Processes

Research

18 pages, 8969 KiB

Open AccessArticle

Study on the Behavior and State of Viscous Fractured Leakage Bridging and Plugging Slurry during the Pump-In and Pressurization Process

by Yanhui Wu, Cheng Han, Yi Huang, Wandong Zhang, Ming Luo, Peng Xu and Qinglin Liu

Processes 2024, 12(1), 203; https://doi.org/10.3390/pr12010203 - 17 Jan 2024

Viewed by 842

Abstract

Clarifying the process of bridging and plugging slurry during pumping and squeezing can effectively improve the efficiency and accuracy of fractured leakage treatment while minimizing impacts on safety and the environment. In this paper, computational fluid dynamics (CFD) numerical simulation and experimentation (hydrostatic [...] Read more.

Clarifying the process of bridging and plugging slurry during pumping and squeezing can effectively improve the efficiency and accuracy of fractured leakage treatment while minimizing impacts on safety and the environment. In this paper, computational fluid dynamics (CFD) numerical simulation and experimentation (hydrostatic settling method) are combined to evaluate the dynamic settlement process of different types of plugging slurry through sedimentation changes, sedimentation volume, sedimentation velocity and sedimentation height for factors such as viscosity, particle size, density and concentration of plugging slurry. The formula of particle sedimentation velocity is combined to obtain the following: When the viscosity of plugging slurry is more than 30 mPa·s, the particle diameter is 1.5 mm (particle size is half the fracture width), and the particle density is 2.0–2.6 g/cm³; it shows good dispersion and plugging performance under pumping pressure and while holding and squeezing after lifting the bit. The simulation results show that the particle density should not exceed two times the plugging slurry density, and the particle concentration has little influence on the particle settling volume. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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15 pages, 12714 KiB

Open AccessArticle

Numerical Analysis of Viscous Polymer Resin Mixing Processes in High-Speed Blade-Free Planetary Blender Using Smoothed Particle Hydrodynamics

by Kwon Joong Son

Processes 2023, 11(9), 2555; https://doi.org/10.3390/pr11092555 - 25 Aug 2023

Cited by 1 | Viewed by 1368

Abstract

High-speed planetary mixers can rapidly and efficiently combine rheological liquids, such as polymer resins and paste materials, because of the large centrifugal forces generated by the planetary motion of the mixing vessel. Only a few attempts have been made to computationally model and [...] Read more.

High-speed planetary mixers can rapidly and efficiently combine rheological liquids, such as polymer resins and paste materials, because of the large centrifugal forces generated by the planetary motion of the mixing vessel. Only a few attempts have been made to computationally model and analyze the intricate mixing patterns of highly viscous substances. This paper presents meshless flow simulations of the planetary mixing of polymeric fluids. This research utilized the smoothed particle hydrodynamics (SPH) approach for numerical calculations. This method has advantages over the finite-volume method, which is a grid-based computational technique, when it comes to modeling interfacial and free surface flow problems. Newtonian rheology and interfacial surface force models were used to calculate the dissipative forces in the partial differential momentum equation of fluid motion. Simulations of the flow of an uncured polyurethane resin were carried out while it was mixed in a planetary mixer, under various operating conditions. Simulations using SPH were able to accurately reproduce the intricate flow and blending pattern, providing insight into mixing mechanics and mixing index evolution characteristics according to operating conditions for the planetary mixing of polymeric fluids. The simulation results showed that the spiral band, which promotes the mixing performance, is densely and distinctively formed under high-speed operation conditions. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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16 pages, 4667 KiB

Open AccessArticle

Pneumatic Noise Study of Multi-Stage Sleeve Control Valve

by Jianbo Jia, Yan Shi, Xianyu Meng, Bo Zhang and Dameng Li

Processes 2023, 11(9), 2544; https://doi.org/10.3390/pr11092544 - 25 Aug 2023

Viewed by 2097

Abstract

This study considers the practical issue of severe noise observed in a multi-stage sleeve control valve within an engineering project. Employing computational fluid dynamics (CFD) methodology, we initially performed numerical simulations to analyze the steady-state flow field within the control valve. Subsequently, we [...] Read more.

This study considers the practical issue of severe noise observed in a multi-stage sleeve control valve within an engineering project. Employing computational fluid dynamics (CFD) methodology, we initially performed numerical simulations to analyze the steady-state flow field within the control valve. Subsequently, we identified the underlying factors contributing to the noise issue within the valve. To assess the aerodynamic noise of the control valve, we applied the FW-H acoustic analogy theory and determined the intensity and distribution characteristics of the aerodynamic noise. Finally, we validated the numerical simulation results of the aerodynamic noise against theoretical calculations. Our findings indicate that the steam medium experiences high-speed flow due to disturbances caused by various components within the valve, resulting in significant turbulence intensity. This intense turbulence leads to pressure fluctuations in the steam, serving as the main catalyst for noise generation. The aerodynamic noise of the control valve exhibits a roughly symmetrical distribution along the pipe–valve system, with noticeable increases in noise levels upstream and downstream of the valve compared to other regions. The distribution cloud map obtained from the numerical simulations serves as a valuable reference for analyzing the locations where aerodynamic noise is generated. Comparing the numerical simulation results with the theoretical calculations at the noise monitoring points, we found that the noise error of the monitoring points was less than 5%, which proves the effectiveness of the numerical simulation method. These results provide essential data support for the acoustic detection of aerodynamic noise in control valves, carrying significant practical implications for engineering applications. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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17 pages, 3956 KiB

Open AccessFeature PaperArticle

Numerical Study on High Throughput and High Solid Particle Separation in Deterministic Lateral Displacement Microarrays

by Maike S. Wullenweber, Jonathan Kottmeier, Ingo Kampen, Andreas Dietzel and Arno Kwade

Processes 2023, 11(8), 2438; https://doi.org/10.3390/pr11082438 - 13 Aug 2023

Cited by 2 | Viewed by 1513

Abstract

Deterministic lateral displacement (DLD) is a high-resolution passive microfluidic separation method for separating micron-scale particles according to their size. Optimizing these microsystems for larger throughputs and particle concentrations is of interest for industrial applications. This study evaluates the limitations of the functionality of [...] Read more.

Deterministic lateral displacement (DLD) is a high-resolution passive microfluidic separation method for separating micron-scale particles according to their size. Optimizing these microsystems for larger throughputs and particle concentrations is of interest for industrial applications. This study evaluates the limitations of the functionality of the DLD separation principle under these specific conditions. For this reason, different particle volume fractions (up to 11%) and volumetric flow rates (corresponding to Reynolds numbers up to 50) were varied within the DLD microsystem and tested in different combinations. Resolved two-way coupled computational fluid dynamics/discrete element method (CFD-DEM) simulations including spherical particles were performed. The results show a general increase in the critical diameter with increasing volume fraction and decreasing separation efficiency. The largest tested Reynolds number (Re = 50) results in the highest separation efficiency, particularly at low volume fractions, and is only slightly less efficient than low Reynolds numbers as the volume fraction increases. The results indicate that by limiting the volume fraction to a maximum of 3.6%, the flow rate and the associated separation rate can be increased while maintaining a high separation efficiency. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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15 pages, 6578 KiB

Open AccessArticle

Direct Numerical Simulation of Bubble Cluster Collapse: Shape Evolution and Energy Transfer Mechanisms

by Jiacheng Ye, Jing Zhang and Tianyang Huang

Processes 2023, 11(7), 2191; https://doi.org/10.3390/pr11072191 - 21 Jul 2023

Cited by 2 | Viewed by 1310

Abstract

This study employs the VOF method to conduct the direct numerical simulation of the collapse progress of the near-wall bubble cluster. Factors such as viscosity, compressibility, and surface tension are taken into account, with an emphasis on the flow field energy evolution. Firstly, [...] Read more.

This study employs the VOF method to conduct the direct numerical simulation of the collapse progress of the near-wall bubble cluster. Factors such as viscosity, compressibility, and surface tension are taken into account, with an emphasis on the flow field energy evolution. Firstly, the collapse of a cubic bubble cluster comprising 64 bubbles is simulated, validating previous research regarding the morphological evolution and energy release mechanisms during cluster collapse. Overall, the cubic bubble cluster collapse exhibits a layer-by-layer phenomenon, where the outer layer bubbles collapse first, converting a portion of bubble potential energy into fluid kinetic energy, which then contributes to the inner layer bubble collapse. The pressure wave energy is primarily released when the whole bubble cluster completely collapses. Secondly, we investigate the collapse process of columnar bubble clusters, which closely resemble realistic cloud cavitation. By comparing the collapse behavior of bubble clusters with different heights, we reveal the non-linear delay effect of the cluster height on the collapse time. Additionally, we consolidate our long-term research on the bubble cluster and conclude that both the scale and shape of the bubble clusters have a limited impact on the conversion rate

η

of bubble potential energy to pressure wave energy

η

. For instance, when the stand-off distance

η = 1.5

and the inter-bubble distance

D = 2.5

, the conversion rate

η

remains consistently 9–15% for various bubble clusters of different scales and shapes. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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30 pages, 12839 KiB

Open AccessArticle

Nonlinear Analysis of Cross Rolls of Electrically Conducting Fluid under an Applied Magnetic Field with Rotation

by Y. Rameshwar, G. Srinivas, A. Krishna Rao, U. S. Mahabaleshwar and D. Laroze

Processes 2023, 11(7), 1945; https://doi.org/10.3390/pr11071945 - 27 Jun 2023

Cited by 1 | Viewed by 865

Abstract

The proposed planer layer dynamo physical model has real-world applications, especially in the Earth’s liquid core. Thus, in this paper, an attempt is made to understand the finite amplitude convection when there exists a coupling between the Lorentz force and the Coriolis force. [...] Read more.

The proposed planer layer dynamo physical model has real-world applications, especially in the Earth’s liquid core. Thus, in this paper, an attempt is made to understand the finite amplitude convection when there exists a coupling between the Lorentz force and the Coriolis force. In particular, the effect of a horizontally applied magnetic field is studied on the Rayleigh–Bénard convection (RBC) that contains the electrically conducting fluid and rotates about its vertical axis. Free–free boundary conditions are assumed on the geometry. Attention is focused on the nonlinear convective flow behavior during the occurrence of cross rolls which are perpendicular to the applied magnetic field and parallel to the rotation axis. The visualization of cross rolls is achieved using the Fourier analysis of perturbations up to the O(

ε^{8}

). The relationship of the Nusselt number (

N u

) with respect to the Rayleigh number (R), the Ekman number (E), and the Elsasser number (

Λ

) is investigated. It is observed that E generates a strong damping effect on the flow velocity and on the heat transfer at high rotation rates. Using the heatline concept, it is observed that the temperature within the central regime is enhanced as the

Λ

increases. The results show that either E decreases or

Λ

increases, then the heat transfer rate increases. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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13 pages, 956 KiB

Open AccessEditor’s ChoiceArticle

Droplet Based Estimation of Viscosity of Water–PVP Solutions Using Convolutional Neural Networks

by Mohamed Azouz Mrad, Kristof Csorba, Dorián László Galata, Zsombor Kristóf Nagy and Hassan Charaf

Processes 2023, 11(7), 1917; https://doi.org/10.3390/pr11071917 - 26 Jun 2023

Viewed by 1442

Abstract

The viscosity of a liquid is the property that measures the liquid’s internal resistance to flow. Monitoring viscosity is a vital component of quality control in several industrial fields, including chemical, pharmaceutical, food, and energy-related industries. In many industries, the most commonly used [...] Read more.

The viscosity of a liquid is the property that measures the liquid’s internal resistance to flow. Monitoring viscosity is a vital component of quality control in several industrial fields, including chemical, pharmaceutical, food, and energy-related industries. In many industries, the most commonly used instrument for measuring viscosity is capillary viscometers, but their cost and complexity pose challenges for these industries where accurate and real-time viscosity information is vital. In this work, we prepared fourteen solutions with different water and PVP (Polyvinylpyrrolidone) ratios, measured their different viscosity values, and produced videos of their droplets. We extracted the images of the fully developed droplets from the videos and we used the images to train a convolutional neural network model to estimate the viscosity values of the water–PVP solutions. The proposed model was able to accurately estimate the viscosity values of samples of unseen chemical formulations with the same composition with a low MSE score of 0.0243 and R2 score of 0.9576. The proposed method has potential applications in scenarios where real-time monitoring of liquid viscosity is required. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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20 pages, 6125 KiB

Open AccessArticle

Numerical Analysis of the Blockage Effect of the Tunnel Drainage System on the E-Han Expressway

by Yun Li, Shiyang Liu, Shaojie Guan, Feng Gao and Yian Zhang

Processes 2023, 11(3), 949; https://doi.org/10.3390/pr11030949 - 20 Mar 2023

Viewed by 1620

Abstract

The discharge of groundwater and the load on the lining structure are both significantly impacted by the obstruction of the tunnel drainage system. In this study, the fluid–structure interaction model was established based on the finite difference software FLAC^3D. Then, this [...] Read more.

The discharge of groundwater and the load on the lining structure are both significantly impacted by the obstruction of the tunnel drainage system. In this study, the fluid–structure interaction model was established based on the finite difference software FLAC^3D. Then, this research explored the effects of symmetric and asymmetric blockage in the circular drainpipe, the transverse drainpipe and at the pipe joint in the tunnel on the pore water pressure, displacement and stress of surrounding rock. Our research revealed the following points: (1) When a symmetrical or asymmetrical blockage occurred in a circular drainpipe, only the blocked part of the drainpipe would be affected, but the pore water pressure at the back side of the tunnel crown and side wall lining between two adjacent circular drainpipes would increase by 200%, stress increase would increase by 22% and displacement would increase by 41%. (2) When a symmetrical or asymmetrical blockage occurred in a transverse drainpipe, the pore water pressure at the back side of the tunnel crown and side wall lining between two adjacent circular drainpipes increased by a maximum of 146%, the stress on the tunnel crown lining increased by a maximum of 4% and the tunnel crown lining was displaced by 8% to a maximum extent. (3) Both symmetrical and asymmetrical blockage of the tunnel drain joint led to the failures of the circular drainpipe and the transverse drainpipe connected with the tunnel drain joint. This increased the pore water pressure on the back side of the lining between the two adjacent drain sections and had an impact on the pore water pressure, stress and displacement of the surrounding rock nearby. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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14 pages, 2177 KiB

Open AccessArticle

Numerical Investigation of the Use of Boron Nitride/Water and Conventional Nanofluids in a Microchannel Heat Sink

by Fuat Kaya

Processes 2022, 10(12), 2639; https://doi.org/10.3390/pr10122639 - 8 Dec 2022

Viewed by 1306

Abstract

The purpose of this paper is to study the effects of the use of boron nitride (BN) and other conventional nanoparticles (Al₂O₃, CuO and TiO₂) on pressure drop and heat transfer in a microchannel. The governing equations [...] Read more.

The purpose of this paper is to study the effects of the use of boron nitride (BN) and other conventional nanoparticles (Al₂O₃, CuO and TiO₂) on pressure drop and heat transfer in a microchannel. The governing equations for forced fluid flow and heat transfer were worked out by using fluent computational fluid dynamics (CFD) code. Computational results collected from fluent CFD code for Al₂O₃ as the nano-particle were compared with numerical values used in the literature for validation. The basis of a water-cooled (pure water, Al₂O₃/Water, CuO/Water, TiO₂/Water and BN/Water) smooth microchannel was outlined, and then the corresponding laminar flow and heat transfer were evaluated numerically. The results from the numerical tests (NT) express good agreement with the values found in the literature. These results also indicate, through the comparison which was performed by taking the heat transfer and pressure loss parameters between BN and other widely used conventional nanoparticles (Al₂O₃, CuO and TiO₂) into consideration, that BN is the more favorable nanoparticle. In comparison to other common nanoparticles (Al₂O₃, CuO and TiO₂), BN enhances heat transfer and slightly raised pressure losses owing to its high thermal conductivity and high velocity profile because of low density. It is also chemically stable at the highest temperature relative to most solid materials. Thus, it has a structure that can be used in cooling systems for a long time without causing a problem of agglomeration. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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11 pages, 2603 KiB

Open AccessEditor’s ChoiceCommunication

Application of the Analogy between Momentum and Heat Flux in Turbulent Flow of a Straight Tube to a Spiral Tube

by Kye-Bock Lee, Eui-Hyeok Song, Ji-Su Lee and Seok-Ho Rhi

Processes 2022, 10(10), 1927; https://doi.org/10.3390/pr10101927 - 23 Sep 2022

Cited by 1 | Viewed by 2358

Abstract

A theory-based prediction method was used to estimate the friction factor and heat transfer rate in the turbulent flow of a helically coiled tube. The secondary flow produced by a centrifugal force improves heat and mass transfer; therefore, spiral coil pipes are widely [...] Read more.

A theory-based prediction method was used to estimate the friction factor and heat transfer rate in the turbulent flow of a helically coiled tube. The secondary flow produced by a centrifugal force improves heat and mass transfer; therefore, spiral coil pipes are widely used in a variety of industrial applications. The law of the wall and the Reynolds analogy, which states that momentum transfer in a turbulent flow is equivalent to heat transfer, were used in this theoretical method. The logarithmic law was used to characterize the velocity profile in the turbulence-dominated region, and the local wall shear stress variation throughout the circumference of the helical tube wall was considered. The friction factor and heat transfer in the turbulent flow of the helically coiled tube were accurately predicted by the model. Using the Reynolds analogy, the local Nusselt number in the circumferential direction of the helical tube wall was determined. The effect of decreasing local heat transfer within the tube while increasing heat transfer outside the tube was quantified. The analogy between the momentum flux and the heat flux in the turbulent flow of the straight tube was also proven to be applicable to the spiral tube. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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22 pages, 4894 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A CFD Investigation on the Aerosol Drug Delivery in the Mouth–Throat Airway Using a Pressurized Metered-Dose Inhaler Device

by Farnia Dastoorian, Leila Pakzad, Janusz Kozinski and Ehsan Behzadfar

Processes 2022, 10(7), 1230; https://doi.org/10.3390/pr10071230 - 21 Jun 2022

Cited by 9 | Viewed by 3099

Abstract

Inhalation therapy involving a pressurized metered-dose inhaler (pMDI) is one of the most commonly used and effective treatment methods for patients with asthma. The purpose of this study was to develop a computational fluid dynamics (CFD) model to characterize aerosol flow issued from [...] Read more.

Inhalation therapy involving a pressurized metered-dose inhaler (pMDI) is one of the most commonly used and effective treatment methods for patients with asthma. The purpose of this study was to develop a computational fluid dynamics (CFD) model to characterize aerosol flow issued from a pMDI into a simulated mouth–throat geometry. The effects of air flow rate and cone angle were analyzed in detail. The behaviour of the multiphase flow initiated at the inhaler actuation nozzle and extended through the mouth–throat airway was simulated based on the Eulerian-Lagrangian discrete phase model, with the k-ω model applied for turbulency. We validated our model against published experimental measurements and cover the hydrodynamic aspect of the study. The recirculation we observed at the 90° bend inside the mouth–throat airway resulted in the selective retention of larger diameter particles, and the fluid flow patterns were correlated with drug deposition behaviour. Enhancing air flow rates up to three times reduced the aerodynamic particle diameters to 20%. We also observed that, as cone angle increased, mouth deposition increased; an 8° cone angle was the best angle for the lowest mouth–throat deposition. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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17 pages, 5543 KiB

Open AccessArticle

Hydrodynamics of an Elliptical Squirmer

by Chen Liu, Peijie Zhang, Jianzhong Lin and Zhenyu Ouyang

Processes 2022, 10(5), 805; https://doi.org/10.3390/pr10050805 - 19 Apr 2022

Cited by 5 | Viewed by 2359

Abstract

In this paper the propulsion of elliptical objects (called squirmers) by imposed tangential velocity along the surface is studied. For a symmetric velocity distribution (a neutral squirmer), pushers (increased tangential velocity on the downstream side of the ellipse) and pullers (increased tangential velocity [...] Read more.

In this paper the propulsion of elliptical objects (called squirmers) by imposed tangential velocity along the surface is studied. For a symmetric velocity distribution (a neutral squirmer), pushers (increased tangential velocity on the downstream side of the ellipse) and pullers (increased tangential velocity on the upstream side of the ellipse), the hydrodynamic characteristics, are simulated numerically using the immersed boundary-lattice Boltzmann method. The accuracy of the numerical scheme and code are validated. The effects of Reynolds number (Re) and squirmer aspect ratio (AR) on the velocity u*, power expenditure P* and hydrodynamic efficiency η of the squirmer are explored. The results show that the change of u* along radial direction r* shows the relation of u*~r*⁻² for the neutral squirmer, and u*~r*⁻¹ for the pusher and puller. With the increase of Re, u* of the pusher increases monotonically, but u* of the puller decreases from Re = 0.01 to 0.3, and then increases from Re = 0.3 to 3. The values of P* of the pusher and puller are the same for 0.01 ≤ Re ≤ 0.3; P* of the pusher is larger than that of the puller when Re > 0.3. η of the pusher and puller increases with increasing Re, but the pusher has a larger η than the puller at the same Re. u* and P* decrease with increasing AR, and the pusher and puller have the largest and least u*, respectively. The values of P* of the pusher and puller are almost the same and are much larger than those of the neutral squirmer. With the increase of AR, η increases for the neutral squirmer, but changes non-monotonically for the pusher and puller. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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15 pages, 5263 KiB

Open AccessArticle

Sensitivity Test of Jet Velocity and Void Fraction on the Prediction of Rise Height and Performance of a Confined Plunging Liquid Jet Reactor

by Bader S. Al-Anzi and Jenifer Fernandes

Processes 2022, 10(1), 160; https://doi.org/10.3390/pr10010160 - 13 Jan 2022

Cited by 6 | Viewed by 2194

Abstract

Jet velocity is an important parameter affecting the air entrainment rate of plunging liquid jet processes. While the vast majority of researchers have investigated the effect of jet velocity, only a few of them considered the effect of jet length in calculating the [...] Read more.

Jet velocity is an important parameter affecting the air entrainment rate of plunging liquid jet processes. While the vast majority of researchers have investigated the effect of jet velocity, only a few of them considered the effect of jet length in calculating the jet velocity at impingement point. This study investigates the difference (ΔV) between the jet velocity at the inception of the nozzle (V_j) and the impingement point (V_L) for a range of operating conditions. Furthermore, bubble voidage inside the downcomer, another critical parameter in plunging jets, is estimated using three different voidage equations incorporated inside a momentum balance model to predict the two-phase elevation level (H_R) inside the downcomer. Results showed that ΔV is significant (V_L > V_j), especially at low jet flow rates and high jet lengths. Generally, the momentum balance model predicted the H_R well, and its prediction improves with downcomer diameter. Given that, the model still needs to be refined for more accuracy for a wide range of operating conditions. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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21 pages, 11450 KiB

Open AccessArticle

Effect of Different Configurations on Bubble Cutting and Process Intensification in a Micro-Structured Jet Bubble Column Using Digital Image Analysis

by Guanghui Chen, Zhongcheng Zhang, Fei Gao, Jianlong Li and Jipeng Dong

Processes 2021, 9(12), 2220; https://doi.org/10.3390/pr9122220 - 9 Dec 2021

Cited by 4 | Viewed by 2627

Abstract

An experimental study was conducted in this work to investigate the effect of different configurations on bubble cutting and process intensification in a micro-structured jet bubble column (MSJBC). Hydrodynamic parameters, including bubble size, flow field, liquid velocity, gas holdup as well as the [...] Read more.

An experimental study was conducted in this work to investigate the effect of different configurations on bubble cutting and process intensification in a micro-structured jet bubble column (MSJBC). Hydrodynamic parameters, including bubble size, flow field, liquid velocity, gas holdup as well as the interfacial area, were compared and researched for a MSJBC with and without mesh. The bubble dynamics and cutting images were recorded by a non-invasive optical measurement. An advanced particle image velocimetry technique (digital image analysis) was used to investigate the influence of different configurations on the surrounding flow field and liquid velocity. When there was a single mesh and two stages of mesh compared with no mesh, the experimental results showed that the bubble size decreased by 22.7% and 29.7%, the gas holdup increased by 5.7% and 9.7%, and the interfacial area increased by more than 34.8% and 43.5%, respectively. Significant changes in the flow field distribution caused by the intrusive effect of the mesh were observed, resulting in separate liquid circulation patterns near the wire mesh, which could alleviate the liquid back-mixing. The mass transfer experiment results on the chemical absorption of CO₂ into NaOH enhanced by a mass transfer process show that the reaction time to equilibrium is greatly reduced in the presence of the mesh in the column. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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13 pages, 2088 KiB

Open AccessArticle

Modeling Transient Flow in CO₂ Injection Wells by Considering the Phase Change

by Nian-Hui Wan, Li-Song Wang, Lin-Tong Hou, Qi-Lin Wu and Jing-Yu Xu

Processes 2021, 9(12), 2164; https://doi.org/10.3390/pr9122164 - 1 Dec 2021

Cited by 6 | Viewed by 3173

Abstract

A transient model to simulate the temperature and pressure in CO₂ injection wells is proposed and solved using the finite difference method. The model couples the variability of CO₂ properties and conservation laws. The maximum error between the simulated and measured [...] Read more.

A transient model to simulate the temperature and pressure in CO₂ injection wells is proposed and solved using the finite difference method. The model couples the variability of CO₂ properties and conservation laws. The maximum error between the simulated and measured results is 5.04%. The case study shows that the phase state is primarily controlled by the wellbore temperature. Increasing the injection temperature or decreasing the injection rate contributes to obtaining the supercritical state. The variability of density can be ignored when the injection rate is low, but for a high injection rate, ignoring this may cause considerable errors in pressure profiles. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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19 pages, 7522 KiB

Open AccessArticle

Comparative Study on the Power Consumption and Flow Field Characteristics of a Three-Blade Combined Agitator

by Yan Zhang, Lixin Zhang, Huan Wang, Xiao Ma, Siyao Yu, Yongchun Yan and Haoran Bu

Processes 2021, 9(11), 1962; https://doi.org/10.3390/pr9111962 - 2 Nov 2021

Cited by 3 | Viewed by 3573

Abstract

The three-blade combined agitator consists of two propulsion blades of the same type (including planar propeller blades b, δ = 36.87°) and a curved blade (θ = 30°). Using numerical simulation methods, the power characteristics, flow field distribution, turbulence characteristics and [...] Read more.

The three-blade combined agitator consists of two propulsion blades of the same type (including planar propeller blades b, δ = 36.87°) and a curved blade (θ = 30°). Using numerical simulation methods, the power characteristics, flow field distribution, turbulence characteristics and dead zone percentage of two kinds of three-blade combined agitators (TBCAs) from laminar flow to turbulent flow in a mixing vessel were studied. Moreover, the torque measurement method was used to perform experimental verification. The results show that the predicted power curve is consistent with the experimental results. The fluid velocity near the propeller blades in the TBC-B type agitator (δ = 36.87°) is significantly high, and the maximum increase of the total velocity can reach 30.3%. The fluid flow velocity near the curved blades is increased, and the radial diffusion ability of the fluid at the bottom of the stirring vessel is enhanced. When mixing low-viscosity fluids, the TBC-B type agitator can increase the fluid velocity near the paddle area, with a maximum increase of 22.1%. The vertical combination of curved blades and planar propeller blades can effectively reduce the tangential velocity and increase the axial and radial velocities. When stirring high-viscosity fluids, the speed of the TBC-B type agitator in the near paddle area and far end of the blade is higher than that of the TBC-A type agitator. Under the same conditions, the TBC-B-type agitator exhibits superior fluid discharge performance and can be used in a wider range of viscosities. When Re = 44,910, the dead zone percentage of the TBC-A type agitator is 0.0216. The percentage of dead zones produced by the TBC-B-type agitator is smaller, and the mixing effect is superior to that of the TBC-A-type agitator. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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18 pages, 6604 KiB

Open AccessArticle

A Suitable Shape of the Suction Head for a Cleaning Process in a Factory Developed by Computational Fluid Dynamics

by Jatuporn Thongsri, Worapol Tangsopa and Jirawat Khongsin

Processes 2021, 9(11), 1902; https://doi.org/10.3390/pr9111902 - 25 Oct 2021

Cited by 4 | Viewed by 2678

Abstract

The previous shape of the suction head (SH) employed in a cleaning process in a factory had a low performance, removed fewer particles, and generated an annoying noise. Therefore, new shapes of SH have been proposed to solve the issues and the cleaning [...] Read more.

The previous shape of the suction head (SH) employed in a cleaning process in a factory had a low performance, removed fewer particles, and generated an annoying noise. Therefore, new shapes of SH have been proposed to solve the issues and the cleaning performance was investigated by the Shear Stress Transport (SST) k-ω turbulence, Discrete Phase (DP), Large Eddy Simulation (LES), and Ffowcs Williams and Hawkings (FW–H) models in a transient state of computational fluid dynamics (CFD). The SST k-ω and DP models were applied to determine the airflow, suspension velocity, cleaning region, and particle trace. In addition, the LES and FW–H models were used to evaluate the noise, sound pressure level, and frequency generated from the proposed shapes. All simulation results were validated with the air velocity and noise measurements and were analyzed to find a suitable shape. The simulation and experimental results revealed that the shapes of the SH affected the cleaning performance and noise generation. The higher the air velocity, the higher the noise generation. The suitable shape delivered a 4.37% better particle removing performance and 11.1 dB less noise generation than the previous shape. The outcomes of this research are the suitable shape of the SH and the research methodology which enabled the application of both CFD and experiments to solve the issue to help enhance the efficiency of the cleaning process in an actual factory. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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22 pages, 6181 KiB

Open AccessArticle

Analyzing Impacts of Interfacial Instabilities on the Sweeping Power of Newtonian Fluids to Immiscibly Displace Power-Law Materials

by Morteza Esmaeilpour and Maziar Gholami Korzani

Processes 2021, 9(5), 742; https://doi.org/10.3390/pr9050742 - 22 Apr 2021

Cited by 3 | Viewed by 3294

Abstract

Injection of Newtonian fluids to displace pseudoplastic and dilatant fluids, governed by the power-law viscosity relationship, is common in many industrial processes. In these applications, changing the viscosity of the displaced fluid through velocity alteration can regulate interfacial instabilities, displacement efficiency, the thickness [...] Read more.

Injection of Newtonian fluids to displace pseudoplastic and dilatant fluids, governed by the power-law viscosity relationship, is common in many industrial processes. In these applications, changing the viscosity of the displaced fluid through velocity alteration can regulate interfacial instabilities, displacement efficiency, the thickness of the static wall layer, and the injected fluid’s tendency to move toward particular parts of the channel. The dynamic behavior of the fluid–fluid interface in the case of immiscibility is highly complicated and complex. In this study, a code was developed that utilizes a multi-component model of the lattice Boltzmann method to decrease the computational cost and accurately model these problems. Accordingly, a 2D inclined channel, filled with a stagnant incompressible Newtonian fluid in the initial section followed by a power-law material, was modeled for numerous scenarios. In conclusion, the results indicate that reducing the power-law index can regulate interfacial instabilities leading to dynamic deformation of static wall layers at the top and the bottom of the channel. However, it does not guarantee a reduction in the thickness of these layers, which is crucial to improve displacement efficiency. The impacts of the compatibility factor and power-law index variations on the filling pattern and finger structure were intensively evaluated. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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26 pages, 10513 KiB

Open AccessArticle

3D Multidisciplinary Automated Design Optimization Toolbox for Wind Turbine Blades

by Sagi Sagimbayev, Yestay Kylyshbek, Sagidolla Batay, Yong Zhao, Sai Fok and Teh Soo Lee

Processes 2021, 9(4), 581; https://doi.org/10.3390/pr9040581 - 26 Mar 2021

Cited by 10 | Viewed by 2838

Abstract

This paper presents two novel automated optimization approaches. The first one proposes a framework to optimize wind turbine blades by integrating multidisciplinary 3D parametric modeling, a physics-based optimization scheme, the Inverse Blade Element Momentum (IBEM) method, and 3D Reynolds-averaged Navier–Stokes (RANS) simulation; the [...] Read more.

This paper presents two novel automated optimization approaches. The first one proposes a framework to optimize wind turbine blades by integrating multidisciplinary 3D parametric modeling, a physics-based optimization scheme, the Inverse Blade Element Momentum (IBEM) method, and 3D Reynolds-averaged Navier–Stokes (RANS) simulation; the second method introduces a framework combining 3D parametric modeling and an integrated goal-driven optimization together with a 4D Unsteady Reynolds-averaged Navier–Stokes (URANS) solver. In the first approach, the optimization toolbox operates concurrently with the other software packages through scripts. The automated optimization process modifies the parametric model of the blade by decreasing the twist angle and increasing the local angle of attack (AoA) across the blade at locations with lower than maximum 3D lift/drag ratio until a maximum mean lift/drag ratio for the whole blade is found. This process exploits the 3D stall delay, which is often ignored in the regular 2D BEM approach. The second approach focuses on the shape optimization of individual cross-sections where the shape near the trailing edge is adjusted to achieve high power output, using a goal-driven optimization toolbox verified by 4D URANS Computational Fluid Dynamics (CFD) simulation for the whole rotor. The results obtained from the case study indicate that (1) the 4D URANS whole rotor simulation in the second approach generates more accurate results than the 3D RANS single blade simulation with periodic boundary conditions; (2) the second approach of the framework can automatically produce the blade geometry that satisfies the optimization objective, while the first approach is less desirable as the 3D stall delay is not prominent enough to be fruitfully exploited for this particular case study. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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30 pages, 7785 KiB

Open AccessFeature PaperArticle

The Hydrodynamics and Mixing Performance in a Moving Baffle Oscillatory Baffled Reactor through Computational Fluid Dynamics (CFD)

by Hamid Mortazavi and Leila Pakzad

Processes 2020, 8(10), 1236; https://doi.org/10.3390/pr8101236 - 2 Oct 2020

Cited by 11 | Viewed by 4242

Abstract

Oscillatory baffled reactors (OBRs) have attracted much attention from researchers and industries alike due to their proven advantages in mixing, scale-up, and cost-effectiveness over conventional stirred tank reactors (STRs). This study quantitatively investigated how different mixing indices describe the mixing performance of a [...] Read more.

Oscillatory baffled reactors (OBRs) have attracted much attention from researchers and industries alike due to their proven advantages in mixing, scale-up, and cost-effectiveness over conventional stirred tank reactors (STRs). This study quantitatively investigated how different mixing indices describe the mixing performance of a moving baffle OBR using computational fluid dynamics (CFD). In addition, the hydrodynamic behavior of the reactor was studied, considering parameters such as the Q-criterion, shear strain rate, and velocity vector. A modification of the Q-criterion showed advantages over the original Q-criterion in determination of the vortices’ locations. The dynamic mesh tool was utilized to simulate the moving baffles through ANSYS/Fluent. The mixing indices studied were the velocity ratio, turbulent length scale, turbulent time scale, mixing time, and axial dispersion coefficient. We found that the oscillation amplitude had the most significant impact on these indices. In contrast, the oscillatory Reynolds number did not necessarily describe the mixing intensity of a system. Of the tested indices, the axial dispersion coefficient showed advantages over the other indices for quantifying the mixing performance of a moving baffle OBR. Full article

(This article belongs to the Special Issue Complex Fluid Dynamics Modeling and Simulation)

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