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Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article  
Ravichandra Jagannath, Sally Bane and Razi Nalim
J. Fluids Eng   doi: 10.1115/1.4040015
Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and a quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment.
TOPICS: Computer simulation, Turbines, Waves, Rotors, Flow (Dynamics), Pressure, Blades, Boundary-value problems, Ducts, Unsteady flow, Leakage, Flow turning, Friction, Energy transformation, Heat transfer, Conservation laws (Physics), Gates (Closures), Angular momentum
research-article  
Fu Xiaolong, Li Deyou, Wang Hongjie, Zhang Guanghui, Li Zhenggui, Wei Xianzhu and Qin Daqing
J. Fluids Eng   doi: 10.1115/1.4040038
Complex energy conversion and energy dissipation occur in pump-turbines during the load rejection process. However, the underlying fluid mechanism is not clear. In order to solve these problems, in this study, a three-dimensional transient turbulent flow in a pump-turbine, with clearance during the load rejection process, was simulated using the method of coupling of the rigid rotor motion with flow and dynamic mesh technology. The simulated rotational speed shows good agreement with the experimental data. Most of the differences of rotational speed between simulations and experiments are very small and lower than 5%. Based on the numerical simulation, the energy conversion process, loss distribution, and flow mechanism in a pump-turbine were analyzed using the method of coupling of the entropy production analysis with the flow analysis. The results indicate that the load rejection process of a pump-turbine is an energy-dissipation process where the energy is converted among various energy forms. After load rejection, the hydraulic loss in the reverse pump process distributes primarily in the stay/guide vanes, the vaneless space and near draft tube inlet. While, the hydraulic losses in the runaway process and the braking process are distributed mainly in the elbow section of the draft tube, the clearance of runner, and the vaneless space. The hydraulic losses are mainly caused by viscous dissipation effects of the vortex flows, including the flow separation vortices, the shedding vortices of flow wake, the secondary flow and the backflow.
TOPICS: Pump turbines, Stress, Flow (Dynamics), Energy dissipation, Energy conversion, Clearances (Engineering), Vortices, Braking, Flow separation, Vortex flow, Guide vanes, Engineering simulation, Pumps, Rotors, Fluids, Turbulence, Computer simulation, Entropy, Simulation, Transients (Dynamics), Wakes
research-article  
Jin-yuan Qian, Zhi-xin Gao, Bu-zhan Liu and Zhi-jiang Jin
J. Fluids Eng   doi: 10.1115/1.4040037
Globe valve is widely used in numerous industries, and its driving energy consumption accounts for high percentage of the whole piping system. In order to figure out novel globe valves with low energy consumption, the pilot control globe valve (PCGV) is proposed, which is made up of a main valve and a pilot valve. By the pressure difference of fluid itself, the opened/closed status of the main valve can be controlled by the pilot valve, which can save driving energy and shorten the response time. In order to fit PCGV in an angle displaced piping system, the pilot control angle globe valve (PCAGV) is developed. In this paper, with validated numerical methods, both steady and transient simulations focusing on the valve core diameter, the single/multi orifices and their diameters and arrangements located on the valve core bottom are presented. The results show that the pressure difference increases with the increase of the valve core diameter and the decrease of the orifice diameter, and large orifice diameter (d > 12 mm) should be avoided in case that the valve cannot be opened. As for the multi orifices, it can be treated as a single orifice that has similar cross-sectional area. Meanwhile, the opening time of the main valve also increases with the increase of the valve core diameter correspondingly. Besides, fitting formula of pressure difference calculation depending on the inlet velocity and the valve core diameter is obtained, which is a power-law relationship.
TOPICS: Fluid dynamics, Valves, Pressure, Energy consumption, Orifices, Piping systems, Fittings, Fluids, Simulation, Transients (Dynamics), Engineering simulation, Numerical analysis
research-article  
Jian Fei Zhang, Shuang Wang, Hongyan Li and Zhiguo Qu
J. Fluids Eng   doi: 10.1115/1.4040016
Wire and nonparallel plate electrode-type electrostatic air accelerators have attracted significant interest. The physical process involved in using accelerators is complicated. Moreover, mechanisms are unclear, especially for accelerators with double- and multi-wire electrodes. In this study, the 2D model of a wire-nonparallel plate-type accelerator validated by experiments is established with an infinite element method. Onset voltage, average current, and outlet average velocity are analyzed with respect to different parameters. Onset voltage is derived by the proposed quadratic regression extrapolation method. Moreover, current is affected by interference and discharge effects, while velocity is also influenced by the suction effect. For the single-wire electrode, high wind speed can be obtained by either increasing channel slope or placing the wire near the entry section. For the double-wire electrode, velocity can be further increased when one of the wires is placed near the inlet and the distance between the two wires is widened. Comparatively, the velocity of the three-wire electrode is higher with larger gaps between wires and stronger discharge effect. The highest velocity is obtained by the four-wire electrode. Comparisons indicate that higher velocity can be obtained with weaker interference effect, stronger suction effect, and intensified discharge effect. Optimum parameter combinations are considered by the Taguchi method. Consequently, velocity can be enhanced by more than 39% after optimization compared with the reference design.
TOPICS: Flow (Dynamics), Wire, Optimization, Electrodes, Suction, Wind velocity, Design, Taguchi methods
research-article  
Seyed Sobhan Aleyasin, Nima Fathi, Mark F. Tachie, Peter Vorobieff and Mikhail Koupriyanov
J. Fluids Eng   doi: 10.1115/1.4040031
The aim of this study is to examine the effects of Reynolds number (Re = 6000 - 20000), on mean and turbulent quantities as well as turbulent structures in the near and intermediate regions of equilateral triangular and round sharp contraction jets. The results show shorter potential core length, faster growth of turbulence intensity and diffusion of turbulent structures to the centerline of the triangular jets; implying enhanced mixing in the near field of these jets. On the other hand, the velocity decay and jet spread rates are higher in the round jets. The obtained data in the round jets show that the jet at Re = 6000 has the most effective mixing, while an increase in Reynolds number reduces the mixing performance. In the triangular jets, however, no Reynolds number effects were observed on the measured quantities including the length of the potential core, the decay and spread rates, the axis-switching locations and the value of local Reynolds number. In addition, the asymptotic values of the relative turbulence intensities on the jet centerline are almost independent of the Reynolds number and geometry. The ratios of transverse and spanwise Reynolds stresses are unity except close to the jet exit where the flow pattern in the major plane of the triangular jet deflects towards the flat side. POD analysis revealed that turbulent structures in minor and major planes have identical fractional kinetic energy. The integral length scales increased linearly with the streamwise distance with identical slope for all the test cases.
TOPICS: Reynolds number, Jets, Turbulence, Kinetic energy, Flow (Dynamics), Diffusion (Physics), Geometry, Stress
research-article  
Fei Huang, Shuqing Li, Yanlin Zhao and Yong Liu
J. Fluids Eng   doi: 10.1115/1.4039945
This paper focuses on the lateral jetting commencing points associated with the peak pressure when an arc-curved jet impacts flat, concave, convex and inclined solid surfaces, respectively. A theoretical method based on a shock wave background is used to establish models for these situations, which indicate that the critical radius for the initiation of lateral jetting is dependent on the combined actions of the jet velocity, surface shape and surface angle. Arbitrary Lagrangian-Eulerian formulations are then used to model the process of arc-curved jets impacting varied solid surfaces. The numeric simulation results are found to be in good agreement with the theoretical models.
TOPICS: Pressure, Shock waves, Jets, Shapes, Simulation results
research-article  
Kaushik Kudtarkar, Michael Johnson, Patricia Iglesias, Thomas W. Smith and Michael Schertzer
J. Fluids Eng   doi: 10.1115/1.4039946
This investigation demonstrates microfluidic synthesis of monodisperse hydrogel beads with controllable electromechanical properties. Hydrogel beads were synthesized using aqueous monomer solutions containing difunctional macromer, ionic liquid monomer, and photoinitiator. Electromechanical properties of these beads were measured at compression ratios up to 20% to examine their potential use in vibrational energy harvesters. Bead stiffness decreased dramatically as water content increased from 19% to 60%. As water content and compression ratio increased, electrical permittivity of beads increased, while resistivity decreased. As ionic liquid monomer concentration increased from 0% to 4%, relative permittivity increased by 30% - 45% and resistivity decreased by 70% - 80%.
TOPICS: Hydrogels, Water, Electrical properties, Compression, Electrical resistivity, Energy harvesting, Microfluidics, Stiffness
research-article  
Quang Dang Le, Riccardo Mereu, Giorgio Besagni, Vincenzo Dossena and Fabio Inzoli
J. Fluids Eng   doi: 10.1115/1.4039908
In this paper, a computational fluid dynamics model of flashing flow, which considers the thermal non-equilibrium effect, has been proposed. In the proposed model, based on the two-phase mixture approach, the phase-change process depends on the difference between the vaporization pressure and the vapour partial pressure. The thermal non-equilibrium effect has been included by using ad-hoc modelling of the boiling delay. The proposed model has been applied to the case of two-dimensional axisymmetric convergent-divergent nozzle, which is representative of well-known applications in nuclear and energy engineering applications (e.g., the primary flow in the motive nozzle of ejectors). The numerical results have been validated based on a benchmark case from the literature and have been compared with the numerical results previously obtained by different research groups. The proposed approach has shown a good level of agreement as regards the global and the local experimental fluid dynamic quantities. In addition, sensitivity analyses have been carried out concerning (a) grid independency, (b) turbulence modelling approaches, (c) near-wall treatment approaches, (d) turbulence inlet parameters and (e) semi-empirical coefficients. In conclusion, the present paper aims to provide guidelines for the simulation of flash boiling flow in industrial applications.
TOPICS: Flow (Dynamics), Flashing, Modeling, Nozzles, Computational fluid dynamics, Boiling, Pressure, Equilibrium (Physics), Turbulence, Simulation, Energy engineering, Fluids, Ejectors, Delays, Sensitivity analysis
research-article  
Jiandong Yang, ZhenHua Wan, Liang Wang and DeJun Sun
J. Fluids Eng   doi: 10.1115/1.4039862
An effective boundary potential has been proposed to solve non-periodic boundary condition (NPBC) of hybrid method. The optimized hybrid method is applied to investigate the influences of the channel height and solid-liquid interaction parameters on slip characteristics of Couette flows in micro/nanochannels. By changing the channel height, we find that the relative slip lengths show the obvious negative correlation with the channel height and fewer density oscillations are generated near the solid wall in the larger channel height. Moreover, we continue to investigate the solid-liquid interaction parameters, including the solid-liquid energy scales ratio (C1) and solid-liquid size scales ratio (C2). The results show that the solid-liquid surface changes from hydrophobic to hydrophilic with the increase of C1, the arrangement of liquid particles adjacent to the solid particles is more disorganized over the hydrophobic solid-liquid surface compared with the hydrophilic surface, and the probability of the liquid particles appear near the solid particles becomes smaller. Meanwhile, the relative slip lengths are minimum when the liquid and solid particles have the same diameter. Furthermore, the relative slip lengths follow a linear relationship with the shear rate when the solid-liquid interaction parameters change. The plenty computational time has been saved by the present hybrid method compared with the full molecular dynamics simulation (FMD) in this paper.
TOPICS: Particulate matter, Boundary-value problems, Probability, Molecular dynamics simulation, Shear rate, Density, Oscillations, Flow (Dynamics)
research-article  
Solkeun Jee, Jongwook Joo and Ray-Sing Lin
J. Fluids Eng   doi: 10.1115/1.4039865
An efficient large-eddy simulation (LES) approach is investigated for laminar-to-turbulent transition in boundary layers. This approach incorporates the boundary-layer stability theory. Primary instability and sub-harmonic perturbations determined by the boundary-layer stability theory are assigned as forcing at the inlet of the LES computational domain. This LES approach reproduces the spatial development of instabilities in the boundary layer, as observed in wind tunnel experiments. Detailed linear growth and nonlinear interactions that lead to the H-type breakdown are well captured and compared well to previous direct-numerical simulations. Requirements in the spatial resolution in the transition region are investigated with connections to the resolution in turbulent boundary layers. It is shown that the sub-grid model used in this study is apparently dormant in the overall transitional region, allowing the right level of the growth of small-amplitude instabilities and their nonlinear interactions. The sub-grid model becomes active near the end of the transition where the length scales of high-order instabilities become smaller in size compared to the given grid resolution. Current results demonstrate the benefit of the boundary-layer forcing method for the computational cost reduction.
TOPICS: Simulation, Boundary layers, Resolution (Optics), Stability, Turbulence, Boundary layer turbulence, Wind tunnels, Large eddy simulation
research-article  
Pedro A. de S. Matos, Luiz Gilberto Barreta and Cristiane Aparecida Martins
J. Fluids Eng   doi: 10.1115/1.4039863
A LIF-based nitric-oxide flow-tagging technique was applied to measure both velocity and NO lifetime in a hypersonic shock tunnel from two experimental test runs. The results were supported by an analytical profile proposed in this paper that provides a way to correct displaced measurements due to unknown systematic error sources. This procedure provided velocities with discrepancies lower than 3% for a total of five measurements, and lower than 2% when compared with those obtained from a linear fit. Additionally, the comparison between the proposed and experimental profiles allowed us to obtain the fluorescence NO lifetime from only one image.
TOPICS: Fluorescence, Flow (Dynamics), Air flow, Shock (Mechanics), Errors, Tunnels
Technical Brief  
Dr. V Babu
J. Fluids Eng   doi: 10.1115/1.4039864
A simple procedure for calculating the the pressure at the onset and termination of condensation shocks that occur in steam nozzles and steam turbine blade passages is presented. In addition, the location of the termination of the condensation shock with reference to the throat location is also predicted. The procedure is based entirely on thermodynamic and gas dynamic considerations and without using a model for droplet nucleation and growth and the nozzle profile. The only input required is the stagnation condition at the inlet to the nozzle. The procedure requires the solution of a system of algebraic equations which can be accomplished quite easily. Calculations have been carried out for a several inlet stagnation conditions and the predictions are compared with available experimental data. The agreement is seen to be reasonable considering the simplicity of the procedure.
TOPICS: Shock (Mechanics), Condensation, Nozzles, Blades, Steam, Steam turbines, Algebra, Drops, Nucleation (Physics), Pressure
research-article  
Zdenek Travnicek and Zuzana Brouckova
J. Fluids Eng   doi: 10.1115/1.4039792
A novel variant of a synthetic jet actuator (SJA) has been designed, manufactured and tested. The novelty consists in a bio-inspired nozzle whose oscillating lip is formed by a flexible diaphragm rim. The working fluid is air, and the operating frequency is 65 Hz. The proposed SJA was tested by three experimental methods: phase-locked visualization of the nozzle lips, hot-wire anemometry, and momentum flux measurement using a precision scale. The results demonstrate advantages of the proposed SJA, namely, an increase in the momentum flux by 18% compared with that of a conventional SJA.
TOPICS: Actuators, Nozzles, Biomimetics, Momentum, Fluids, Wire, Diaphragms (Mechanical devices), Diaphragms (Structural), Visualization, Experimental methods
research-article  
Teng Zhou, Yongbo Deng, Hongwei Zhao, Xianman Zhang, Liuyong Shi and Sang Woo Joo
J. Fluids Eng   doi: 10.1115/1.4039709
Viscoelastic solution is encountered extensively in microfluidics. In this work, the particle movement of the viscoelastic flow in the contraction-expansion channel is demonstrated. The fluid is described by the Oldroyd-B model, and the particle is driven by dielectrophoretic (DEP) forces induced by the applied electric field. A time dependent multiphysics numerical model with the thin electric double layer (EDL) assumption was developed, in which the Oldroyd-B viscoelastic fluid flow field, the electric field and the movement of finite-size particles are solved simultaneously by an Arbitrary Lagrangian-Eulerian (ALE) numerical method. By the numerically validated ALE method, the trajectories of particle with different sizes were obtained for the fluid with the Weissenberg number (Wi) of 1 and 0, which can be regarded as the Newtonian fluid. The trajectory in the Oldroyd-B flow with Wi=1 is compared with that in the Newtonian fluid. Also, trajectories for different particles with different particle sizes moving in the flow with Wi=1 are compared, which proves that the contraction-expansion channel can also be used for particle separation in the viscoelastic flow. The above results for this work provide the physical insight into the particle movement in the flow of viscous and elastic features.
TOPICS: Flow (Dynamics), Separation (Technology), Particulate matter, Fluids, Electric fields, Computer simulation, Trajectories (Physics), Microfluidics, Numerical analysis, Viscoelastic fluids
research-article  
Hyunjin Yang, Surya P. Vanka and Brian G. Thomas
J. Fluids Eng   doi: 10.1115/1.4039793
The Eulerian-Eulerian two-fluid model (EE) is a powerful general model for multiphase flow computations. However, one limitation of the EE model is that it has no ability to estimate the local bubble sizes by itself. In this work, we have combined the Discrete Phase model (DPM) to estimate the evolution of bubble sizes with the Eulerian-Eulerian model. In the DPM, the change of bubble size distribution is estimated by coalescence and breakup modeling of the bubbles. The time-varying bubble distribution is used to compute the local interface area between gas and liquid phase, which is then used to estimate the momentum interactions such as drag, lift, wall lubrication and turbulent dispersion forces for the EE model. In this work, this newly-developed hybrid model (EEDPM) is applied to compute an upward flowing bubbly flow in a vertical pipe and the results are compared with previous experimental work. The EEDPM model is able to reasonably predict the locally different bubble size distributions and the velocity and gas fraction fields. On the other hand, the standard EE model without the DPM shows good comparison with measurements only when the prescribed constant initial bubble size is accurate and does not change much. Parametric studies are implemented to understand the contributions of bubble interactions and volumetric expansion on the size change of bubbles quantitatively. The results show that coalescence is larger than other effects, and naturally increases in importance with increasing gas fraction.
TOPICS: Turbulence, Bubbly flow, Bubbles, Turbulent diffusion, Modeling, Pipes, Computation, Drag (Fluid dynamics), Multiphase flow, Momentum, Lubrication, Fluids
research-article  
Rakhitha Udugama and Sukalyan Bhattacharya
J. Fluids Eng   doi: 10.1115/1.4039708
This paper uses eigen expansion technique to describe electro-osmotic effect on unsteady intrusion of a viscous liquid driven by capillary action in a narrow channel. It shows how the dynamics can be manipulated by imposing an electric field along the flow-direction in presence of free charges. Similar manipulation can generate controlled transiency in motion of a complex fluid in a tube by non-destructive forcing leading to efficient rheological measurement. Existing theories analyze similar phenomena by accounting for all involved forces among which the viscous contribution is calculated assuming a steady velocity profile. However, if the transport is strongly transient, a new formulation without an underlying quasi-steady assumption is needed for accurate prediction of the time-dependent penetration. Such rigorous mathematical treatment is presented in this article where an eigen function expansion is used to represent the unsteady flow. Then, a system of ordinary differential equations is derived from which the unknown time-dependent amplitudes of the expansion are determined along with the temporal variation in encroached length. The outlined methodology is applied to solve problems with both constant and periodically fluctuating electric field. In both cases, simplified and convenient analytical models are constructed to provide physical insight into numerical results obtained from the full solution scheme. The detailed computations and the simpler reduced model corroborate each other verifying accuracy of the former and assuring utility of the latter. Thus, the theoretical findings can render a new rheometric technology for effective determination of fluid properties.
TOPICS: Fluids, Electric fields, Dynamics (Mechanics), Capillarity, Flow (Dynamics), Rheology, Transients (Dynamics), Eigenfunctions, Differential equations, Computation, Unsteady flow, Accounting
research-article  
Zhonglu Lin, Dongfang Liang and Ming Zhao
J. Fluids Eng   doi: 10.1115/1.4039712
This study investigates the flow mediated interaction between two vibrating cylinders of the same size immersed in an otherwise still fluid. The master cylinder carries out forced vibration, while the slave cylinder is elastically-mounted with one degree of freedom along the center-line between the two cylinders. We examined the stabilized vibration of the slave cylinder. In total, 6269 two-dimensional cases were simulated to cover the parameter space, with the a fixed Reynolds number of 100, the structural damping factor of the slave cylinder ranging from 0 to 1.4, the mass ratio of the slave cylinder ranging from 1.5 to 2.5, the initial gap ratio ranging from 0.2 to 1.0, the vibration amplitude ratio of the master cylinder ranging from 0.025 to 0.1, and the vibration frequency ratio ranging from 0.05 to 2.4. We found that the vibration amplitude of the slave cylinder is highly sensitive to damping when the damping coefficient is small. The two cylinders' vibration is in antiphase at low frequencies but in phase at high frequencies. The phase of the slave cylinder changes abruptly at resonance when it has little damping, but the phase change with the frequency becomes increasingly gradual with increasing damping. With a non-zero damping factor, the maximum vibration amplitude of the slave cylinder is inversely correlated with its mass ratio. The response of the slave cylinder is explained by examining the pressure distribution and velocity field adjacent to it.
TOPICS: Flow (Dynamics), Damping, Cylinders, Vibration, Resonance, Pressure, Fluids, Reynolds number, Oscillating frequencies, Degrees of freedom
research-article  
Ming Liu, Lei Tan and Shuliang Cao
J. Fluids Eng   doi: 10.1115/1.4039714
Prewhirl regulation by inlet guide vanes (IGVs) has been proven as an effective method for operation regulation of centrifugal pumps. By contrast, the influence of the geometry of IGVs on operation stability of centrifugal pump remains unknown. The pressure fluctuations and flow patterns in a centrifugal pump without and with 2D or 3D IGVs are investigated numerically at 1.0Qd, 0.6Qd, and 1.2Qd. RNG k-? turbulence model is used as turbulence model, and fast Fourier transform method is used to analyze the pressure fluctuations. The dominant frequency of pressure fluctuations in impellers is either the rotational frequency fi or twice thereof for pumps without and with IGVs at three flow rates, while the dominant frequency is constantly the blade passing frequency in volute. For 1.0Qd, the comparison of pumps without IGVs indicates that the maximum amplitude of pressure fluctuations at fi in pumps with 2D IGVs is decreased by an average of 22.2%, and the amplitude is decreased by an average of 44.9% in pumps with 3D IGVs. The IGVs mainly influence the pressure fluctuations at fi but indicate minimal influence at 2fi. For 0.6Qd, the comparison of pumps without IGVs denotes that the maximum amplitudes of pressure fluctuations at fi in pumps with 2D or 3D IGVs both increase; the maximum increase is 2.01%. For 1.2Qd, the comparison of pumps without IGVs indicates that the maximum amplitudes of pressure fluctuations at fi in pumps with 2D or 3D IGVs both decrease; the maximum decline is 15.9%.
TOPICS: Pressure, Fluctuations (Physics), Centrifugal pumps, Geometry, Inlet guide vanes, Pumps, Flow (Dynamics), Turbulence, Impellers, Stability, Blades, Fast Fourier transforms
research-article  
Numa J. Bertola, Hang Wang and Hubert Chanson
J. Fluids Eng   doi: 10.1115/1.4039715
The entrainment, breakup and interplay of air bubbles were observed in a vertical, two-dimensional supported jet at low impact velocities. Ultra-high-speed movies were analyzed both qualitatively and quantitatively. The onset velocity of bubble entrainment was between 0.9 and 1.1 m/s. Most bubbles were entrained as detached bubbles from elongated air cavities at the impingement point. Explosion, stretching and dejection mechanisms were observed for individual bubble breakup, and the bubble interaction behaviors encompassed bubble rebound, "kiss-and-go", coalescence and breakup induced by approaching bubble(s). The effects of jet impact velocity on the bubble behaviors were investigated for impact velocities from 1.0 to 1.36 m/s, in the presence of a shear flow environment.
TOPICS: Explosions, Shear flow, Bubbles, Jets, Cavities, Air entrainment
research-article  
Chaari Majdi, Seibi Abdennour C., Ben Hmida Jalel and Fekih Afef
J. Fluids Eng   doi: 10.1115/1.4039710
Simplifying assumptions and empirical closure relations are often required in existing two-phase flow modeling based on first-principle equations, hence limiting its prediction accuracy and in some instances compromising safety and productivity. State-of-the-art models used in the industry still include correlations that were developed in the sixties, whose prediction performances are at best acceptable. To better improve the prediction accuracy and encompass all pipe inclinations and flow patterns, we propose in this paper an artificial neural network (ANN)-based model for steady-state two-phase flow liquid holdup estimation in pipes. Deriving the best input combination among a large reservoir of dimensionless Pi groups with various fluid properties, pipe characteristics, and operating conditions, is a laborious trial-and-error procedure. Thus, a self-adaptive genetic algorithm (GA) is proposed in this work to both ease the computational complexity associated with finding the elite ANN model and lead to the best prediction accuracy of the liquid holdup. The proposed approach was implemented using the Stanford multiphase flow database (SMFD), chosen for being among the largest and most complete databases in the literature. The performance of the proposed approach was further compared to that of two prominent models, namely a standard empirical correlation-based model and a mechanistic model. The obtained results along with the comparison analysis confirmed the enhanced accuracy of the proposed approach in predicting liquid holdup for all pipe inclinations and fluid flow patterns.
TOPICS: Flow (Dynamics), Artificial neural networks, Steady state, Pipes, Two-phase flow, Databases, Errors, Genetic algorithms, Fluids, Safety, Reservoirs, Multiphase flow, Modeling, Fluid dynamics

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