Four-sensor Probe Research Articles

Gas-liquid bubbly flow structure in a vertical large-diameter square duct

An experimental study was performed on the local structure of atmospheric upward-moving air–water two-phase flow in a vertical large-diameter square duct with a cross-section of 100 mm × 100 mm and a height of 3 m by using a four-sensor probe at the axial position of z/DH = 29.2. The flow regime was simultaneously observed by a high speed camera at z/DH = 12.5. The four-sensor probe method classifying spherical and non-spherical bubbles was applied as a key measurement way to obtain local parameters such as 3-D bubble velocity vector, bubble diameter and interfacial area concentration, which are necessary for people to know the internal flow structures as well as local void fraction change. The local measurements were performed at 66 points within an octant symmetric triangular area of the cross-section, which agreed well with area-averaged void fractions from differential pressure gauges and the superficial gas velocity from air flow meters. Both the local void fraction and interfacial area concentration indicated radial core-peak and wall-peak distributions at low and high liquid flow rates respectively. Main flow component of the bubble velocity vector showed a power-law distribution shape with its center peak increasing with the liquid flow rate. The 2 components of the bubble velocity vector in the cross-section revealed that there exists a rotating secondary flow in the octant symmetric triangular area and the magnitude of the rotating secondary flow increases with the liquid flow rate. Some of constitutive correlations of drift-flux model for rectangular flow channels and large-diameter circular flow channels and interfacial area concentration correlations for small-diameter and large-diameter circular flow channels are selected and reviewed to study their predictabilities against the present experimental data. The comparison study shows that the drift-flux correlations by Hibiki and Ishii (2003) reasonably predict void fraction and the interfacial-area-concentration correlations by Hibiki and Ishii (2002) and Shen and Hibiki (2015) can be recommended for the prediction of interfacial area concentration in the bubbly flows in large-diameter square ducts.

Characterization of horizontal air–water two-phase flow in a round pipe part II: Measurement of local two-phase parameters in bubbly flow

The current work seeks to develop an additional database in air–water horizontal bubbly flow through a 3.81cm inner diameter test section with a total development length of approximately 250 diameters. The experimental conditions are chosen to cover a wide range of the bubbly flow regime based upon flow visualization using a high-speed video camera. A database of local time-averaged void fraction, bubble velocity, interfacial area concentration, and bubble Sauter mean diameter are acquired throughout the entire pipe cross-section using a four-sensor conductivity probe for nine flow conditions. To investigate the evolution of the flow, measurements are made at axial locations of 44, 116, and 244 diameters downstream of the inlet. Using this database, the effects of gas flow rate, liquid flow rate, and development length on the local and area-averaged two-phase flow parameters are presented. From the local profiles, it is found that highly turbulent liquid flow conditions cause the void fraction profile to become more uniform with increasing development length through a turbulent mixing process which counters the effect of buoyancy. Bubble interactions are also observed to play a significant role in the evolution of the flow such that the area-averaged void fraction and interfacial area concentration can have different axial trends.

Experiments in Cap-Bubbly Two-Phase Flows for Two-Group IATE Development

In the two-group interfacial area transport equation (IATE) used to calculate the interfacial area concentration (ai), bubbles are categorized into two groups. Namely, group-I consists of spherical/distorted bubbles, and group-II consists of cap/slug/churn-turbulent bubbles. Robust models for the major bubble interaction mechanisms that cause the transition from purely one-group to two-group flows are essential to the dynamic closure of the two-fluid model with the two-group IATE. Therefore, the present study seeks to establish an experimental database in cap-bubbly flows that highlights this transition to support model development. A four-sensor conductivity probe is used to obtain measurements of local time-averaged two-phase flow parameters, including the void fraction and ai, in vertical-upward air-water two-phase flows in a 5.08-cm pipe. Four flow conditions are investigated at ⟨jf⟩ = 2 m/s with increasing ⟨jg⟩ to study the generation and growth of group-II bubbles. Characteristic features of the local void fraction and ai distributions are discussed. Additionally, axial development of area-averaged void fraction and ai that is indicative of exchange between the bubble groups is presented.

Experiments on the Effects of a Spacer Grid in Air-Water Two-Phase Flow

Understanding the effects of spacer grids on the coolant flow through a nuclear reactor core is required for best-estimate design and analysis of the plant. The impact of a spacer grid on two-phase flows is of particular importance because the geometric effects of the grid can alter the two-phase flow structure and, consequently, the mass, momentum, and energy transfer characteristics. Therefore, a scaled separate-effects test facility is constructed to investigate the effects of a spacer grid on the hydrodynamics of air-water two-phase flow through a rod bundle. The test facility is scaled to maintain hydrodynamic and geometric similarity to single- and two-phase flows in a conventional pressurized water reactor and to facilitate detailed local measurements of two-phase flow parameters around the simulant fuel rods with a four-sensor conductivity probe. This paper presents measurements of local time-averaged two-phase flow parameters acquired upstream and downstream of the spacer grid with the conductivity probe in a representative subchannel of a 1×3 rod bundle for eight flow conditions. Characteristic features of the development of the two-phase flow parameters along the test section are discussed.

Considerations in the Practical Application of the Multisensor Conductivity Probe for Two-Phase Flow

This study investigates two issues in the practical application of the local conductivity probe for two-phase flow measurements. First, the effects of signal “ghosting,” an electrical interference inherent to multiplexing data acquisition systems, on the measured two-phase flow parameters are examined. A revised conductivity probe circuit is proposed to remove the effects of ghosting. The characteristics of signal ghosting are investigated experimentally with a specialized conductivity probe that enables concurrent acquisition of ghosted and unghosted signals within the same flow condition. It is demonstrated that ghosting causes bubble velocity measurements that are artificially high and, consequently, artificially low interfacial area concentration measurements that depend on sampling frequency and sensor impedance. The revised circuit successfully eliminates this variability. Second, the sensitivity of measured two-phase flow parameters to increasing data acquisition sampling frequency is investigated experimentally. Measurements are acquired at incrementally increasing sampling frequencies with a four-sensor conductivity probe in 13 vertical-upward air-water two-phase flow conditions with superficial liquid and gas velocities ranging from 1.00 to 5.00 m/s and 0.17 to 2.0 m/s, respectively. It is found that the void fraction and average bubble velocity are insensitive to the sampling frequency, while the detected number of bubbles and interfacial area concentration can demonstrate a strong dependence. Considerations for selecting appropriate sampling frequencies in different flow conditions are discussed.

Model of bubble velocity vector measurement in upward and downward bubbly two-phase flows using a four-sensor optical probe

The knowledge of bubble behaviors is of considerable significance for a proper understanding and modeling of two-phase flows. To obtain the information on the bubble motion, a novel model was developed, by which the bubble velocity vector can be directly calculated from six time intervals measured with a four-sensor probe. The measurements of local bubble velocity vector and void fraction were performed in both upward and downward bubbly flows by using a four-sensor optical probe. The area-averaged void fraction and bubble velocity obtained from the probe agree well with those measured by other cross-calibration methods, and the measurement errors are within 15% under various flow conditions. Experimental results of the bubble velocity vector reveal that the bubble lateral migration may be suppressed in upward flows, but be strengthened in downward flows as the liquid flow rate increases. Also, with an increase in gas flow rate, the bubble velocity distribution varies into the power–law profile in upward flows, but into an off-center peak profile in downward flows. In addition, the void fraction shows a core peak distribution at low void fraction for downward flows, but a wall peak distribution for upward flows. However, when the void fraction is relatively high, it displays an off-center peak distribution for downward flows but a core peak distribution for upward flows.

Evaluation of interfacial area transport equation in vertical bubbly two-phase flow in large diameter pipes

The introduction of interfacial area transport equation (IATE) has greatly improved the overall performance of two-fluid model due to the fact that the IATE can predict the interfacial area concentration (IAC) more accurately. However, models in the source and sink terms of IATE that are developed for predicting bubble coalescence and breakup are mainly based on small diameter pipe flows. Since the two-phase flow in a large diameter pipe is characterized by its multi-dimensional nature, the IATE should be confirmed before being applied to large pipe flows. From this point of view, local measurements in air–water bubbly flow systems in a large pipe with 101.6mm diameter were performed by using four-sensor optical probes. The radial profiles of the void fraction, IAC, bubble Sauter mean diameter and interfacial velocity were obtained at two axial locations of z/D=2 and 29. The simplified one-dimensional, steady-state, adiabatic one-group IATE with eight sets of bubble coalescence and breakup models was evaluated against the present experimental data and that from the literatures. The evaluation results showed that the Sun et al. (2004a) model is the best one for large diameter pipes. This model can well reflect the interfacial transfer mechanisms and can provide a reasonable prediction in general. Besides, the models of Smith et al. (2012a) and Ishii and Kim (2001) are also recommended due to their relative good performance in the prediction of IAC. Further work should be undertaken to develop a new bubble coalescence and breakup model with extra consideration of the multi-dimensional flow behavior in large pipes, if necessary.

Comparison of local interfacial characteristics between vertical upward and downward two-phase flows using a four-sensor optical probe

To model the interfacial transfer terms more accurately in two-fluid model as well as to further comprehend the intrinsic mechanism for downward two-phase flows, more information that involves local interfacial parameters is required. The local interfacial characteristics in upward and downward bubbly flows were investigated separately in a 50.8mm inner-diameter round pipe. A four-sensor optical probe was used in the measurement of local interfacial parameters, including void fraction, interfacial area concentration (IAC), bubble frequency, interfacial velocity and Sauter mean diameter. The radial profiles of these parameters in downward flows were presented and compared with that in upward flows. In general, the void fraction shows a core-peaked distribution for the downward flow at low void fraction, but shows a wall-peaked distribution for the upward flow; while at high void fraction, it has an off-center-peaked distribution for the downward flow but a core-peaked distribution for the upward flow. Also, under relative high void fraction conditions, the profile of Sauter mean diameter presents a pronounced maximum in the channel center for the upward flow whereas near the channel wall for the downward flow. Additionally, with an increase in the gas flow rate, the flat profiles of interfacial velocity transform to power-law shapes in the upward flows but to that with the velocity increasing along the radius for the downward flows.

Experiments on geometric effects of 90-degree vertical-upward elbow in air water two-phase flow

This study investigates the geometric effects of a 90-degree vertical-upward elbow on local two-phase flow-parameters in an air–water system, and develops an experimental database for interfacial area transport modeling. The experimental facility is constructed from 5.08cm inner diameter acrylic pipes and includes vertical and horizontal sections interconnected by a 90-degree vertical glass elbow. The elbow has a radius of curvature of 15.24cm and is installed at L/D=63 from the inlet. A four-sensor conductivity probe is used to measure time-averaged local two-phase flow parameters including: void fraction, bubble velocity, interfacial area concentration, and bubble frequency at ten axial locations along the test section. It is observed that the bubbles moving through the vertical-upward elbow are entrained by the secondary flow leading to a bimodal distribution in bubbly flow conditions. For the flow conditions investigated within the study, this bimodal distribution occurs regardless of the bubble distribution upstream of the elbow. It is found that the change in bubble distribution downstream of the elbow is strongly correlated to the dissipation of the elbow effects. Furthermore, the dissipation characteristics as well as the length of dissipation region for the vertical-upward elbow are found to be a strong function of the liquid-phase flow rate.

Local interfacial parameter distribution for two-phase flow under rolling conditions using a four-sensor optical probe

As a typical marine condition, rolling motion has a significant effect on a two-phase flow system, which has attracted increasing attention. However, the local characteristics of a two-phase flow system in rolling motion are seldom reported, which makes the two-fluid model difficult to apply in such a situation. More information that involves local interfacial parameters is required for further comprehending the intrinsic mechanism by which the interfacial area transport equation becomes applicable under a rolling condition. An experimental investigation of two-phase flow in a rolling condition was conducted by using a four-sensor optical probe. Parameters such as the local void fraction, interfacial area concentration (IAC) and bubble frequency were obtained. To obtain interfacial parameters at a rolling angle position, the averaged values in a small angle interval around the chosen position were used to represent the local parameters at that site, and in the same way, one can obtain variations of all of those parameters over a complete rolling cycle. The experimental results showed that the void fraction, IAC and bubble frequency present a periodic variation with the rolling motion. Additionally, the peak positions of these parameters, regardless of whether they are correct at the maximum angle, significantly depend on the rolling period, the rolling amplitude, and the gas flow rate. They might occur earlier in the cycle as the rolling period or amplitude increases or as the gas flow rate increases.

Experimental Investigation on the Effects of a Spacer Grid on Single- and Two-Phase Flows

Experiments are performed in a scaled 1x3 rod bundle adiabatic air-water test facility to investigate the effects of a spacer grid on singleand two-phase flows. A four-sensor conductivity probe is used to obtain detailed measurements of local time-averaged two-phase flow parameters, including the void fraction and interfacial area concentration, throughout the flow cross-section at four axial locations. The local two-phase flow data indicates that the spacer grid causes redistribution of the bubbles. In the transition from bubbly to slug flows, the spacer grid is found to promote bubble coalescence. In the slug to churn-turbulent transition, however, the grid breaks up the larger bubbles, causing an increase in the interfacial area concentration across the spacer grid. Additionally, local velocity measurements in single-phase liquid flow are performed with a laser Doppler anemometer to investigate the change in the turbulence structure across the grid. The axial turbulence intensity measurements show the influence of the spacer grid dimples, indicating an increased mixing effect from these structures.

Spherical-bubble-based four-sensor probe signal processing algorithm for two-phase flow measurement

This paper describes a newly-developed complete four-sensor probe signal processing algorithm for local instantaneous 3-dimensional bubble velocity vector, local instantaneous bubble diameter, local instantaneous interfacial normal unit vector, local interfacial area concentration (IAC) in a multi-dimensional two-phase flow by utilizing the spherical bubbles in the flow. The newly-developed algorithm has opened a way for the measurement of 3-dimensional bubble velocity vector and bubble diameter with a four-sensor probe. The newly-developed algorithm also has overcome the weakness of the conventional four-sensor probe signal processing algorithm, in which the interfaces passing through the tips of the probe sensors are supposed to be planar, even in the small bubble measurement for the local IAC. The newly-developed algorithm can keep a consistency with the conventional algorithm in measuring large bubbles since the newly-developed algorithm is reduced to the conventional algorithm for the local IAC, the local instantaneous interfacial normal unit vector and the local instantaneous 3-dimensional interfacial displacement velocity vector when the bubble size becomes to be much larger than the size of the four-sensor probe and the interface of the bubble can be locally viewed as 2 tangent planes. The bubbles in practical two-phase flows are classified into spherical bubbles and non-spherical bubbles according to a newly-introduced bubble deviation coefficient from spherical shape (namely an aspheric shape factor). Based on the spherical bubbles, the newly-developed signal processing algorithm can perform the measurement for the local parameters in two-phase flows. The newly-developed signal processing algorithm was applied to the measurements in a vertical air–water multi-dimensional two-phase flow in a large-diameter pipe as an example and was checked against the other measurement methods. The comparisons were very satisfactory and showed that the newly-developed four-sensor probe signal processing algorithm can perform the local measurements for the practical multi-dimensional two-phase flow.

Measurements of liquid-phase turbulence in gas–liquid two-phase flows using particle image velocimetry

Liquid-phase turbulence measurements were performed in an air–water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method-–planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas–liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high-fidelity codes for multi-phase flows.

Local interfacial velocity measurement method using a four-sensor probe

This paper presents a theoretical foundation of the measurement methods for the instantaneous local interfacial velocity vector and the time-averaged local interfacial area concentration using a four-sensor probe for multi-dimensional two-phase flow measurements. The measurement method is derived based on a large bubble assumption that locally views the front and rear interfaces of an approaching bubble as two tangent planes. The newly-derived method provides an explicit expression for the instantaneous local interfacial velocity vector using a four-sensor probe. The derived method for the time-averaged local interfacial area concentration was found to be in the same form as that proposed by Kataoka et al. (1986) [1]. The derived method was applied to the practical two-phase flow measurements in a vertical pipe with an inner diameter of 200mm. The measured void fraction and interfacial velocity component in the axial direction were checked against the void fraction measurement using differential pressure gages and the superficial gas velocity measurement using gas flow meters, respectively. The measured interfacial velocity components in the radial and circumferential velocity components were found to be close to zero, which is in accordance with the fact that no stable flow of bubbles with certain horizontal velocity component exists in a vertical circular pipe. The measured interfacial area concentrations showed reasonable radial distributions in the pipe. The good agreements in the practical measurements suggest that the newly-derived method can reasonably measure interfacial velocity vector and interfacial area concentration in multi-dimensional two-phase flows.

Local gas and liquid parameter measurements in air–water two-phase flows

Local measurements of flow parameters for the gas and liquid phases are conducted in an air–water two-phase flow loop. The test section is a vertical circular pipe with an inner diameter of 50mm and a height of 3.2m. The local measurements are performed at two elevations, namely 10 and 32 pipe diameters downstream from the test section inlet. The gas-phase measurements are carried out using four-sensor conductivity probes. The data taken from the probes at different radial locations are processed using a signal-processing program to yield radial profiles of the void fraction, bubble velocity, bubble number frequency, and interfacial area concentration. The measurements of the liquid-phase velocity are made using a particle image velocimetry (PIV) system with an optical phase separation method, namely, planar laser-induced fluorescence (PLIF). Raw PIV images are acquired by a CCD camera using fluorescent particles and an optical filter. An image pre-processing scheme is developed and applied to the raw PIV images to minimize the residual signals due to the presence of bubble surfaces. A systematic uncertainty introduced by multiple refractions on the circular test section wall and a square viewing box is discussed and the measurement accuracy can then be improved by compensating for this uncertainty source. A statistical cross-correlation algorithm provided by LaVision Inc. is adopted to determine the liquid-phase velocity and its fluctuations. The local liquid-phase velocity is compared with data available in the literature. This relatively high spatial resolution data set for both the gas and liquid phases can be used for two-phase computational fluid dynamic (CFD) model development and benchmarking.

Optimal design of a four-sensor probe system to measure the flow properties of the dispersed phase in bubbly air–water multiphase flows

This paper presents a systematic investigation on the design and development of a four-sensor probe system to be used for air–water multiphase flow measurements. A mathematical model is presented which can be used to determine the optimum axial separation of the front sensor with respect to three rear sensors within a four sensor probe system. This system can be used to measure flow properties of the dispersed phase in bubbly air–water flows accurately. Paper also presents a sensitivity analysis to determine the minimum sampling frequency requirements in the data collection process, so that associated errors in various output parameters can be minimized, for the given values of sensors co-ordinates. A particularly novel feature of this paper is development of a unique digital signal processing scheme to enable the accurate computation of different flow characteristics.This paper also presents validation of four-sensor probe measurements from a flow visualization and measurement system which relies on using two high speed cameras mounted orthogonally. The results obtained from validation experiments show very high degree of similarity in measured flow variables from the two systems. This indicates that the four-sensor probe system developed in this study can be used with confidence to measure parameters of a dispersed multiphase flow. The flow characteristics obtained from the four-sensor probe system when used in a multiphase flow system are also presented. The results indicate a unique flow pattern corresponding to bubbles of different sizes in air–water flows.

The development of two-phase flow structures in air–water planar bubble jets

Air–water two-phase upflow experiments are performed in a 200×10mm2 rectangular duct to study the multi-dimensional development of two-phase interfacial structures. The air flow is injected into the test section with a uniform and a center peaked inlet profile for nine different flow rates covering bubbly, cap-turbulent and churn-turbulent flows. A four-sensor conductivity probe is used to measure local void fraction, interfacial area concentration, bubble velocity and Sauter mean diameter at three cross sections in a 3m long test section. Experimental results show considerable axial and lateral developments of two-phase flow parameters in the test section. For certain conditions, the inlet profile has a significant effect on the phase distribution, phase velocity, interfacial structure and bubble interaction mechanisms. These results indicate that the conventional flow regime concept may not be applicable to developing flows and flows with a spatial distribution. Instead, the interfacial area transport equation (IATE) provides a dynamic and quantitative description of two-phase flow structures which can better serve the two-fluid model. A comparison of predictions by a one-dimensional (1D) two-group IATE and experimental data shows good agreement for uniform inlet flows. For center peaked flows, the 1D IATE systematically underestimates the interfacial area concentration of group 1 bubbles but overestimates that of group 2 bubbles. This is due to not accounting for the covariance terms in the 1D model such that certain bubble interaction mechanisms such as shearing-off and turbulent impact are under predicted. The pairing of uniform and center peaked planar jet experiments in this study present a unique benchmark for understanding separate effects in two-phase gas–liquid vertical flows.

Large probe arrays for measuring mean and time dependent local oil volume fraction and local oil velocity component distributions in inclined oil-in-water flows

Arrays of dual-sensor and four-sensor needle conductance probes have been used to measure the mean and time dependent local properties of upward inclined, bubbly oil-in-water flows (also known as dispersed oil-in-water flows) in a 153mm diameter pipe. The flow properties that were measured were (i) the local in-situ oil volume fraction α; (ii) the local oil velocity uo in the axial direction of the pipe (the Z direction); and (iii) the local oil velocity uY in the direction from the lower side of the inclined pipe to its upper side (the Y direction). Oil velocities in the X direction (orthogonal to the Y and Z directions) were found to be negligible. For all of the flow conditions investigated it was found that the mean value of α varied from a maximum value at the upper side of the inclined pipe to a minimum value at the lower side, and that the rate of decrease of this mean value of α with distance in the −Y direction became greater as the pipe inclination angle θ from the vertical was increased. It was also found that the mean value of uo was greatest at the upper side of the inclined pipe and decreased towards the lower side of the inclined pipe, the rate of decrease with distance in the −Y direction again becoming greater as θ was increased. For θ=45o, a water volumetric flow rate Qw=16.38m3h−1, an oil volumetric flow rate Qo=6.0m3h−1 and using a sampling period T=0.05s over a total time interval of 60s, it was found that at the upper side of the inclined pipe the standard deviation in uo was 31.6% of the mean value of uo. Furthermore for T=0.05s, θ=30o, Qw=16.38m3h−1 and Qo=6.0m3h−1 it was found that the standard deviation in the cross-pipe oil velocity component uY was approximately equal to the standard deviation in the axial velocity component uo. These large temporal variations in the local flow properties have been attributed to the presence of large scale Kelvin–Helmholtz waves which intermittently appear in the flow. It is believed that the techniques outlined in this paper for measuring the standard deviation of local flow properties as a function of the sampling period T will be of considerable value in validating mathematical models of time dependent oil–water flows. It should be noted that the principal focus of this paper is on the measurement techniques that were used and the methods of data analysis rather than the presentation of exhaustive experimental results at numerous different flow conditions.

Water temperature effect on upward air-water flow in a vertical pipe: Local measurements database using four-sensor conductivity probes and LDA

Experimental work was carried out to study the effects of temperature variation in bubbly, bubbly to slug transition. Experiments were carried out in an upward air-water flow configuration. Four sensor conductivity probes and LDA techniques was used together for the measurement of bubble parameters. The aim of this paper is to provide a bubble parameter experimental database using four-sensor conductivity probes and LDA technique for upward air-water flow at different temperatures and also show transition effect in different temperatures under the boiling point.

Experimental study of non-uniform inlet conditions and three-dimensional effects of vertical air–water two-phase flow in a narrow rectangular duct

To study the three-dimensional interfacial structure development in vertical two-phase flow, air–water upflow experiments were performed in a rectangular duct. Various non-uniform two-phase profiles were created by injecting air from individually controlled spargers at the duct inlet into uniformly injected water flow. A four-sensor conductivity probe was used to measure local void fraction, interfacial area concentration, bubble velocity and Sauter mean diameter at three axial locations to record the development of two-phase parameters. Experimental results showed that the lateral development across the wider dimension of the duct was significant with a non-uniform inlet profile when compared to a uniform inlet profile. It is postulated that lift, wall and turbulent forces are the major contributors to the lateral distribution of the two-phase interfacial structures making this an useful experiment for benchmarking three-dimensional two-fluid models. In examining the interfacial area, the shearing-off of group 1 bubbles (defined as the smaller spherical and distorted bubbles) from the skirt region of group 2 bubbles (defined as the bigger cap and churn bubbles), the coalescence of group 2 bubbles due to wake entrainment, and random collision are the major source and sink mechanisms of interfacial area concentration.