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The virus diffusion in a ventilated room with the droplets produced by coughing and breathing are presented by the Lagrangian model. When the human body is located in the middle of the room with two locations of AC, in front of and behind the human body, three angles of Air Conditioning (AC) gate are applied 0°, 30°, and 60° to show droplet particle diffusion in the room in these cases. Three types of coughing velocity profiles were selected, real human coughing, sinusoidal cough, and cough jet with one velocity profile of breathing as a step function to cover the inhaling and exhaling cycle. The simulation results show that the uncovered standing in the middle of the room, are more susceptible to infection for the bouncy and forced flow around the human body. Droplet particle moves in the room as a random diffusion and it is very sensitive to the thermal load inside the room, generally depends on the bouncy force and pressure force due to convection heat transfer. when the AC location at the opposite direction of coughing flow, the droplet travels a distance of about 3 m, 2.85 m, and 2.75 m for real cough, sinusoidal cough, and cough jet respectively. While the droplet travel distance is about 3.1 m, 3.2 m, and 2.9 m when the AC location is at the same direction of coughing flow. Finally, the adopted CFD modeling was also used to show the effects of different AC locations on coughing, breathing particle droplets distribution in different indoor spaces, such as buildings, hospitals, and public transports, Also, showed good visual demonstration and representation of the real physical processes.

Microchannels are important devices to improve the heat exchange in several engineering applications as heat, ventilation and air conditioning, microelectronic cooling, power generation systems and others. The present work performs a numerical study of a microchannel with two trapezoidal blocks subjected to laminar flows, aiming to analyze the influence of the boiling process on the geometric configuration of the microchannel. Constructal Design and Exhaustive Search are used for the geometrical evaluation of the blocks. The Mixture multi-phase model and the Lee phase change model were both employed for the numerical simulation of the boiling process. In this study, the influence of the height and higher width of the first block (H11/L11) over the heat transfer rate and pressure drop for different magnitudes of the ratio between the lower width and higher width (L12/L11) was investigated. It is considered water in monophase cases and water/vapor mixture for multiphase flow. Two different Reynolds numbers (ReH = 0.1 and 10.0) were investigated. Results indicated that, for the present thermal conditions, the consideration of boiling flows were not significant for prediction of optimal configurations. Results also showed that in the cases where the boiling process was enabled, the multi-objective performance was higher than in the cases without boiling, especially for ReH = 0.1.

A mechanistic model has been applied for the prediction of corrosion rate in multiphase (water–oil-gas) flow regimes. This is due to inadequacies of existing models to adequately address a wide variety of corrosion dependent parameters with special emphasis on multiphase flow parameters. This model takes into account; water cut, volumetric phase fraction of oil and gas, temperature, pressure, other data collected relating to the pipe age, sand particle deposit, CO2 partial pressure, flow velocity, pH, chloride contents, mass transfer coefficients, and hydrogen sulfide. The applied model results show well above 91 percent prediction accuracy, while the prediction error ranges between 0.022 and 0.045 percent. When predicted results compared actual value (experimental data) with DeWaard and Milliams’ model; used in the oil and gas industries, it showed good agreement. It is seen that the resulting model produced an R2 value of 0.91 in comparison to 0.53, the value for Dewaard and Milliams’. It is obvious from numerical simulation that the multiphase flow parameters have major effects on the entire rate of corrosion of oil and gas multiphase flow pipelines. Finally, this research concluded by showing the developed model performance and comparison was made with numerical results. It is expected that the outcome of this research will be of significant help for the strengthening of the application of mechanistic models for predicting corrosion rate. This model will be useful for oil and gas industries worldwide for accurate prediction of corrosion rate.

Knowledge of wellbore multiphase flow characteristics is important for early gas invasion identification and treatment, especially in oil-based drilling fluid. The wellbore multiphase flow law in downhole dual-gradient drilling (DDGD) is more complex than that in conventional single-gradient drilling. There was no relevant literature report at present. In this paper, considering the synergistic feedback relationship of multiphase flow, interphase mass transfer, and wellbore temperature, a fully transient wellbore multiphase flow model was established based on oil-based drilling fluid in deepwater DDGD. The model also coupled the variable temperature–mass flows caused by the dynamic transfer of hollow glass balls and formation gas. The bubble interface mass transfer theory was adopted to describe the interphase mass transfer rate. The model was verified through the experimental measurement data. The calculated results indicated that the dynamic transfer of hollow glass balls varied the wellbore pressure gradient and flow rate in DDGD, resulting in a sudden decrease in gas fraction and gas solubility along the flow direction at the separator. Additionally, the transient interphase mass transfer and wellbore temperature had large impact on the wellbore multiphase flow behaviors. Moreover, the model based on bubble interface mass transfer theory could more accurately characterize the development of the wellbore multiphase flow. This research could provide a certain theoretical basis for the detection and treatment of gas invasion in deepwater DDGD.

A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.

Bubbles in electrolysis exhibit significant complexities that greatly affect mass transport at gas-evolving electrodes. This renders disentangling the relevant effects through experiments an extremely tedious task. Therefore, in this thesis we utilize numerical simulations to unravel the controlling mechanisms of mass transfer at gas-evolving electrodes. In chapter 1, we combine the in-situ experiments with numerical simulations to study the effect of single-phase natural convection on the growth and dissolution of bubbles adhering to the electrode. Untangling the effect of diffusion and natural convection, we observe that the experimentally measured bubble evolution can only be accurately described once the flow induced by buoyancy forces is taken into account in addition to the diffusive transport. Furthermore, we reveal the effect of design parameters such as bubble spacing and their arrangement in a clustered network on the convective pattern and the resultant bubble dynamics. In chapter 2, we investigate micro- and macro-convection caused by bubble growth and rise in the electrolyte solution. First, we quantify the hydrogen and electrolyte transport at the electrode by defining an effective Grashof number which accounts for buoyancy forces of gas-in-liquid dispersion. Our findings highlights the dominance of two-phase buoyancy-driven convection over other mass transfer mechanisms. Next, we quantify hydrogen transport to the bubble and derive an expression for gas-evolution efficiency, which is key in determining the bubbles evolution and hence the following mass transfer processes in such systems. In chapter 3, we look into the downward dissolution dynamics of carbon dioxide in a cylindrical water barrier employing experiments and simulations. We reveal that convection causes front convolutions and steepens the gradients nearby. This leads to enhanced diffusive flux across the interface and hence faster propagation of the front. Our findings offer broader insight into the secure storage of CO2 in carbon capture and storage technologies.

Solid-liquid mixing plays a significant role in crystallization, suspension polymerization, leaching, solid-catalyzed reaction and adsorption. In this study, a computational fluid dynamic (CFD) model was developed for solid-liquid mixing in a cylindrical tank equipped with a top-entering impeller. The multiple reference frame (MRF) technique, k-ε model and Eulerian-Eulerian approach were employed to simulate the impeller rotation, turbulent flow and multiphase flow, respectively. The effects of impeller speed, solid concentration, particle size, solid density and impeller clearance on the mixing performance of four different impellers (A310, marine propeller, pitched blad turbine and A320) were investigated. The CFD results were in good agreement with experimental data measured using electrical resistance tomography (ERT). In order to investigate the mixing quality in this study, the impeller speed required for maximum homogeneity, clouding height, and just-suspended impeller speed were investigated.

Bubbly flow in bubble column reactors promotes mixing necessary for many chemical processes. We show that if superhydrophobic-coated material is introduced into a bubble column, there can be a substantial difference in gas holdup and earlier initiation of churn-turbulent flow which can alter larger-scale mixing without a need to change the superficial gas velocity. Addition of superhydrophobic surface can also cause bubbles to (directly or indirectly assisted by the surface) escape faster to the free surface resulting in a reduced void fraction (i.e., reduced gas holdup). As the flow becomes optically opaque at few percent gas phase volume fraction, we utilize two dual plane wire mesh sensors to obtain velocity profiles and bubble size distributions, in addition to the traditional pressure and level based gas holdup measurements to calculate average phase fraction. Additionally, a custom build photon-counting dual energy threshold X-ray computed tomography system is employed to get a higher resolution measurement of the time average phase fraction non-intrusively. We report satisfactory agreement between these techniques with differences arising for understood reasons, and use the insight thus yielded to discuss the effect of superhydrophobic surfaces on bubble column flow dynamics.

A multiphase, transient, horizontal, Taylor-Couette flow has been investigated numerically. This flow governs thermal performance of self-contained drum motor (SCDM) drive systems. These drive systems are extensively used with conveyor belt systems, employed in many industrial and commercial applications. Thermal performance of the SCDM drive system is governed by heat transfer within multiphase flow of air and oil. This flow is confined within a horizontal annular space between two concentric cylinders. The outer cylinder is the drum. It rotates and rejects heat to the atmosphere. The inner cylinder is the outer surface of the motor. It is stationary and subjected to a constant heat flux. This heat is generated within the electric motor, gearbox, and oil viscous dissipation. Numerical simulations have been carried out using ANSYS-CFX. Transient flow and thermal fields have been investigated, starting from an initial stationary state until a quasi-steady state is reached. The effect of drum rotational speed and oil level on thermal performance of the SCDM drive system has been investigated. The study covers a range of rotational speeds from 0 to 150 rpm, oil level from 0%, (i.e., 100% air-filled) to 100%. Numerical results have been validated using experimental data. The optimum oil level has been determined which gives the lowest possible overall maximum SCDM system temperatures. This optimum oil level depends on the drum rotational speed. Results indicated that the 100% oil-filled case does not provide the best thermal performance. The Nusselt number around the inner cylinder has been correlated as a function of rotational Reynolds number and oil level. The developed correlation can be used as a design tool. This tool is to optimize system thermal performance by determining the optimum oil level at a given rotational speed.

A multiphase flow 3D numerical simulation method employing the coupled volume of fluid (VOF) and level set model is established to study the reactive absorption of CO2 by the monoethanolamine (MEA) aqueous solution in a falling film microchannel. Based on the flow-reaction-mass transfer model of the MEA-CO2 system in the falling film microchannel, the enhancement effect of the Marangoni convection in this reactive absorption process is analyzed. The enhancement factor of the Marangoni convection obtained in this work is in good agreement with experimental results in the literature. With consideration of the absorption ratio as well as the enhancement effect of the Marangoni convection, the influence of different MEA concentrations on absorption of CO2 is investigated. Furthermore, the appropriate MEA concentration for absorption enhanced by the Marangoni convection is acquired.

Hypothesis Imbibition of a fluid into a porous material involves the invasion of a wetting fluid in the pore space through piston-like displacement, film and corner flow, snap-off and pore bypassing. These processes have been studied extensively in two-dimensional (2D) porous systems; however, their relevance to three-dimensional (3D) natural porous media is poorly understood. Here, we investigate these pore-scale processes in a natural rock sample using time-resolved 3D (i.e., four-dimensional or 4D) X-ray imaging. Experiments We performed a capillary-controlled drainage-imbibition experiment on an initially brine-saturated carbonate rock sample. The sample was imaged continuously during imbibition using 4D X-ray imaging to visualize and analyze fluid displacement and snap-off processes at the pore-scale. Findings We discover a new type of snap-off that occurs in pores, resulting in the entrapment of a small portion of the non-wetting phase in pore corners. This contrasts with previously-observed snap-off in throats which traps the non-wetting phase in pore centers. We relate the new type of pore-snap-off to the pinning of fluid-fluid interfaces at rough surfaces, creating contact angles close to 90°. Subsequently, we provide correlations for displacement events as a function of pore-throat geometry. Our findings indicate that having a small throat does not necessarily favor snap-off: the key criterion is the throat radius in relation to the pore radius involved in a displacement event, captured by the aspect ratio.

In this study, the effects of wax deposition on submarine multiphase pipelines are investigated. In order to understand the mechanism of wax deposition in submarine multiphase pipelines, a wax deposition model in a submarine pipeline was established using the OLGA wax deposition module, and key factors influencing this phenomenon were analyzed. Additionally, a multifactor impact analysis of wax deposition was performed via the orthogonal test method. The results indicated the relative influence of five factors on oil-gas-water three-phase wax deposition, namely, oil flow rate, water content, inlet temperature, gas-oil ratio, and outlet pressure. Then, the main influencing factors of wax deposition in a multiphase pipeline flow were extracted, and the wax deposition prediction model was established. The wax deposition rate under different operating conditions was simulated using the OLGA wax deposition simulation module. The SPSS software was used to perform nonlinear regression analysis under different working conditions. In this manner, the constant terms in the wax deposition prediction model for a submarine multiphase pipeline were obtained. The prediction model could be used to programmatically predict wax deposition along a multiphase pipeline by programming the initial waxing conditions. By using this method, the wax deposition prediction model of an M − N submarine multiphase pipeline was obtained under different working conditions. After comparing the predicted and the OLGA simulation results, it was determined that the wax deposition model established could be used to accurately calculate the wax deposition in a submarine multiphase pipeline within an allowable error range. If the physical properties and operating parameters of the conveying medium in a multiphase pipeline are given, the developed oil-gas-water three-phase wax deposition model can be used to predict the distribution of wax deposition in submarine multiphase pipelines without laboratory experiments. The results of this study can help production units understand the waxing situation of pipelines in time in order to scientifically formulate a pigging plan and avoid pipeline blockages and shutdowns.

Hypothesis The stability of fluid–fluid interface is key to control the displacement efficiency in multiphase flow. The existence of particles can alter the interfacial dynamics and induce various morphological patterns. Moreover, the particle aggregations are expected to have a significant impact on the interface stability and patterns. Experiments Monodisperse polyethylene particles of different sizes are uniformly mixed in silicone oil to form the granular mixtures, which are injected into a transparent radial Hele-Shaw cell through different strategies to obtain the homogeneous and inhomogeneous (with particle aggregations) initial states. Subsequently, a systematic study of morphology and interface stability during the withdrawal of granular mixtures is performed. Findings For homogeneous mixtures, we observe earlier onset of fingering, more fingers and lower gas saturation at breakthrough than for pure fluid with equivalent viscosity. This effect can be attributed to the particle-induced perturbations. For inhomogeneous mixtures, particle clusters and bands significantly enhance the interface instability. Furthermore, we find that particle deposition due to liquid film entrainment occurs above a critical local flow velocity, and we elucidate the responsible mechanism through force balance analysis and the thin film theory. This work could be of practical significance in geoenergy and industrial applications.

In this study, defect-free SiOC coatings were prepared on yttria stabilized zirconia (YSZ) microspheres by a fluidized bed coating process. Effects of the rheological properties of the coating solution on the coating process were elucidated. An impact regime diagram was constructed, which demonstrated that the coating mechanisms were collision/impact. During the fluidized bed coating, longer spouted time resulted in wider dispersion, longer residence time, and more circulatory motion of particles; the fluid distributed more uniformly throughout the column, as demonstrated in our Multiphase Flow with Interface eXchange (MFiX) simulations. Two-step pyrolysis in Ar achieved complete coating layers, which were comprised of SiOC, SiO2, SiC, and graphite. The two stage mass loss during the pyrolysis corresponded to simultaneous reactions due to depolymerization and hydrocarbon loss from 400 to 600°C. Carbon cluster size in the pyrolyzed samples was calculated to be 25 ± 2 A. This work provides a new method for producing SiOC coatings on micron spheres, with nuclear TRISO fuel particles as the application.

Hypothesis Interactions between droplets are of fundamental importance for understanding phenomena involving droplet collision and coalescence that determine multiphase flow behavior. The quantitative understanding of these interactions is essential for the manipulation and control of emulsions or complex fluids. The existing methods for interaction force determination are typically based on expensive mechanical probes and fine distance control. Therefore, further development of new techniques for interaction force determination is expected to be beneficial for research on surface force. Experiments In this study, droplet deformation during the interaction between two droplets was captured and analyzed to determine the interaction force. The approach speed of the two droplets was controlled by the injection rate of the fluid. The dynamic interaction force between two tetradecane droplets in various aqueous solutions was determined using the newly developed method, and the effects of two-phase physical properties and operating conditions on the measurement errors were investigated. Findings The droplet profile deformation was first applied as a probe to detect the interaction force. The measurement results were in good agreement with those obtained using the precise weighing sensor of a commercial interfacial tensiometer (K100, Kruss, Germany). The newly developed method was reliable, simple, and did not require the use of expensive devices. Furthermore, droplet deformability was found to be the key parameter in determining the total interaction force between the droplets.

In this paper, a numerical study is performed in order to investigate the effect of the virtual viscosity on simulation of separated two-phase flow of gas-liquid. The governing equations solved by shock capturing method which can provide predicting the interface without the flow field solving. In this work, in order to calculate the numerical flux term, first-order centred scheme (Force scheme) was applied cause of its accuracy and appropriate validation. Analysis approves that the obtained stability range of this research is consistent with the classic Kelvin-Helmholtz instability equation only for the long wavelength with small amplitude. Results reveal that when the wavelengths are reduced, the specified range is not consistent and wavelength affects on instability range and it is over predicted. An algorithm for water faucet problem was developed in Fortran language. Short wavelength perturbations induce unbounded growth rates and make it impossible to achieve converging solutions. The approach taken in this article has been to adding virtual viscosity as a CFD technique, is used to remedy this deficiency.

Subsurface hydrogen (H2) storage in geological formations is of growing interest for decarbonization. However, there is a knowledge gap in understanding the multiphase flow involved in this process, which can have a significant impact on the recovery performance of H2. Therefore, a full-compositional modeling study was conducted to analyze potential issues and to understand the fundamental hydrodynamic mechanisms of H2 storage. We performed a range of 2D vertical simulations at the decametre scale with a very fine cell size (0.1 m) to observe the detailed flow behaviour of H2 with carbon dioxide (CO2) as cushion gas in various flow regimes. Issues such as viscous instability, capillary bypassing, gas trapping and gravity segregation are analysed here. To generalize our calculations, we have validated and applied the scaling theory in the context of subsurface H2 storage. Since this study is focused on the hydrodynamic behaviour, three dimensionless groups, including aspect factor, capillary/viscous ratio and gravity/viscous ratio were identified to correlate recovery performance between various scales in a fixed heterogeneous system. It was found that H2 could infiltrate the cushion gas in the proximity of the injectors, meaning that CO2 is not displaced away from the injectors in a piston-like fashion. As a result, the purity of the back produced H2 is much degraded, particularly in a viscous-dominated scenario. On the other hand, the injected H2 mostly accumulates at the top forming a highly restricted mixing zone with CO2 in the gravity-dominated case. The recovery performance is therefore much improved in this case. Although the gas distribution can be significantly altered by capillary forces leading to bypassed zones, the recovery performance of H2 is hardly influenced. This is because the back-produced H2 recovery is not dependent on the sweep efficiency of the gas. H2 can be back produced following the same paths which were formed during injection.

Fundamental properties of the multicomponent diffuse-interface model (DIM), such as the maximum entropy principle and conservation laws, are used to explore the basic interfacial dynamics and phase transitions in fluids. Flat interfaces with monotonically changing densities of the components are proved to be stable. A liquid layer in contact with oversaturated but stable vapour is shown to either fully evaporate or eternally expand (depending on the initial perturbation), whereas a liquid in contact with saturated vapour always evaporates. If vapour is bounded by a solid wall with a sufficiently large contact angle, spontaneous condensation occurs in the vapour. The external parameters of the multicomponent DIM – e.g. the Korteweg matrix describing the long-range intermolecular forces – are determined for the water/air combination. The Soret and Dufour effects are shown to be negligible in this case, and the interfacial flow, close to isothermal.

Accurate depiction of the process characteristics of dynamic multiphase flows using a data-driven model is a challenge in industrial practices. Collection of sufficient data is costly and cumbersome, and it is difficult to identify representative data efficiently. This article develops an active learning method to explore information from multiphase flow process data, thus facilitating smart process modeling and prediction. An index is proposed to describe the process dynamics and nonlinearity using a probabilistic model, facilitating determination of informative data. The subsequent absorption of these data into the training set enhances the model quality gradually. This is relevant especially for transitional regions exhibiting dynamic information. In addition, a simple and efficient criterion to judge the learning termination has been designed. Consequently, new representative data are explored and learned in a sequential manner. The experimental results of two industrial multiphase flows demonstrate the advantages of the proposed method.

Selected contributions of the 18th Multiphase Flow Conference at HZDR were published Open Access in a special issue Journal Experimental and Computational Multiphase Flow. In this contribution information on the conference is given.

Air-core vortex occurred at the hydraulic intakes deteriorates the performance and operation stability of hydraulic machineries. To investigate the evolution process and generation mechanism of the air-core vortex formed at the vertical intake, large-eddy simulation with the coupled level-set and volume-of-fluid method is performed in a pump sump. This paper elucidates the evolution of velocity distribution caused by pump suction, and associations between vortices motions and velocity evolution and the accompanying free-surface deformations are clarified, which reveals the generation mechanism and evolution characteristics of air-core vortex. Vortices are created by the disturbances of small recirculation zone around the intake pipe. The recirculation is caused by the interaction of the wall of vertical pipe and converging flows with opposite directions driven by the pump suction. The enhancement of vortices due to vortex distortion dominates the air-core vortex formation, and the vertical stretching effect accounts for about 70%. The meandering characteristics of air-core vortex are characterized through analyses of meandering scope and velocity distribution, and the convection of mean flow and sump wall take the leading role in causing its meandering.

This study reports the vibrational turbine piezoelectric nanogenerators (VT-PENG) that use magnetic coupling to trigger a set of silicon rubber strips embedded with piezoelectric films for energy harvesting in amphibious environments. The piezo-rubber strips are deflected by the tip-driven magnets in the strip-anchor systems, such that the VT-PENG can be efficiently triggered to generate electrical energy from mechanical vibration. The VT-PENG prototypes are fabricated, and the experiments are conducted to investigate the energy harvesting performance (i.e., voltage and electrical power) of single and multiple strips of the VT-PENG. Numerical simulations are carried out to validate the experimental results, and satisfactory agreements are observed. The maximum electrical power is obtained as approximately 9 uW for each curved piezoelectric strip and 4 uW for each planar strip. In the end, the field experiments are conducted to test the energy harvesting in the lake. The reported VT-PENG can be applied in low-medium energy harvesting needs under various flow fields.

To reveal the effect of cavitation on the energy conversion characteristics of helical axial multiphase pump (Abbreviated to multiphase pump), the cavitation flow in multiphase pump is simulated. The results show that with the decrease of cavitation number σ, cavitation firstly extends along the streamwise of blade suction side, and then turns to the pressure side of blade. When cavitation develops to fracture stage, the suction side of the blade is completely covered by bubbles; The vapor volume fraction in the impeller is almost 0 at the inception and critical cavitation stages; When cavitation develops to fracture stage, cavitation extends to the whole impeller passage. The output power of impeller is mainly contributed to the power done by the pressure. The power done by the viscous force in the critical fracture cavitation stage is slightly reduced. While, the power done by the pressure in the fracture cavitation stage decreases greatly. With the evolution of cavitation, the turbulence dissipation loss in the impeller decreases gradually. Moreover, in the critical fracture and fracture cavitation stages, the friction loss increases greatly compared with the previous two cavitation stages, resulting in an increment of the total energy loss.

The article highlights the relevance of reliable estimation of the composition and properties of reservoir gas during the development of gas condensate fields and the complexity of the task for reservoirs containing zones of varying condensate content. The authors have developed a methodology that allows monitoring the composition of gas condensate well streams of similar reservoirs. There are successful examples of the approach applied in Achimov gas condensate reservoirs at the Urengoy oil and gas condensate field. The proposed approach is based on the use of the so-called fluid factors, which are calculated on the basis of the known component compositions of various flows of the studied hydrocarbon system. The correlation between certain "fluid factors" and the properties of reservoir gas (usually determined by more labor-consuming methods) allows one to quickly obtain important information necessary to solve various development control tasks.

This paper presents an optimization model based on an oil production system. The objective function is the Net Present Value (NPV) of the profits from hydrocarbon sales, considering the operation costs. The economic objective function is subject to constraints on the reservoir, fluid properties, and multiphase flow in the well. The main variables within the model are the well diameter, reservoir skin factor, rock permeability and gas–oil ratio. This work is presented as an optimization model, because traditionally the production system models are solved by simulation, not ensuring the optimal system solution. Genetic Algorithms are implemented for solving the optimization model because they solve problems with non-convex terms. To obtain the results, the mathematical model was coded in Matlab and was solved with the Genetic Algorithms optimization tool implemented in the software. Four case studies were analyzed. The results indicate that there is an economic improvement in the profits from the sale of hydrocarbon, compared to the solution of the traditional technique by means of Nodal Analysis.

Microbiologically influenced corrosion (MIC) often occurs at the bottom of shale gas-gathering pipelines. Under the condition of pipe flow, the synergistic behavior of SRB corrosion and other factors is not clear. Based on the home-made multiphase flow corrosion loop, the biofilm formation and corrosion of sulfate-reducing bacteria on the surface of a shale gas pipeline steel L360N at different liquid flow rates are studied. At low flow rates such as 0.2 m/s and 0.5 m/s, the SRB biofilm gradually thickens. When the flow rate is 1.0 m/s ~ 1.5 m/s, the existing SRB biofilm is stripped. With the increase in velocity, the average and local corrosion rates first increase and then decrease. The synergistic corrosion of MIC and flow rate in the pipe will change with the increase in flow rate. SRB dominated the corrosion of L360N steel at low flow rate. At high velocity, the corrosion of L360N steel is accelerated by flow erosion after the biofilm is stripped. This study clarifies the corrosion behavior of the interaction between SRB and flow rate, and this understanding has rarely been reported in the past literature and can provide a basis for corrosion protection of shale gas field.

The side-blown vortex smelting reduction reactor proposed in this paper is a new type of metal extraction equipment. The study of fluid dynamics is significant for improving reactor performance. Physical simulation is used to analyze the effects of the angle and number of blown lances, nozzle diameter, gas flow rate, and measuring depths on the reactor’s transfer and mixing characteristics. Dimensional analysis is used to correlate dimensionless numbers (Reynolds number Re, modified Froude number Fr′, capillary number Ca, number of blown lances n, and horizontal angle of the blown lance α) with mixing time and multiphase flow behavior. The results show that when the nozzle diameter and the number of blown lances are constant, Fr′, Ca and α are negatively correlated with the mixing time, and Re is positively correlated with the mixing time. When the angle of the blown lance is constant, Re and Ca are negatively correlated with mixing time, and Fr′ is positively correlated with mixing time. With the increase of Re, Fr′, Ca, the mixing behavior will gradually change from the bubbling regime to the transition regime and then to the steady jetting regime.

This study quantitatively compares the finite element (FE) and lumped modeling techniques to analyze phase-change and multiphase flow in a microchannel evaporator. We compare the one- and two-zone models in the lumped modeling approach by considering both pressure drop and phase change in the evaporator. The study investigates the deviation in results from the lumped model relative to the FE model for various evaporator heat loads. For the one-zone model, the relative errors in predicting the average density, pressure, temperature, and vapor quality increase with the evaporator heat load. This increase is mainly due to the nonlinear variation in the heat transfer coefficient and pressure drop, which are calculated with higher inaccuracies at larger evaporator heat loads. On the other hand, the liquid-phase region and the exit vapor quality are predicted more accurately. The overall errors using one- and two-zone lumped models were less than 30% when the exit qualities do not exceed 0.5. Since strategies involving flow boiling in evaporators typically avoid high exit vapor qualities to circumvent dry-out and critical heat flux, the use of lumped models under these conditions is favorable. This approach also avoids the computational costs associated with FE models while achieving sufficient accuracy to predict the evaporator’s performance.

The investigation of flow field can provide strong theoretical support for improving the flotation performance of fine particles in a cyclonic flotation column. In this study, particle image velocimetry (PIV) is combined with endoscopic measurement and phase discrimination technique to measure the cross section and axial section of gas–liquid two-phase flow field in a lab-scale cyclonic flotation column. The axial, radial, and tangential velocity of both gas and liquid phases are obtained. Based on the PIV experimental data, computational fluid dynamics (CFD)-based numerical models are validated. The results show the good prediction ability of Eulerian–Eulerian multiphase model, Reynolds stress model (RSM), and Tomiyama drag model. Then the simulated results with validated models are displayed to indicate the flow characteristics of the flotation column. The gas concentration is observed to be higher in the center and low on the sides. The gas phase always moves upward, while the liquid phase moves upward at the axis, downward between the axis and the wall, and upward again near the wall. Overall, this study provides an innovative approach for PIV measurement of complex multiphase flow field, and a useful reference for appropriate numerical models selection.

Particle velocity measurement based on cross-correlation algorithm is used widely in various multiphase flow systems. In this study, an optical fiber probe, i.e. Labasys® 100 from MSE Meili was used to systematically compare the qualities of its measured particle velocities in a pair of hydrodynamically distinct regimes, i.e. a fast fluidized bed (FFB) and a bubbling fluidized bed (BFB). Compared to FFBs, the measured particle velocities in BFBs show lower data repeatability, higher percentage of invalid data and higher sensitivity to the selection of the threshold value of maximum cross-correlation coefficient, which corresponds to much lower measurement qualities in this regime. Comparatively, higher measurement qualities were observed in the FFB based on the same evaluating methods. The highest measurement qualities appear in the core region of the riser and under high superficial gas velocities. A matchup relationship between the measurement quality and the shape of the probability density function (PDF) curves of maximum cross-correlation coefficient is found. Narrower PDF curves correspond to higher measurement quality and vice versa.

Due to the low number of experimental investigations on the sizing of safety valves in multiphase flow, a novel set of measurement data of an air-water mixture is reported. This paper presents an experimental study on three different geometries of safety valves, a poppet valve with jet angle θ = 120°, and two-disc valves with deflection angles θ = 0° and θ = 90°, respectively. Our test rig comprises a pipeline with 42.5 mm inner diameter, spray nozzles to supply the added water quality (water mass fraction) to the pressurized airflow up to 40 % mass fraction and an inlet pressure up to 6.6 bar(g). The time histories of force, valve lift, and pressures were recorded. We present correlation data for the force coefficient and the discharge coefficient. The widely used omega technique for the Homogenous Equilibrium Model (HEM) is employed to predict the theoretical mass flux. The results show that the poppet valve experiences less momentum force and lower mass flow rates compared to disc valves, while the disc valve with deflection angle θ = 90° presents the highest discharged flow rates among the tested geometries. Our most important finding is that up to 60 % relative valve lift and 40 % mass fraction, neither the force nor the discharge coefficient changes significantly compared to the pure-air case. Finally, we propose a new correlation with a single equation for the resultant force and the discharge coefficient as a function of the relative valve lift for all tested water mass fractions.

The spatial structure of the constrained space determines the polishing efficiency and polishing quality of the soft abrasive flow (SAF) polishing method. A basic SAF polishing mode with universal guiding significance was built in this paper, and the effect of the spatial structure of constrained space on SAF polishing was studied. Based on the coupling of the Euler’s multiphase flow model and the standard turbulence model, a SAF hydrodynamic model was constructed to obtain the dynamic characteristics of the abrasive flow in the constrained flow passage and to reveal how the key parameters determining the spatial structure of constrained space affect the SAF polishing. The results showed that the inlet angle of the constrained space determines the injection posture of the abrasive flow. When the inlet angle reduces, the impact between the abrasive flow and the constrained wall is weakened, and the distributions of fluid turbulent kinetic energy, dynamic pressure, and granular pressure tend to be uniform. The height of the constrained space is a key factor affecting the polishing efficiency of the SAF. As the height of the space decreases, the material removal rate is enhanced significantly, but the turbulent impact ability of the abrasive particles is weakened. The height of the constrained space should be set to near the critical value of turbulent flow variation. Based upon the simulation, an experimental platform for SAF polishing was built, and the accuracy of the simulation results and the effectiveness of the polishing method were verified by the comparative polishing experiments.

Domain decomposition methods are widely used as preconditioners for Krylov subspace linear solvers. In the simulation of porous media flow there has recently been a growing interest in nonlinear preconditioning methods for Newton’s method. In this work, we perform a numerical study of a spatial additive Schwarz preconditioned exact Newton (ASPEN) method as a nonlinear preconditioner for Newton’s method applied to both fully implicit or sequential implicit schemes for simulating immiscible and compositional multiphase flow. We first review the ASPEN method and discuss how the resulting linearized global equations can be recast so that one can use standard preconditioners developed for the underlying model equations. We observe that the local fully implicit or sequential implicit updates efficiently handle the local nonlinearities, whereas long-range interactions are resolved by the global ASPEN update. The combination of the two updates leads to a very competitive algorithm. We illustrate the behavior of the algorithm for conceptual one and two-dimensional cases, as well as realistic three dimensional models. A complexity analysis demonstrates that Newton’s method with a fully implicit scheme preconditioned by ASPEN is a very robust and scalable alternative to the well-established Newton’s method for fully implicit schemes.

The computational study of transient immiscible and incompressible two-phase flows is one of the most common and desirable way for investigation of engineering phenomena and physics science. In the previous studies, generally bubbles current have been used as an active method for increasing heat transfer, however, due to existence of hydraulic boundary layers, the bubbles were not able to cross over this layer to thinning the thermal boundary layer and consequently the efficiency of this method was not very considerable. In this study, by considering potential of magnetic field, the effect of co-applying of external non uniform magnetic field and magnetic bubbles in enhancing the heat transfer efficiency in a 3-D tube has been investigated. The computational model consisted of the Navier–Stokes equation for liquid phase and VOF model for interface tracking are carried out by OpenFOAM. The external magnetic field has been considered non-uniform and time dependent. The results predicted that magnetic bubbles and external magnetic field due to their effect on thermal boundary layer increased significantly heat transfer and Nusselt number. Furthermore, results indicated magnetic bubbles can act as an active torbulators in the flow field and can be applied for increasing recirculation and secondary flow in the flow field. The average temperature and magnetic field over times for different cases have been discussed in the results.

The asphaltene problem is a two-step process: (1) asphaltene precipitation, as predicted by the thermodynamic model, and (2) asphaltene deposition, the amount of which is estimated by the kinetic model. Asphaltene precipitation is a prerequisite but not a sufficient condition for deposition. Deposition is dependent on other factors such as surface properties, phase behavior, rheology, and flow patterns. As a result, in addition to understanding thermodynamic and kinetic models, it is critical to also understand flow models. In fact, multiphase flow modeling is at the core of simulation, and it must be coupled with thermodynamic and kinetic models. Numerous studies on modeling asphaltene deposition on pipe walls have been performed theoretically and experimentally, but a comprehensive theory to properly understand this phenomenon has not yet been presented. In thermodynamic modeling, the perturbed chain statistical associating fluid theory (PC-SAFT) equation of state is used to predict the asphaltene phase behavior. In this study, we show that the proposed PC-SAFT model is more accurate than the solid model used in commercial software. Unlike prior research that neglected flow patterns or used empirical relations to model multiphase flow, this study simulates multiphase flow using separate momentum equations for each phase. Among the existing kinetic models, the Kurup model has been used to predict the asphaltene deposition profile in the wellbore due to its greater compatibility for computational fluid dynamics application. The results of the proposed model show good agreement with field case data of asphaltene deposition thicknesses along the wellbore tubing.

The internal flow of the mini pumps for washing machines is complex due to its compact structure and it normally adopts the upper drainage method. Due to decline in liquid level at the end of drainage (empty discharge period), the pump experiences water–air multiphase flow condition and produces unsteady flow. This unstable flow not only results in the deterioration of pump energy performance, but also induces larger vibration and noise, which in turn, reduce the working capability of pumps and disturb the people living environment. Therefore, with the aim of exploring the internal flow features and noise characteristics of drainage pumps during empty discharge period, the energy performance test was processed under pure water condition as well as under different air void fraction and part load conditions. Moreover, the internal flow field is calculated based on (both k − e and k − ω) turbulence model and Euler non-uniform stream model under pure water, and different inlet air content for part load conditions, respectively. All the experimental conditions for test and boundary conditions for simulation are provided. The overall and local results of internal flow field and gas phase distribution are obtained and analyzed. In addition, the research results can provide a theoretical recommendation for designing the lower noise mini pumps.

TA15 alloy is susceptible to form bluish-purple thermo-oxidized layer during thermal processing. It is accompanied by surface morphological defects. Laser ablation can remove the thermo-oxidized layer and modify the morphology. However, the pulse width is only a hundred nanoseconds and the spot is in the micron range. It makes the laser-matter interaction investigations extremely challenging. In this paper, a multiphase flow model is established to simulate the removal mechanism of thermo-oxidized layer and surface morphological evolution by nanosecond pulsed laser ablation with different ablation energy densities (E). The critical removal conditions of the thermo-oxidized layer were explored. The critical removal window of the thermo-oxidized layer was determined between 0.1 J/cm2 and 0.35 J/cm2. In conjunction with thermodynamic calculations, the reasons for the minimum surface oxygen content between 3.5 J/cm2 and 8.75 J/cm2 were discussed. A multiphase flow model was used to analyze the formation of crater under time-dependent. Initially, the molten pool is mainly influenced by the recoil pressure and expands outward. Subsequently, the recoil pressure weakens. Instead, convection caused by surface tension and thermal buoyancy forms double vortex. Finally, depending on the low-temperature matrix, the molten pool solidifies rapidly and forms crater.

The current review research's main objective is to develop dispersion models in the multilayer curtain coating with the production of metallized paper. To achieve this, the curtain coating on the paper substrate is employed with respect to multilayer coating of polymers. The first layer of polymer is applied to the paper and then it is subjected to vacuum metallization with aluminum deposition. After it, another second layer of polymer is subjected on it to prevent it from oxidation. These coated polymers are different in nature. The metallized paper will be produced which has high strength will be formulated in this application of curtain coating. The instability of curtain and air entrainment will be minimized from high Weber number, low Reynolds number, Optimum web speed and Coat weights. The above demonstrated process simulation will be modelled in Ansys-CFD. The dispersion of solids in the curtain flow through substrate moving on the web will be evaluated from different numerical methods. Each method has its own characteristics to study the nature of solids dispersion. The high loaded solids dispersion will be investigated from numerical methods including Langrangian Point Particle, Coarse grained molecular dynamics, Stokesian Dynamics, Brownian Dynamics, Point Particle Method Reynolds Averaged Navier Stokes equation, Eulerian Method, Langrangian-Eulerian Point Particle, Large Eddy Simulation point particle, Combined discrete element and Large Eddy Simulation and Discrete Element Methods.

An OpenFOAM application to address black oil problems using the finite volume technique is presented, along with the first results of the new solver. The black oil formulation is well known in petroleum reservoir engineering and widely implemented in primary and secondary recovery processes. Simulation of three-phase flow in porous media including fluid and rock compressibility requires careful consideration in the numerical model in order to guarantee a conservative calculation. Therefore, a detailed mathematical model and its implementation, with emphasis on the numerical treatment, are presented in this work. The solver is validated over several case studies comparing its results against a semi-analytical solution and those obtained by both in-house and commercial simulators reported in the literature, thus proving to successfully represent compressible and incompressible multiphase flow in porous media.

As part of a wider project to understand the applicability of utilising slosh-based damping for wing-like structures, simulations of partially filled tanks subjected to harmonically oscillating and vertical motion are presented. The Volume of Fluid modelling approach is used to capture the air–water interface and different turbulence models based on the Reynolds Averaged Navier– Stokes equations employed. No-model simulations are also conducted to demonstrate the efficacy of using turbulence models in the simulation of sloshing flows. Accuracy of the models is assessed by comparing with recent well-validated experimental data in terms of the damping effect of the sloshing. A wide range of excitation amplitudes are considered in the study to demonstrate the effectiveness of different turbulence models in representing the flow feature of weak and very violent sloshing. The results show that standard turbulence models can produce an excessive dissipation, especially at the interface, leading to inaccuracies in the estimation of sloshing dynamics of the violent sloshing. This issue is absent in the no-model simulations, and better results are obtained for all tested sloshing conditions, suggesting approaches to mitigate this interfacial dissipation within RANS-based modelling is an important consideration for future direction.

Many properties of complex porous media such as reservoir rocks are strongly affected by heterogeneity at different scales. Complex depositional and diagenetic processes have a strong control on the pore structures, leading to systems with a wide range of pore sizes covering many orders of magnitude in length scales. This poses a significant challenge for digital rock analysis since a single resolution image and associated simulation model cannot capture all the relevant length scales in sufficient detail due to limitations in computer memory and speed. The scale-transgressive effects of heterogeneity must therefore be accounted for through a multiscale digital rock workflow. We introduce a generalized multiscale imaging and pore-scale modelling workflow to derive transport properties of complex rocks having broad pore size distributions. A dry/wet micro-CT imaging sequence is used to spatially map the porosity and the connectivity of resolved and unresolved porous regions. The unresolved porosity regions are classified into different porosity classes or rock types. The resulting 3D rock-type map and the porosity map are combined and transformed into a multiscale pore network model. Resolved pores are treated in a conventional pore network manner while unresolved network elements are treated as a continuum Darcy-type porous medium. Similar to conventional continuum models, each Darcy pore is populated with single and multiphase flow properties. These properties are derived from high-resolution rock-type models constructed from backscatter SEM images and/or high-resolution micro-CT images of sub-samples. The multiscale digital rock workflow is applied to two heterogeneous rock samples: a mixed wet thinly laminated reservoir sandstone and an oil wet reservoir carbonate. Experimentally measured mercury–air primary drainage and oil–water imbibition capillary pressure curves (after ageing to restore wettability) are used to anchor the multiscale pore network model. Waterflood relative permeability is calculated in a blind test and compared with high-quality experimental data. A very encouraging agreement between computed and measured properties is found.

A particle-free surface coupled model has been developed using the Eulerian–Eulerian approach for revealing the gas–steel–slag multiphase flow in the vacuum chamber of a 210-ton RH degasser. The particle submodel preferred to predict the gas–steel and gas–slag interpenetrating phenomena, while the free surface submodel focused on tracking the steel–slag interface flow. The mesh sensitivity analysis has been investigated, and the coupled model was validated by the measured values. Using this coupled model, some previously unknown problems about multiphase flow in the vacuum chamber were revealed, such as the effect of the free surface fluctuation, variation of the liquid level, and slag flow behavior.

Numerical methods that are mass conservative, computationally stable, and efficient are essential for simulating multiphase flow in fractured porous reservoirs. In this paper, a fully mass conservative numerical method that meets these requirements is proposed and analyzed. Unlike in the implicit pressure and explicit saturation (IMPES) method, in this method, the pressure and saturation equations are solved sequentially in each iteration step. In this framework, the calculation of the saturation-related parameters no longer depends on the initial conditions of the current time step, but on the results of the current and previous iterations. Through this treatment, the discontinuities of the saturation and capillary pressure in the pre- and post-two time steps can be overcome to achieve fully mass conservation. Two numerical examples are designed to verify the robustness and efficiency of the presented method. The numerical results indicate that this new method is fully mass conservative, computationally more stable, and more efficient than the IMPES method. Furthermore, the proposed method is suitable not only for reservoirs with homogeneous permeability distributions but also for reservoirs with heterogeneous permeability distributions, which greatly improves the applicability of the new method.

PurposeThe purpose of this paper is to study the multi-phase flow behaviors in solid fluidization exploitation of natural gas hydrate (NGH) and its effect on the engineering safety.Design/methodology/approachIn this paper, a multi-phase flow model considering the endothermic decomposition of hydrate is established and finite difference method is used to solve the mathematical model. The model is validated by reproducing the field test data of a well in Shenhu Sea area. Besides, optimization of design parameters is presented to ensure engineering safety during the solid fluidization exploitation of NGH in South China Sea.FindingsTo ensure the engineering safety during solid fluidization exploitation of marine NGH, taking the test well as an example, a drilling flow rate range of 40–50 L/s, drilling fluid density range of 1.2–1.23 g/cm3 and rate of penetration (ROP) range of 10–20 m/h should be recommended. Besides, pre-cooled drilling fluid is also helpful for inhibiting hydrate decomposition.Originality/valueSystematic research on the effect of multiphase flow behaviors on the engineering safety is scare, especially for the solid fluidization exploitation of NGH in South China Sea. With the growing demand for energy, it is of great significance to ensure the engineering safety before the large-scale extraction of commercial gas from hydrate deposits. The result of this study can provide profound theoretical bases and valuable technical guidance for the commercial solid fluidization exploitation of NGH in South China Sea.