Types Of Flow Regimes Research Articles

Tomographic multiphase flow measurement

Measurement of multiphase flow of gas, oil and water is not at all trivial and in spite of considerable achievements over the past two decades, important challenges remain (Corneliussen et al., 2005). These are related to reducing measurement uncertainties arising from variations in the flow regime, improving long term stability and developing new means for calibration, adjustment and verification of the multiphase flow meters. This work focuses on the first two issues using multi gamma beam (MGB) measurements for identification of the type of flow regime. Further gamma ray tomographic measurements are used for reference of the gas/liquid distribution. For the MGB method one Am-241 source with principal emission at 59.5keV is used because this relatively low energy enables efficient collimation and thereby shaping of the beams, as well as compact detectors. One detector is placed diametrically opposite the source whereas the second is positioned to the side so that this beam is close to the pipe wall. The principle is then straight forward to compare the measured intensities of these detectors and through that identify the flow pattern, i.e. the instantaneous cross-sectional gas-liquid distribution. The measurement setup also includes Compton scattering measurements, which can provide information about the changes in the water salinity for flow segments with high water liquid ratio and low gas fractions. By measuring the transmitted intensity in short time slots (<100ms), rapid regime variations are revealed. From this we can select the time sections suitable for salinity measurements. Since the salinity variations change at the time scale of hours, a running average can be performed to increase the accuracy of the measurements. Recent results of this work will be presented here.

Characterizing Curvilinear Features Using the Localized Normal‐Score Ensemble Kalman Filter

The localized normal‐score ensemble Kalman filter is shown to work for the characterization of non‐multi‐Gaussian distributed hydraulic conductivities by assimilating state observation data. The influence of type of flow regime, number of observation piezometers, and the prior model structure are evaluated in a synthetic aquifer. Steady‐state observation data are not sufficient to identify the conductivity channels. Transient‐state data are necessary for a good characterization of the hydraulic conductivity curvilinear patterns. Such characterization is very good with a dense network of observation data, and it deteriorates as the number of observation piezometers decreases. It is also remarkable that, even when the prior model structure is wrong, the localized normal‐score ensemble Kalman filter can produce acceptable results for a sufficiently dense observation network.

Characteristics of the Interfacial Wave Velocity on the Liquid Film of Annular Flow for Gas-Oil-Water Three-Phase Flow in a Horizontal Pipe

The experiments were conducted in a horizontal multiphase flow test loop (50mm inner diameter, 40m long) and the cross-correlation technology was used for the study of the characteristics of the interfacial wave velocity about two types of annular flow regimes (AN║DO/W and AN║DW/O) for gas-oil-water three-phase flow. The results show that the interfacial wave velocity on the liquid film of AN║DO/W flow pattern and AN║DW/O flow pattern all increases with the increase of gas superficial velocity and liquid superficial velocity on the condition of fixed ratio of oil and water flow rates, but the difference is that the increase is a linear monotonic increase for AN║DO/W flow pattern and a non-linear increase for AN║DW/O flow pattern, and the liquid superficial velocity makes a larger contribution than the gas superficial velocity. The interfacial wave velocity also increases with the increase of input water cut in liquid at different gas superficial velocities under the conditions of liquid superficial velocity fixed.

Turbulence- and buoyancy-driven secondary flow in a horizontal square duct heated from below

Direct numerical simulations of fully developed turbulent flows in a horizontal square duct heated from below are performed at bulk Reynolds numbers Reb = 3000 and 4400 (based on duct width H) and bulk Richardson numbers 0≤Ri≤1.03. The primary objective of the numerical simulations concerns the characterization of the mean secondary flow that develops in this class of flows. On one hand, it is known that turbulent isothermal flow in a square duct presents secondary mean motions of Prandtl’s second kind that finds its origin in the behavior of turbulence structures. On the other hand, thermal convection drives a mean secondary motion of Prandtl’s first kind directly induced by buoyancy. As far as the mean structure of the cross-stream motion is concerned, it is found that different types of secondary flow regimes take place when increasing the value of the Richardson number. The mean secondary flow in the range 0.025≲Ri≲0.25 is characterized by a single large-scale thermal convection roll and four turbulence-driven corner vortices of the opposite sense of rotation to the roll, as contrasted with the classical scenario of the eight-vortex secondary flow pattern typical of isothermal turbulent square-duct flow. This remarkable structural difference in the corner regions can be interpreted in terms of combined effects, on instantaneous streamwise vortices, of the large-scale circulation and of the geometrical constraint by the duct corner. When further increasing the Richardson number, i.e., Ri ≳ 0.25, the structure of the mean secondary flow is solely determined by the large-scale circulation induced by the buoyancy force. In this regime, the additional mean cross-stream motion is characterized by the presence of two distinct buoyancy-driven vortices of opposite sense of rotation to the circulation only in two of the four corner regions. With increasing Ri, the large-scale circulation is found to enhance the wall skin friction and heat transfer. In the significant-buoyancy regime Ri ≳ 0.25, the mean cross-stream motion and its rms fluctuations are found to scale, respectively, with the buoyancy-induced velocity ug=gβΔTH (g, β, and ΔT being the gravity acceleration, the volumetric coefficient of thermal expansion, and the temperature difference across the duct, respectively) and with the mixed velocity scale (ν/H)ug (ν being the kinematic viscosity). It is suggested that the probable scalings for the rms of streamwise velocity component and of temperature fluctuation are related with the friction velocity uτ and friction temperature Tτ according to the magnitudes uτ2/(ν/H)ug and Tτuτ/(ν/H)ug, respectively.

River regimes and recent hydrological changes in the Duero basin (Spain)

Summary River regimes are key tools in water management as they enable prediction of minimum and maximum flows throughout the year. In the Mediterranean region, flow regimes are very sensitive to climatic variations, and are likely to change with the declining precipitation and higher temperatures predicted for the future. This study explores variability in river regimes of the Duero basin (northern Spain), and changes therein over the period 1961–2006. Principal component analyses were used to classify the main types of flow regimes across the basin, and to identify the most common patterns in the monthly streamflow trends. Three types of river regime were identified: (1) a rainfall-based regime with a peak flow in winter, spatially corresponding to the middle and lower reaches of the rivers; (2) a snow–rainfall regime in the headwaters, with high flows in spring; and (3) a human-induced regime, with peak flows in summer because of release of water stored in spring. There was a marked reduction in river discharge in winter and spring over the course of the study period, leading to significant changes in both the magnitude and timing of flows. These results indicate that river regimes have changed in the direction of reduced flow volumes and shifts in peak flows. The causes appear to be decreasing winter precipitation and a reduction in the snowmelt component, presumably due because of increasing temperatures in winter and spring.

Integrated cave drip monitoring for epikarst recharge estimation in a dry Mediterranean area, Sif Cave, Israel

AbstractUnderstanding recharge mechanisms and controls in karst regions is extremely important for managing water resources because of the dynamic nature of the system. The objective of this study was to evaluate water percolation through epikarst by monitoring water flow into a cave and conducting artificial irrigation and tracer experiments, at Sif Cave in Wadi Sussi, Israel from 2005 through 2007.The research is based on continuous high‐resolution direct measurements of both rainfall and water percolation in the cave chamber collected by three large PVC sheets which integrate drips from three different areas (17, 46, and 52 m2). Barrels equipped with pressure transducers record drip rate and volume for each of the three areas. The combined measured rainfall and cave data enables estimation of recharge into the epikarst and to better understand the relationship of rainfall‐recharge. Three distinct types of flow regimes were identified: (1) ‘Quick flow’ through preferential flow paths (large fractures and conduits); (2) ‘Intermediate flow’ through a secondary crack system; and (3) ‘Slow flow’ through the matrix. A threshold of ∼100 mm of rain at the beginning of the rainy season is required to increase soil water content allowing later rainfall events to percolate deeper through the soil and to initiate dripping in the cave. During winter, as the soil water content rises, the lag time between a rain event and cave drip response decreases. Annual recharge (140–160 mm in different areas in the cave) measured represents 30–35% of annual rainfall (460 mm). Copyright © 2011 John Wiley &amp; Sons, Ltd.

Reply to comment by Keith Richardson on “Flow regimes, bed morphology, and flow resistance in self‐formed step‐pool channels”

Reply to comment by Keith Richardson on “Flow regimes, bed morphology, and flow resistance in self‐formed step‐pool channels”

Relationships of coastal nocturnal boundary layer winds and turbulence to Houston ozone concentrations during TexAQS 2006

Measurements made with a ship‐based Doppler wind lidar during the summertime 2006 Texas Air Quality Study are used to study the relationship between lower‐tropospheric vertical structure and winds and ozone (O3) concentrations in Houston, Texas, under two different flow regimes. We observed that strong southerly flow regimes, dominated by the subtropical anticyclone (Bermuda high) off the Atlantic coast of the United States, resulted in strong (i.e., high wind speed) onshore nocturnal low‐level jets (LLJ) and low O3 and oxidant Ox (where Ox = O3 + NO2) concentrations at night and the following afternoon. In contrast, periods dominated by northerly or easterly flow resulted in relatively weak (low wind speed), but still onshore, nocturnal LLJs associated with higher concurrent and next‐day concentrations of O3 and Ox. We present lidar data from 24 h example periods for each of these conditions and demonstrate how each type of flow regime is related to in situ ship‐based ozone measurements. We expanded the study to include all days during the study when the ship was near Houston, to demonstrate how the strength of the meridional winds aloft show a better relationship to concurrent ship‐measured Ox concentrations than the winds near the surface do. We found a strong relationship between a parameterization of the observed nocturnal jets, which reflect the synoptic conditions, to peak hourly O3 measured the next day at the ship and averaged throughout the Houston/Galveston/Brazoria continuous ambient monitoring stations monitoring network, indicating potential applications for planning air quality.

Numerical simulation of pollutant flow and dispersion in different street layouts

The objective was to simulate the pollutant emissions from vehicle exhausts in a street canyon and to investigate the impact of street canyon geometry including canyon height to width ratio (h/w) and relative height (h2/h1) to the flow structure and air pollutant dispersion. The paper reports work on 15 canyon cases, when the validation of the numerical model was evaluated using an extensive wind tunnel experiment (Kastner‐Klein and Plate). We found the modified RNG k‐ϵ turbulence model to be the optimum model. The pollutant transport and diffusion greatly depends on the street canyon configuration and the type of flow regimes inside the canyon. We calculated the retention values of 15 canyon cases reflecting the dispersion ability of air pollutants from the sources out to the free stream. The results obtained indicated that the air pollutant retention value is the minimum that is favourable in a street canyon configuration for pollutant dispersion.

The ecological limits of hydrologic alteration (ELOHA): a new framework for developing regional environmental flow standards

Summary1. The flow regime is a primary determinant of the structure and function of aquatic and riparian ecosystems for streams and rivers. Hydrologic alteration has impaired riverine ecosystems on a global scale, and the pace and intensity of human development greatly exceeds the ability of scientists to assess the effects on a river‐by‐river basis. Current scientific understanding of hydrologic controls on riverine ecosystems and experience gained from individual river studies support development of environmental flow standards at the regional scale.2. This paper presents a consensus view from a group of international scientists on a new framework for assessing environmental flow needs for many streams and rivers simultaneously to foster development and implementation of environmental flow standards at the regional scale. This framework, the ecological limits of hydrologic alteration (ELOHA), is a synthesis of a number of existing hydrologic techniques and environmental flow methods that are currently being used to various degrees and that can support comprehensive regional flow management. The flexible approach allows scientists, water‐resource managers and stakeholders to analyse and synthesise available scientific information into ecologically based and socially acceptable goals and standards for management of environmental flows.3. The ELOHA framework includes the synthesis of existing hydrologic and ecological databases from many rivers within a user‐defined region to develop scientifically defensible and empirically testable relationships between flow alteration and ecological responses. These relationships serve as the basis for the societally driven process of developing regional flow standards. This is to be achieved by first using hydrologic modelling to build a ‘hydrologic foundation’ of baseline and current hydrographs for stream and river segments throughout the region. Second, using a set of ecologically relevant flow variables, river segments within the region are classified into a few distinctive flow regime types that are expected to have different ecological characteristics. These river types can be further subclassified according to important geomorphic features that define hydraulic habitat features. Third, the deviation of current‐condition flows from baseline‐condition flow is determined. Fourth, flow alteration–ecological response relationships are developed for each river type, based on a combination of existing hydroecological literature, expert knowledge and field studies across gradients of hydrologic alteration.4. Scientific uncertainty will exist in the flow alteration–ecological response relationships, in part because of the confounding of hydrologic alteration with other important environmental determinants of river ecosystem condition (e.g. temperature). Application of the ELOHA framework should therefore occur in a consensus context where stakeholders and decision‐makers explicitly evaluate acceptable risk as a balance between the perceived value of the ecological goals, the economic costs involved and the scientific uncertainties in functional relationships between ecological responses and flow alteration.5. The ELOHA framework also should proceed in an adaptive management context, where collection of monitoring data or targeted field sampling data allows for testing of the proposed flow alteration–ecological response relationships. This empirical validation process allows for a fine‐tuning of environmental flow management targets. The ELOHA framework can be used both to guide basic research in hydroecology and to further implementation of more comprehensive environmental flow management of freshwater sustainability on a global scale.

Near-critical CO 2 liquid--vapor flow in a sub-microchannel. Part II: Flow regimes

The mean-field free-energy LBM is used to investigate the liquid--vapor flow regimes in a two-dimensional 200 nm channel with near-critical CO 2 at temperature 25 oC and pressure 6.434 MPa as the working fluid. Flow regimes over vapor qualities ranging from 0.01⩽ x⩽0.90, Weber numbers O(10 −2)⩽ We⩽ O(10 3), and capillary numbers O(10 −2)⩽ Ca⩽ O(10) are investigated. Three major types of flow regimes are encountered -- dispersed flow, bubble/plug flow, and liquid strip flow, each of which encompasses variations of the basic flow regime. The three major flow regimes with all their variations can be further classified into two major categories – regular and irregular. Irregular flow regimes are characterized by a distorted interface, including distorted bubble/slug flow, intermittent strip flow, wavy strip flow, and wispy-strip flow. Flows in which the interface is ordered and symmetric such as bubble/plug and strip flows are classified as regular flow regimes. It is found that the transition from regular to irregular flow regimes occurs at Weber number between 500 and 1000, independent of the vapor quality. Although no experiments exist at the same conditions, comparison of the predicted transition between regular and irregular regimes shows the same qualitative trends as experiments found in the literature.

Experimental Study of CO2 Injection Into Saline Formations

Summary We present laboratory experiments to investigate the influence of gravitational, viscous, and capillary effects on the CO2 injection process. Quasi 2D experiments are performed in a vertical glass-bead pack in the parameter range of interest for CO2 sequestration in deep aquifers (i.e., with Bond numbers of approximately 10−3 and capillary numbers on the order of 10−4). The objective is to investigate the type of flow regimes that occur under favorable as well as unfavorable conditions of density and viscosity. The experiments demonstrate the existence of pore-scale instability in the presence of unfavorable gradients of viscosity and density. Consequently, conventional mathematical models may not be able to represent these unstable flows appropriately. A comparison with estimates from percolation theory shows reasonably good agreement with experimental observations.

Two-phase flow regimes and mechanisms of critical heat flux under subcooled flow boiling conditions

A literature review of critical heat flux (CHF) experimental visualizations under subcooled flow boiling conditions was performed and systematically analyzed. Three major types of CHF flow regimes were identified (bubbly, vapor clot and slug flow regime) and a CHF flow regime map was developed, based on a dimensional analysis of the phenomena and available experimental information. It was found that for similar geometric characteristics and pressure, a Weber number ( We)/thermodynamic quality ( x) map can be used to predict the CHF flow regime. Based on the experimental observations and the review of the available CHF mechanistic models under subcooled flow boiling conditions, hypothetical CHF mechanisms were selected for each CHF flow regime, all based on a concept of wall dry spot overheating, rewetting prevention and subsequent dry spot spreading. Even though the selected concept has not received much attention (in term or theoretical developments and applications) as compared to other more popular DNB models, its basis have often been cited by experimental investigators and is considered by the authors as the “most-likely” mechanism based on the literature review and analysis performed in this work. The selected modeling concept has the potential to span the CHF conditions from highly subcooled bubbly flow to early stage of annular flow and has been numerically implemented and validated in bubbly flow and coupled with one- and three-dimensional (CFD) two-phase flow codes, in a companion paper. [Le Corre, J.M., Yao, S.C., Amon, C.H., in this issue. A mechanistic model of critical heat flux under subcooled flow boiling conditions for application to one and three-dimensional computer codes. Nucl. Eng. Des.].

Influence of hydrological regimes on the pre‐spawning entry of Atlantic salmon (Salmo salar L.) into an upland river

AbstractThe Girnock Burn is an Atlantic salmon (Salmo salar) spawning tributary of the river Dee, Aberdeenshire, Scotland. The dates, sexes and numbers of adult salmon entering the stream in the three months prior to spawning were determined between 1969 and 2005 using a permanent fish‐trap. During this time, the number of fish returning to spawn varied markedly. Here we analyze the whole of this unique long term data set in order to characterize and classify the hydrologic regimes of the pre‐spawning migration period and assess the extent to which these regimes help explain the timing and patterns of arrival of adult salmon into the stream. A range of flow parameters was calculated for the arrival period (September–November) for each of the 37 years. These parameters were used to ordinate and classify years according to their flow regimes. The analysis yielded six distinct groups or ‘flow regime types’ which separated principally in relation to flow magnitude and frequency parameters. The number of fish entering the burn on a given day was not significantly correlated to discharge on that day. However, patterns of arrival of fish differed markedly between years with different regime types, with the number of fish arriving on a given day related to patterns of discharge over the preceding part of the arrival period. Overall inter‐annual variability in entry corresponded to the defined regime types. In wetter years, fish entry to the stream usually starts relatively early and continues throughout the pre‐spawning period. In contrast, dry years may result in fish entry being delayed; this may result in lower numbers of spawning females entering the stream and sub‐optimal utilization of juvenile habitat in the following spring. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Core flow modelling assumptions

Modelling of core flows at the core-mantle boundary from secular variation (SV) requires a range of both physical and mathematical assumptions in order to derive a solution. We investigate the role of certain assumptions and an L 1 norm iterative inversion method to derive core flow models. Using three datasets of SV, we separate the effects of: (a) the assignment of observation errors through the data covariance matrix, (b) the a priori constraints placed upon the solution and (c) the type of flow regime assumed to be present in the core. Flow is calculated directly from the time derivatives of the X, Y and Z components of ground-based observatories rather than Gauss coefficients of the SV. We find the L 1 iterative method improves the fit of the SV generated by the flow models to the observed data, compared to the L 2 norm (least-squares) method. Using this method, we find a new class of flow solutions explaining the SV: purely poloidal flows, which fit the input data adequately and, for one of our datasets, better than toroidal-only flows. The patterns of motions is very different from that seen in previous flow models, which are dominated by their toroidal component.

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

A comparative analysis of cladoceran communities from different water body types: patterns in community composition and diversity

To develop strategies for the management and protection of aquatic biodiversity in water bodies at the landscape scale, there is a need for information on the spatial organization of diversity in different types of aquatic habitats. In this study, we compared the cladoceran composition and diversity between wheel tracks, pools, ponds, lakes, ditches, and streams, in 18 different areas of Flanders (Belgium). Multivariate analysis revealed significant differences in the composition of cladoceran communities among the different water body types. Average local and total diversity tended to be highest for lakes and lowest for streams. Despite the relatively high number of species supported by lakes, small water bodies seem to contribute considerably more to the total cladoceran richness of an average landscape in Flanders than lakes, because of their high abundance. With respect to biodiversity conservation at the landscape scale, our results point to the importance of maintaining a diversity of water body types of different size, permanence and flow regimes.

Coolant channel module CCM: An universally applicable thermal-hydraulic drift-flux based mixture-fluid 1D model and code

A complete and detailed description of the theoretical background of an ‘(1D) thermal-hydraulic drift-flux based mixture-fluid’ coolant channel model and its resulting module CCM will be presented. The objective of this module is to simulate as universally as possible the steady state and transient behaviour of the key characteristic parameters of a single- or two-phase fluid flowing within any type of heated or non-heated coolant channel. Due to the possibility that different flow regimes can appear along any channel, such a ‘basic (BC)’ 1D channel is assumed to be subdivided into a number of corresponding sub-channels (SC-s). Each SC can belong to only two types of flow regime, an SC with just a single-phase fluid, containing exclusively either sub-cooled water or superheated steam, or an SC with a two-phase mixture flow. After an appropriate nodalisation of such a BC (and therefore also its SC-s) a ’modified finite volume method’ has been applied for the spatial discretisation of the partial differential equations (PDE-s) which represent the basic conservation equations of thermal-hydraulics. Special attention had to be given to the possibility of variable SC entrance or outlet positions (which describe boiling boundaries or mixture levels) and thus the fact that an SC can even disappear or be created anew. The procedure yields for each SC type (and thus the entire BC), a set of non-linear ordinary 1st order differential equations (ODE-s). To link the resulting mean nodal with the nodal boundary function values, both of which are present in the discretised differential equations, a special quadratic polygon approximation procedure (PAX) had to be constructed. Together with the very thoroughly tested packages for drift-flux, heat transfer and single- and two-phase friction factors this procedure represents the central part of the here presented ‘Separate-Region’ approach, a theoretical model which provides the basis to the very effective working code package CCM. This package can be adopted as a general element in the simulation of thermal-hydraulic situations of complex systems consisting of a number of special channels. Such systems can represent different types of steam generators, 3D nuclear reactor cores with special attention to the calculation of the mass flow distribution into different parallel channels after non-symmetric perturbations, each of them distinguished by their key numbers. The resulting set of equations can be combined with other ODE-s and constitutive equations from additional parts of such a comprehensive model. The complete system of equations can then (outside of the CCM) be solved by applying appropriate integration routines. Verification and validation test runs over a wide application range have yielded very satisfactory results demonstrating therefore in a convincing way the quality of the CCM. This approach offers an alternative to the currently dominant ‘Separate-Phase Models’ where each phase within a coolant channel is treated separately. The advantages and disadvantages of these two approaches are discussed in this paper.

Numerical investigation on gas-displacement of a shear-thinning liquid and a visco-plastic material in capillary tubes

An elliptic mesh generation technique, with the Galerkin Finite Element Method is used to compute the free surface of the two-phase flow problem of a gas displacing a non-Newtonian material in a capillary tube. Two classes of non-Newtonian materials were investigated: a power-law shear-thinning liquid and a visco-plastic material with the viscosity function proposed by Papanastasiou [T.C. Papanastasiou, Flows of materials with yield-stress, J. Rheol. 31 (1987) 385–404]. The results were given as a function of a non-Newtonian capillary number and a rheological dimensionless parameter: the behavior index in the shear-thinning liquid case and a dimensionless yield-stress (equivalent to Bingham number) in the visco-plastic material. The goal of the present work is to study flow patterns, configuration of the interface between the two phases, and fraction of the mass of non-Newtonian material deposited at the wall, as functions of the dimensionless numbers cited. Some general results of experimental and numerical works found in literature were reproduced with a quite good agreement and a wider range of the dimensionless numbers was investigated. In both classes of materials studied, as the displaced fluid departs from Newtonian behavior, the fraction of the mass deposited on the tube wall decreases and the shape of the interface becomes flatter. It was offered a plausible explanation for this counter-intuitive result related to visco-plastic fluid, i.e. an apparent increase of its viscosity (increasing the dimensionless yield-stress number), induces a decrease of the layer thickness left behind. Concerning flow patterns, it was possible to identify ranges, dependent on rheological properties and capillary number, where the transition between bypass flows and fully recirculating flows occurs. In the Newtonian case all the flow patterns predicted by Taylor [G.I. Taylor, Deposition of a viscous fluid on the wall a tube, J. Fluid Mech. 10 (1961) 161–165] were well captured. In the visco-plastic and pseudo-plastic case it was found an interesting type of intermediate flow regime which is not present in the Newtonian transition.

ICONE15-10338 FLOW REGIME IDENTIFICATION AND ANALYSIS IN ADIABATIC UPWARD TWO-PHASE FLOW IN AN ANNULUS GEOMETRY

The main objective of this work is to identify and analyze two-phase flow regimes in adiabatic upward flow conditions in an concentric annulus geometry with an inner diameter of 19.1 mm and an outer diameter of 38.1 mm, at three axial locations (z/D_H: 51.5, 148.8, 229.9). In this regard, both Global Flow Regimes (GFRs) and Local Flow Regimes (LFRs) have been identified. In both cases, neural networks techniques have been used to obtain objective identification results. However, the flow regime indicator will be different depending on the type of flow regime: the cumulative probability distribution function (CPDF) of the area averaged void fraction obtained by impedance meters in the case of GFRs and the CPDF of the bubble chord length measured by a four-sensor conductivity probe in the case of LFRs. The GFRs maps have been compared with those obtained in previous research works and flow regime transitions existing correlations. The LFRs have been identified in five radial locations. The LFRs combinations maps have been compared with the GFRs and those combinations obtained in round pipes.