Visualization Of Multiphase Flow Research Articles

Simultaneous flow and particle measurements for multiphase flows in hydraulic engineering: A review and synthesis of current state

While multiphase flows are abundant in both natural environments and engineering applications, their analysis and quantification present challenges. In particular, simultaneously measuring the flow field and quantifying particle behavior pose many challenges. Methods based on Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) principles have been used in the last two decades to measure flow fields and dispersed (particle) phases, respectively. Despite the extensive application of these principles to multiphase flow, there are numerous approaches and techniques used to synchronize and combine PIV and PTV measurements. Combined PIV and PTV data acquisition also requires consideration of phase discrimination to obtain distinct data for the fluid and dispersed phases. In the literature, various methods have been proposed and applied to achieve phase discrimination. This review paper aims to consolidate and classify various phase discrimination techniques used in specialized applications in hydraulic engineering. These methods are categorized into optical (spectral, temporal, and hybrid) and post-processing methods, with a particular emphasis on their applicability within the realm of hydraulic engineering. Moreover, this review expands on several emerging PIV/PTV technologies and applications, where the combination of equipment and algorithms has led to significant strides in the non-intrusive measurement of multiphase flow. By consolidating and critically evaluating current methods for particle discrimination, this paper aims to enhance the scientific community's understanding of simultaneous phase velocity measurements, thereby setting the stage for advancements in multiphase flow visualization techniques.

X-Ray Flow Visualization: Techniques and Applications

Abstract Multiphase flows, defined as a discrete phase in a continuous fluid phase, are found in many natural, industrial, and consumer flows, from rain fall and avalanches to petroleum processing and fuel combustion to cookie dough mixing and pasta making. Many of these flows have an interior that is hidden from optical flow measurements, and intrusive probes can modify the flows of interest. Noninvasive measurement techniques, like X-ray flow visualization, provide a means to visualize and quantify the flow conditions in areas obstructed to visual access. Additionally, X-rays are unlikely to modify or alter the flow of interest. This paper reviews various X ray flow visualization techniques, including those using X-rays from tube sources, electron guns, and synchrotron sources. X-ray fundamentals are first reviewed. Then, various X ray imaging techniques are highlighted, and applications of those techniques are summarized using several multiphase flow examples. Advantages and disadvantages of each technique are provided and the unique flow features that can be captured with X-ray flow visualization are summarized. As detailed, X-ray flow visualization is a powerful tool for multiphase flow visualization and characterization, particularly when the flow of interest has limited or no optical access.

A digital twin of electrical tomography for quantitative multiphase flow imaging

Multiphase flow is ubiquitous in nature, industry and research, and accurate flow imaging is critical to understanding this complex phenomenon. Electrical tomography (ET) is a promising technique for multiphase flow visualization and characterization which provides a non-invasive and non-radiative way to unravel the internal physical properties at high temporal resolution. However, existing ET-based multiphase flow imaging methods are inadequate for quantitative imaging of multiphase flows due to inversion errors and limited ground truth data of fluid phases distribution. Here we report a digital twin (DT) framework of ET to address the challenges of real-time quantitative multiphase flow imaging. The proposed DT framework, building upon a synergistic integration of 3D field coupling simulation, model-based deep learning, and edge computing, allows ET to dynamically learn the flow features in the virtual space and implement the model in the physical system, thus providing excellent resolution and accuracy. The proposed DT framework is demonstrated using electrical capacitance tomography (ECT) of a gas-liquid two-phase flow. It can be readily extended to a broader range of tomography modalities, scenarios, and scales in biomedical, energy, and aerospace applications.

A COMSOL Multiphysics study on block-to-block interactions in naturally fractured reservoirs

In fractured reservoirs, block-to-block interactions (re-infiltration and capillary continuity) significantly affect gravity drainage performance. Re-infiltration controls the drainage rate. This process may significantly delay oil production. Despite the numerous attempts to study the re-infiltration process, there is still much controversy about the factors that affect this phenomenon. This work focused on designing two sets of 2D models aimed at improving the simulation and visualization of multiphase flow in fractured porous media while providing a more realistic understanding of the pore-scale phenomena and flow communication between matrix-fracture and matrix-matrix. The simulation was performed in COMSOL Multiphysics in the single-porosity model. Moreover, the impact of different parameters such as rock type, physical properties of the fluids, tilt angle, matrix block height and area, fracture opening, and matrix blocks porosity-permeability on gravity drainage performance, especially block-to-block interactions, has been examined. Besides investigating the effect of each parameter, combined effects of those parameters have likewise been investigated. To rank the most critical observed parameters on the re-infiltration process, the grey relational analysis was applied. The results of this analysis showed the physical properties of the fluids have the most influence on re-infiltration. In addition, it was demonstrated that tilt angle reduces the degree of re-infiltration in deviated blocks. Also, a combination of oil-wet rocks and high irreducible water saturation results in a decrease in oil recovery, a delay in production, and a decrease in the degree of re-infiltration. Additionally, fractures with small openings and taller blocks promote greater re-infiltration; however, their impact on ultimate recovery is not significant. The findings of this study can help for a better understanding of the relative influence of different reservoir parameters on gravity drainage performance and block-to-block interactions. • Visualization and simulation of block-to-block interaction in fractured porous media using COMSOL multiphysics. • Providing a new insight on the relative importance of different reservoir parameters in block-to-block interaction. • Using grey relational analysis (GRA) to rank the influence of parameters on the re-infiltration process.

Experimental study on multiphase flow in 3D-printed heterogeneous, filled vugs

The fractured-vuggy carbonate reservoir possesses the characteristics of a highly discrete distribution of fractures and vugs, a wide scale range, and the coexistence of free flow and porous flow. However, it also exhibits a high degree of filling media in vugs, including chemical sedimentation, carried fillings and collapsed fillings, which poses challenges for studying the mechanism of enhanced oil recovery (EOR) in filled fracture-vug reservoirs. In this paper, 3D printing technology is utilized to construct heterogeneous, filled models. With a multiphase flow visualization platform, displacement experiments of different injection-production methods, including water injection, gas injection and the co-injection of water and gas, are conducted to elucidate the mechanisms of EOR. It is found that the lower is the gas injection rate or the higher is the water injection rate, the higher is the recovery factor for a horizontal filled vug. For a vertical filled vug, gravity exerts a greater influence on the gas swept area, but inertial forces dominate fluid flow when the water injection log Ca exceeds −2.68. In addition, in a displacement experiment of a simultaneous injection of gas and water, the gas-water mixing zone appears until log Ca ≥ −4.38 (gas) and log Ca ≥ −2.68 (water). Then, the synergistic gas-water effect displaces the oil phase in the filled medium with a higher recovery rate. Therefore, the displacement of gas and water co-injection is preferred over sequential injections, and the injection velocity of gas and water should be compatible. • 3D printing technology is utilized to construct heterogeneously-filled vug media. • Displacement experiments of different injection-production methods are conducted to investigate mechanisms of EOR. • The gas-water mixing zone appears when log Ca ≥ −4.38 (gas) plus log Ca ≥ −2.68 (water). • The synergistic gas-water effect displaces the oil phase in the filled medium with a higher recovery rate. • The co-injection of gas-water is preferred, and the velocity of gas and water should be compatible.

Visual identification of oscillatory two-phase flow with complex flow patterns

We present an approach based on computer vision and machine learning methods to identify two-phase flow with complex flow patterns in oscillatory conditions. A visualization experiment bench was designed, constructed, and used to simulate the actual reciprocating motion of the cooling gallery inside the piston of low-speed diesel engines. The results of our proposed approach show that the feature vectors extracted from the optical flow images provides a valuable reference for the velocity vectors in two-phase flow. We show that it is possible to identify oscillatory two-phase flow videos with respect to Reynolds numbers from 10568 to 31704 using a Bayesian Network classifier, with the best accuracy of 94%. The approach purposed in this paper can not only be used to present the validating sources for numerical simulation results, but also be widely applied in the visualization of multiphase flow, which is a key area to be developed on the basic research of heat transfer systems.

X-Ray Flow Visualization in Multiphase Flows

The use of X-ray flow visualization has brought a powerful new tool to the study of multiphase flows. Penetrating radiation can probe the spatial concentration of the different phases without the refraction, diffraction, or multiple scattering that usually produce image artifacts or reduce the signal-to-noise ratio below reliable values in optical visualization of multiphase flows; hence, X-ray visualization enables research into the three-dimensional (3D) structure of multiphase flows characterized by complex interfaces. With the commoditization of X-ray laboratory sources and wider access to synchrotron beam time for fluid mechanics, this novel imaging technique has shed light onto many multiphase flows of industrial and environmental interest under realistic 3D configurations and at realistic operating conditions (high Reynolds numbers and high volume fractions) that had defied study for decades. We present a broad survey of the most commonly studied multiphase flows (e.g., sprays, fluidized beds, bubble columns) in order to highlight the progress X-ray imaging has made in understanding the internal structure and multiphase coupling of these flows, and we discuss the potential of advanced tomography and time-resolved and particle tracking radiography for further study of multiphase flows.

Smooth Particle Hydrodynamic and URAN Visualization of Multiphase Flow

Significant research is being conducted in the simulation of fluid flows due to the increase in employing the physics of the fluid flow to either commercial, in-house or open source codes. The analysis of the fluid flow is mainly based on the Lagrangian or the Eulerian approach. Many of the simulation codes employ the Eulerian approach due to its simplicity. These codes are based on several numerical techniques and yet few benchmarks have been conducted. However, the codes which employ the Lagrangian approach seem to be promising and may accurately simulate fluid flow phenomena. In this paper, a comparative analysis of the Lagrangian and Eulerian approach is investigated for a water droplet in a tank. The velocity field and the total pressure of the fluid are generated for the simulation by employing Ansys Fluent for the Eulerian approach and DualPhysics for the Lagrangian approach. The fluid structure and the fluid flow development are compared in order to assess the capability of each approaches in analysing the investigated fluid flow. This study may play a significant role on the importance of employing the Lagrangian approach for fluid flows where complex fluid structure occurs.

Imaging of compositional gradients during in situ emulsification using X-ray micro-tomography

The rate of emulsification in surfactant/oil/water systems is influenced by transport of chemicals and mixing of the fluid phases. In porous media applications, complex flow regimes are generated due to three-dimensional connectivity and irregular cross-sections of the pores facilitating the mixing for emulsification. The properties of the resulting emulsified phase depend on the interplay of flow, mixing and emulsification kinetics of the surfactant/oil/water system. Emulsification can be relatively quick. Direct visualization of the process and compositional gradients in three-dimensional pore space during flow requires imaging at few seconds time intervals.In this study, a flow unit was integrated in a synchrotron beamline-based fast X-ray computed micro-tomography set-up. Non-destructive three-dimensional visualization of multi phase flow inside a porous rock at flow conditions became viable. An oil saturated rock sample was first flooded with water, followed by surfactant solution to mobilize the remaining oil by miscible displacement. The sample was continuously imaged during injection; the scans were made at time intervals of 7–60 s.The presence of an emulsified phase in addition to the oil and the aqueous phases required a more advanced image processing workflow compared to the workflows used for the immiscible fluid systems. A newly developed image processing technique was adopted; the grey levels in the images were correlated with the local oil content in the emulsified fluid regions. The visual extractions of the pore space showed that the emulsification occurred within seconds. Compositional gradients were observed in the emulsified phase as the injected surfactant solution reached the remote locations in the pore space. While a significant fraction of the oil was displaced within few seconds, the compositional gradients persisted over several millimeter length for several minutes, illustrating a sequence of mobilization and solubilization of the oil phase. The ability to interpret such compositional gradients in real time in porous space brings capability to study interfacial phenomena in applications where in situ emulsification occurs under flow.

2D MODELLING OF A SENSOR FOR ELECTRICAL CAPACITANCE TOMOGRAPHY IN ECTSIM TOOLBOX

Electrical capacitance tomography is used to visualize a spatial distribution of dielectrical permittivity of materials placed in a tomographic sensor. An image is reconstructed from measurements of mutual capacitances of electrodes placed around the examined volume. This technique is characterized by very high temporal resolution – it is possible to achieve even few thousands of images per second. One of drawbacks of the method is low spatial resolution. Electrical capacitance tomography is mainly used in industry, e.g. for multiphase flow visualization. One of important elements of a tomographic system is a sensor which parameters influence quality of measurements and therefore affects quality of reconstructed images. In the Division of Nuclear and Medical Electronics a Matlab toolbox called ECTsim was developed. It is used for modelling of sensors, simulations of electrical field and image reconstruction. In this article we present the latest improvement which is modelling of a sensor using algebra of sets. Using primitive elements like rectangle and sector of a ring it is possible to perform operations like union, intersection and difference of two elements with a designed language. With such tools it is easy to prepare complex models of tomographic sensors which have different geometries. In this paper we show two models of sensors with different geometry in order to show how ECTsim solves forward problem.

A two-angle far-field microscope imaging technique for spray flows

Backlight imaging is frequently used for the visualization of multiphase flows, where with appropriate microscope lenses, quantitative information on the spray structure can be attained. However, a key issue resides in the nature of the measurement which relies on a single viewing angle, hence preventing imaging of all liquid structures and features, such as those located behind other fragments. This paper presents results from an extensive experimental study aimed as a step forward towards resolving this problem by using a pair of high speed cameras oriented at 90 degrees to each other, and synchronized to two high-speed diode lasers. Both cameras are used with long distance microscope lenses. The images are processed as pairs allowing for identification and classification of the same liquid structure from two perspectives at high temporal (5 kHz) and spatial resolution (∼3 μm). Using a controlled mono-disperse spray, simultaneous, time-resolved visualization of the same spherical object being focused on one plane while de-focused on the other plane 90 degrees to the first has allowed for a quantification of shot-to-shot defocused size measurement error. An extensive error analysis is performed for spheroidal structures imaged from two angles and the dual angle technique is extended to measure the volume of non-spherical fragments for the first time, by ‘discretising’ a fragment into a number of constituent ellipses. Error analysis is performed based on measuring the known volumes of solid arbitrary shapes, and volume estimates were found to be within ∼11% of the real volume for representative ‘ligament-like’ shapes. The contribution concludes by applying the ellipsoidal method to a real spray consisting of multiple non-spherical fragments. This extended approach clearly demonstrates potential to yield novel volume weighted quantities of non-spherical objects in turbulent multiphase flow applications.

Development of numerical evaluation method for fluid dynamics effects on jet breakup phenomena in BWR lower plenum

The jet breakup phenomena of the molten cores during a severe accident are affected by some complicated structures, such as control rod guide tubes, instrument guide tubes, and core support plate, in the lower plenum of the boiling water reactors (BWRs). A multi-phase computational fluid dynamics approach combined with experiments is considered to be the best way to estimate the jet breakup phenomena in the BWR lower plenum, and a numerical analysis method has been developed based on the interface tracking method code TPFIT (Two-Phase Flow simulation code with Interface Tracking). The analysis method developed was applied to single-/multi-channel experiments for verification and validation in this study. Furthermore, results from the numerical analysis were compared to the experimental results obtained using the multi-phase flow visualization technique using a high-speed camera and the particle image velocimetry method. As a consequence, it is found that the simulation method developed in this study can qualitatively simulate the jet breakup phenomena in the complicated structure.

Evaluation of 3D Mapping Experimental Non-Intrusive Methods for Multiphase Flows

The present contribution focuses on the evaluation of non-intrusive 3D mapping experimental methods for the investigation of multiphase flows during tank sloshing. This problem is a key issue for launchers and satellites since the feeding in propellants has to be ensured during flight and manoeuvres. At first, an extensive survey of non-intrusive experimental techniques of interest for multiphase flows has been carried out. This task has accounted for new innovative methods developed for space and non-space applications with a focus on the methods used in medicine and other fields such as ultrasound techniques. A particular care has been given to electrical and ultrasonic tomography techniques since they are both non-intrusive, non-invasive, low cost, fast and simple to operate, and suitable for real time measurements. Electrical tomography techniques have demonstrated convincing capabilities for multiphase flow visualization and present numerous advantages for industrial processes and multiphase flow measurements. Ultrasound experimental techniques are extensively used in medicine for a wide range of investigations. They are also largely used for material analysis and fluid mechanics. As a consequence since several years, ultrasound tomography has been applied to multiphase flows. Application of the method to annular, sludge, slug and bubbly flows has demonstrated the potential of this technique for multiphase flow investigations. Additionally, in the context of launchers this technique presents an advantage in term of safety. Using the available results, the advantages and disadvantages of ultrasonic and electrical methods have been identified and this leads to the conclusion that the ultrasonic tomography possesses the best potential for the final application. Finally, using the available experimental results obtained using ultrasound tomography for the mapping of multiphase flows, numerical simulations have been performed to proceed to their reconstruction. This provides a cross-check between the experimental data and the numerical predictions in order to assess the suitability of the techniques for future studies.

W121005 混相流れを視る : プロセス・トモグラフィの応用([W12100]設計工学・システム部門,米国機械学会日本支部企画,Monozukuri by 1DCAE～夢を形に～)

W121005 混相流れを視る : プロセス・トモグラフィの応用([W12100]設計工学・システム部門,米国機械学会日本支部企画,Monozukuri by 1DCAE～夢を形に～)

Dynamic Visualization Approach of the Multiphase Flow Using Electrical Capacitance Tomography

Identifying the flow patterns is vital for understanding the complicated physical mechanisms in multiphase flows. For this purpose, electrical capacitance tomography (ECT) technique is considered as a promising visualization method for the flow pattern identification, in which image reconstruction algorithms play an important role. In this paper, a generalized dynamic reconstruction model, which integrates ECT measurement information and physical evolution information of the objects of interest, was presented. A generalized objective functional that simultaneously considers the spatial constraints, temporal constraints and dynamic evolution information of the objects of interest was proposed. Numerical simulations and experiments were implemented to evaluate the feasibility and efficiency of the proposed algorithm. For the cases considered in this paper, the proposed algorithm can well reconstruct the flow patterns, and the quality of the reconstructed images is improved, which indicates that the proposed algorithm is competent to reconstruct the flow patterns in the visualization of multiphase flows.

Design of Parallel Electrical Resistance Tomography System for Measuring Multiphase Flow

ERT (electrical resistance tomography) is effective method for visualization of multiphase flows, offering some advantages of rapid response and low cost, so as to explore the transient hydrodynamics. Aiming at this target, a fully programmable and reconfigurable FPGA (field programmable gate array)-based Compact PCI (peripheral component interconnect) bus linked sixteen-channel ERT system has been presented. The data acquisition system is carefully designed with function modules of signal generator module; Compact PCI transmission module and data processing module (including data sampling, filtering and demodulating). The processing module incorporates a powerful FPGA with Compact PCI bus for communication, and the measurement process management is conducted in FPGA. Image reconstruction algorithms with different speed and accuracy are also coded for this system. The system has been demonstrated in real time (1400 frames per second for 50 kHz excitation) with signal-noise-ratio above 62 dB and repeatability error below 0.7%. Static experiments have been conducted and the images manifested good resolution relative to the actual object distribution. The parallel ERT system has provided alternative experimental platform for the multiphase flow measurements by the dynamic experiments in terms of concentration and velocity.

Creation of a dual-porosity micromodel for pore-level visualization of multiphase flow

This paper describes the creation and testing of an etched-silicon micromodel that has the features and characteristics of a dual-porosity pore system mimicking those found in certain carbonate reservoir rocks. This micromodel consists of a two-dimensional (2D) pore network etched into a silicon wafer with a bonded glass cover that permits direct visual examination of pore-level displacement mechanisms and pore-network characteristics during fluid flow experiments. The approach began by creating a mosaic of images from a carbonate thin section of a sample with both high porosity and permeability using a scanning electron microscope (SEM) in back-scattered mode (BSE). Connections based on high-pressure mercury injection data were made to ensure that the 2D connectivity in the imaged pore structure was representative of the three dimensional (3D) pore network of the carbonate sample. Microelectronic photolithography techniques were then adapted to create micromodels for subsequent fluid flow experiments. Micromodel surfaces were made oil- or water-wet by various techniques. One of the main advantages of having a representative carbonate dual-porosity micromodel is the ability to observe pore-level mechanisms of multiphase flow and interpret petrophysical properties. Another advantage is that multiple replicates are available with identical conditions for each new experiment. Micromodel utility is demonstrated here through the measurement of porosity, permeability, fluid desaturation patterns, and recovery factors.

Visualization of multi phase flow

Visualization of multi phase flow

A local reconstruction method for low-energy gamma-ray computed tomography system

In the application of computed tomography (CT) system to industrial multiphase flow visualization, the number of projections is usually limited, and the detector elements are sparsely arranged, the limited number of measurement data has put the validity of the conventional reconstruction algorithms in jeopardy. Although improved iterative reconstruction methods have been developed to compensate for the lack of projection data, the imaging quality is still inadequate for the reconstruction of relatively complicated flow regime. To overcome this problem, we propose a novel local reconstruction method based on the Landweber algorithm and apply it to a low-energy gamma-ray CT system for two-phase flow measurement. The object to be reconstructed is partitioned into a number of sub-regions and local reconstruction is implemented on each sub-region utilizing only gamma-rays passing through that region. The feasibility is demonstrated in both numerical simulations and prototype experiments. Comparison between the proposed method and the Landweber iterative algorithm shows that the former has obviously improved the imaging quality.

Special Issue on “Multi-Dimensional Visualization of Multiphase Flow”

Special Issue on “Multi-Dimensional Visualization of Multiphase Flow”