively, an aquatic organism should spend more energy in these zones. Overall, the results based on both laboratory and field studies suggest that parameters M1 and M2 are inversely linked, i.e., M1 decreased with increasing M2, while, there is no relationship between parameters M3 and M1. The findings of the present research would be of particular interest in quantifying biologically important flow patterns occurring at different spatial scales within different streams and under different flow conditions.

Physics-data fusion for digital metering of gas-liquid two-phase flow in oil nozzles

Oil well production metering is an important basis for assessing resource reserves and production capacity. Existing metering methods require high investment and involve significant implementation difficulties and high computational costs. A new method of multiphase flow metering method was proposed by combining the fluctuation of pressure drop and temperature difference generated after throttling through the oil nozzle. The throttling equation coupling differential pressure, flow rate and gas fraction was derived. By regulating the gas and liquid superficial velocity, we carried out the experimental test for true nozzle aperture of 10 mm in the loop system, covering various flow patterns. In addition, the deep neural network was constructed for inversion prediction of mass gas fraction. The proposed flow metering equation has an adaptable gas mass fraction range of 0 to 100%, unaffected by the variations in flow patterns, gas-liquid velocities, and system pressure changes. The metering errors of gas mass fraction and mass flow rate is below ±10%. The proposed metering method only relies on the existing temperature and pressure measurement system in the gathering and transportation system, and no additional measuring devices are required. It can be widely used in oil filed production to realize the virtual metering.

An eigenvalue problem for self-similar patterns in Hele-Shaw flows

Hele-Shaw problems are prototypes to study the interface dynamics. Linear theory suggests the existence of self-similar patterns in a Hele-Shaw flow. That is, with a specific injection flux the interface shape remains unchanged while its size increases. In this paper, we explore the existence of self-similar patterns in the nonlinear regime and develop a nonlinear theory characterizing their fundamental features. Using a boundary integral formulation, we pose the question of self-similarity as a generalized nonlinear eigenvalue problem, involving two nonlinear integral operators. The nonlinear flux constant Cf is the eigenvalue and the corresponding self-similar pattern x̃ is the eigenvector. We develop a quasi-Newton method to solve the problem and show the existence of nonlinear shapes with k-fold dominated symmetries. Nonlinear results are compared with the established linear theory, demonstrating a divergence between the two due to non-linear effects absent in the linear stability analysis. Further, we investigate how sensitive the shape of the interface is to the viscosity. Additionally, we conduct numerous numerical experiments using a wide range of initial guesses and initial flux constants. Through these experiments, one is able to obtain a diagram of self-similar shapes and the corresponding flux. It could be used to verify possible self-similar shapes with a proper initial guess and initial flux constant. Our results go beyond the predictions of linear theory and establish a bridge between the linear theory and simulations.