Discrete Phase Research Articles

Magnetic nanoparticle interaction with a hydrogel in an oscillating magnetic field

A study was conducted of the effect of superparamagnetic nanoparticles on a hydrogel in the presence of an oscillating magnetic field directed tangent to the hydrogel surface. The oscillating magnetic field causes the particles to oscillate laterally in the hydrogel, with some of the particles adhering to the hydrogel matrix and other particles moving freely through the hydrogel pore spaces. The analysis was performed for a three-phase matrix-water-particles model, in which the solvent (water) and hydrogel matrix are interacting continua and the particles are a discrete phase. The study examined the effect of fluid elasticity on wave propagation due to the no-slip boundary condition acting under the transversely oscillating magnetic field. A memory effect within the fluid results in a deviation of the minimum and maximum shear rates observed in one half of the oscillation period from those observed in the other half of the oscillation period. The behavior of the hydrogel with different values of the governing dimensionless parameters was assessed. The matrix Reynolds number, the Deborah number, and the ratio of matrix relaxation to retardation times were all observed to have significant influence on the hydrogel viscoelastic response and on the wave propagation within the hydrogel. The phase difference between the water and matrix oscillations is strongly influenced by the phase interaction force coefficient, the Deborah number, and the ratio of free to captured particles. The system is found to approach an asymptotic state at a high Deborah number, which is independent of the value of the Deborah number.

Robust cascade controller design for discrete minimum phase system using a novel data-driven virtual reference feedback tuning approach

Robust cascade controller design for discrete minimum phase system using a novel data-driven virtual reference feedback tuning approach

Robust cascade controller design for discrete minimum phase system using a novel data-driven virtual reference feedback tuning approach

Robust cascade controller design for discrete minimum phase system using a novel data-driven virtual reference feedback tuning approach

A comprehensive study on the design and computational analysis of an air swirl burner

This paper presents a comprehensive study on optimizing the design of a vane-type air swirl burner, along with a computational analysis comparing the combustion of diesel and hydrogen fuel within the same burner. For the combustion simulations, a coupled approach was employed involving a Lagrangian approach with the Discrete Phase Model to track the trajectories of fuel particles providing a comprehensive understanding of the particulate dynamics within the system. This research aimed to analyze hydrogen's potential as a sustainable energy carrier in comparison to its conventional counterparts such as diesel fuel. The results showed that the contours of hydrogen fuel revealed a well-defined and intense flame front whereas it was not the same in the case of diesel fuel which had a less intense flame front.

COLLECTION EFFICIENCY ANALYSIS AND STRUCTURAL OPTIMIZATION OF FUGITIVE FUMES FROM ALUMINUM ELECTROLYSIS BASED ON MULTIFIELD COUPLING

The collection of fugitive fumes from aluminum electrolysis is a major technical issue that has hampered the green production of aluminum electrolysis for a long time. The collection process of fugitive fumes from aluminum electrolysis also is a complex flow process containing multifield coupling. There are various structural parameters that affect the collection efficiency in this procedure. In this paper, a multifield coupling simulation method based on a computational fluid dynamics discrete phase model was developed. To achieve the best collection efficiency, a multifactor interaction effect analysis was executed with the length <i>L<sub>W</sub></i> of the exhaust hood edge, the vertical distance <i>D<sub>H</sub></i> between the exhaust hood and the surface of the residual carbon block, and the horizontal distance <i>D<sub>L</sub></i> between the exhaust hood and the surface of the residual carbon block as the optimization parameters. The response surface methodology and multi-island genetic algorithm were used to carry out the optimization study of maximizing the collection efficiency. The results showed that for the flue gas and dust collection efficiency, the <i>D<sub>H</sub></i> contributes the most, followed by the <i>L<sub>W</sub></i>, and the <i>D<sub>L</sub></i> is the smallest; when the <i>L<sub>W</sub></i> is 748.99 mm, <i>D<sub>H</sub></i> is 224.06 mm, and <i>D<sub>L</sub></i> is 227.66 mm, it can effectively improve the flue gas and dust collection efficiency, in which the flue gas collection efficiency is increased by 6.01% and the dust collection efficiency is increased by 5.97%.

Influence of stationary porous media on fluid flow

The work examines the flow of an incompressible fluid containing a porous medium. A porous body is formed through various mechanisms. To describe the flow, a single equation is used that describes the flow of fluid in the porous and free zone. The flow is simulated based on Rakhmatulin’s two-speed model, in a laminar mode with zero speed of a discrete phase. The results of numerical simulation of the hydrodynamic features of a two-dimensional viscous flow are presented. The Kozeny-Karman relation is used as the force of interaction with the porous layer. Computational experimental methods are used to study the effects of nonuniformity of the fluid velocity field arising from a porous body. For the numerical implementation of the resulting equation, which is a generalization of the Navier-Stokes equation, a SIMPLE-like algorithm with corresponding generalizations was used. A single algorithm is used for the entire area, without identifying the free and porous zones.

Optimal Configuration of Reconfigurable Intelligent Surfaces with Arbitrary Discrete Phase Shifts

Optimal Configuration of Reconfigurable Intelligent Surfaces with Arbitrary Discrete Phase Shifts

Multi-scale analysis of respiratory droplets transport within the breathing cloud

Infectious diseases are transmitted primarily through pathogen laden droplets commonly exhaled during respiratory events such as breathing, coughing, or sneezing. The transport and evaporation of droplets are governed by the fundamental laws of fluid mechanics and convection-diffusion. From these, analytical models can be created helping in better understanding pathogens transmission from a mechanical perspective. The droplet transport within the humid air breath cloud and the local ventilation are crucial for accurately predicting the droplet fate. Different levels of complexity are possible for modelling the breath cloud, from simple 1D models to complex unsteady 3D simulations including discrete phase models for the droplets simulation. The former are too simple to capture the fluid dynamics of intermittent jets in detail, while the latter are too computationally expensive. The current work presents a novel multi-scale approach where an analytical model of the droplet transport and evaporation is coupled to unsteady CFD simulations of warm humid puffs of exhaled air. The proposed model has the advantage of the accuracy of an analytical model and the computational cost of a relatively standard unsteady CFD simulation, and can be used to predict the trajectory of the exhaled droplets for a variety of respiratory events.

Influence of secondary air on the flow field of NGZF classifier

Aiming at the problems of uneven material dispersion of traditional air classifier, NGZF classifier with downward air inlet fabric method is designed. In order to investigate the classification law of the classifier and the effect of secondary air on the flow field of the classifier, this paper utilizes ANSYS-Fluent19.2 software to simulate the internal flow field and conducts material experiments using the response surface method. The simulation results demonstrate that with the rise of the secondary air volume, the overall flow field distribution tends to be appropriate, and the washing flow field created by the secondary air does not interfere with the primary flow field. However, when the secondary air is too big, it will generate turbulence in the axial velocity in the guide cone zone. The discrete phase model (DPM) indicated that the secondary air would re-screen the misclassified fine particles. Response surface experiments with calcined petroleum coke showed that by setting the cut particle size at 50 ?m and maximizing the classification accuracy, the ideal operating parameters were a rotor speed of 1037.4 rpm, a primary air volume of 429.6 m3?h-1, and a secondary air volume of 50.2 m3?h-1. This work not only provides a novel approach for the design and development of airflow classifiers but also gives theoretical direction for their implementation in industrial production.

Joint Design of Doppler Resilient Unimodular Discrete Phase Sequence Waveform and Receiving Filter for Multichannel Radar

Joint Design of Doppler Resilient Unimodular Discrete Phase Sequence Waveform and Receiving Filter for Multichannel Radar

Numerical Simulation of Pyrethrin Aerosol Deposition

Highlights A steady state, laminar CFD model was developed to simulate the airflow inside an aerosol exposure chamber. The CFD model predicted the droplet tracks and deposition of various sizes of aerosol droplets. Larger aerosol droplets had higher deposition efficiency. A Higher flow rate, but still within the laminar flow regime, caused lower deposition efficiency for all droplet sizes. Abstract. Aerosol insecticides (e.g., pyrethrin) are widely used for the control of stored products insects inside food facilities. To optimize pyrethrin aerosol application, computational fluid dynamics (CFD) was used to predict airflow and aerosol transport inside a vertical flow aerosol exposure chamber operated under laminar flow conditions. A discrete phase model in ANSYS FLUENT 2021 R1 was developed, and simulations were conducted to track pyrethrin droplets of various diameters (0.1 to 20 µm) and determine their deposition onto Petri dishes located near the center of the chamber. The deposition efficiency of the different aerosol droplet sizes and the effect of two flow rates (5 × 10-4 m3 s-1 and 4 × 10-4 m3 s-1) on deposition efficiency were determined. The results showed that the predicted deposition of pyrethrin aerosol increased with increasing droplet size, largely due to inertial and gravitational effects. Deposition efficiencies decreased with the higher flow rate—with 0.1% to 96.6% predicted deposition efficiencies for the low flow rate and 0.1% to 93.8% for the high flow rate. Results of this study can be used to improve aerosol application methods for stored product insect control. Keywords: Aerosol deposition, Aerosol insecticide, Computational fluid dynamics, Confused flour beetle, Deposition efficiency, Discrete phase model, Numerical simulation, Particle tracking, Pyrethrins, Stored product insect.

STAR-RIS Assisted Wireless Communications With Discrete Phase Shifter

STAR-RIS Assisted Wireless Communications With Discrete Phase Shifter

Signal Power Maximization and Channel Estimation for mmWave Communication Systems Aided by RIS with Discrete Phase Shifts

Signal Power Maximization and Channel Estimation for mmWave Communication Systems Aided by RIS with Discrete Phase Shifts

Received Power Maximization Using Nonuniform Discrete Phase Shifts for RISs With a Limited Phase Range

Received Power Maximization Using Nonuniform Discrete Phase Shifts for RISs With a Limited Phase Range

Fluid flow, slag entrainment, and composition evolution of slag inclusions during vacuum degassing refining

A multiphase mathematical model was established to study the fluid flow, the open-eye formation, and the residence time of slag inclusions in a bottom argon-blowing ladle. The fluid flow was solved using the Eulerian-Lagrangian multiphase approach, and the interface between different phases was described using the Volume of Fluid (VOF) model. The motion of argon bubbles and slag inclusions was tracked with the method of the discrete phase model (DPM). Moreover, the composition transformation of slag inclusions was predicted by employing a kinetic model based on the coupled reactions model. Numerical results show that the flow of the molten steel and the open-eye of the molten slag were sensitive to the argon blowing rate. The larger argon blowing rate expanded the volume of the plume and the area of the open-eye. Slag droplets were considered to move with the steel to the region away from the open-eye and then entrained into the steel to form slag inclusions as there was barely any downward velocity around the open-eye. Most slag inclusions were able to be removed immediately after the entrainment, while there still were some slag inclusions retaining in the steel for as long as thousands of seconds. The composition of slag inclusions had an apparent transformation due to reactions with the steel. The content of SiO2 and MgO in slag inclusions had a decrease while that of Al2O3 rose remarkably. The variation of SiO2 content occurred in the early one minute and the MgO content reduced gradually from 7.34wt% to 1.12wt% in 10 min. The composition transformation of slag inclusions was basically completed within 10 min in the current case.

Notice of Violation of IEEE Publication Principles: An Efficient Nonlinear Quantized Constant Envelope Precoding for Massive MU-MIMO Systems

Notice of Violation of IEEE Publication Principles <BR><BR>"An Efficient Nonlinear Quantized Constant Envelope Precoding for Massive MU-MIMO Systems," <BR>by R. Liang, H. Li, W. Zhang, C. Liu and Y. Guo, <BR>in IEEE Systems Journal, Early Access <BR><BR>After a careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. <BR><BR>This paper contains content from the papers cited below. Credit notices were used, but due to the absence of quotation marks or offset text, the copied content is not clearly referenced or specifically identified. <BR><BR>"VLSI Design of a 3-bit Constant-Modulus Precoder for Massive MU-MIMO," <BR>by O. Castañeda, S. Jacobsson, G. Durisi, T. Goldstein and C. Studer, <BR>in the Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS), May 2018 <BR><BR>"Quantized Precoding for Massive MU-MIMO," <BR>by S. Jacobsson, G. Durisi, M. Coldrey, T. Goldstein and C. Studer, <BR>in IEEE Transactions on Communications, vol. 65, no. 11, pp. 4670-4684, November 2017 <BR><BR> <br/> Massive multiuser multiple-input&#x2013;multiple-output (MU-MIMO) systems are foreseen as the key technology in next-generation wireless communication systems. However, many radio-frequency (RF) chains will require high power consumption and lots of hardware cost. One of the practical solutions is using low-resolution discrete phase shifters (PSs) for each antenna and RF chain. This article designs a nonlinear quantized constant envelope precoding algorithm for MU-MIMO systems with low-resolution discrete PS at the base station. In this algorithm, the quantized constant envelope precoding problem is presented as a nonconvex optimization problem. The multiuser interference is minimized by solving the optimal precoded vector and the associated precoding factors. First, we consider relaxing the nonconvex constraint on the 1-bit quantized constant envelope precoding to a continuous set of convex constraints on the unit circle. Afterwards, the semidefinite relaxation method is used to tackle the equivalent 1-bit quantized precoding problem. We further extend the algorithm to provide multi-bit quantized constant envelop precoding. Finally, the simulations are carried out under various conditions and compared with the most advanced precoding methods. The results demonstrate that this algorithm achieves a comparable performance to the existing precoding methods. At the same time, the corresponding performance-complexity tradeoff is more conducive to the expansion of the proposed algorithm to the multibit case.

Study on Oil-Gas Separation Characteristics of Gearbox Sealing System of High-Speed Electric Multiple Unit

Based on the discrete phase model (DPM) and droplet-wall collision model, this paper analyzes the oil-gas separation characteristic and sealing performance of a gearbox sealing system. The results show that the airflow drag force and oil droplet inertia force affect the oil-gas separation efficiency of the sealing system. Furthermore, larger oil droplet diameter leads to a higher separation efficiency and lower outlet back pressure reduces the separation efficiency of smaller diameter oil droplet and increases the separation efficiency of larger diameter droplet. For oil droplet with an intermediate diameter, the separation efficiency first decreases and then increases with the reduction in back pressure.

气固耦合条件下多孔热风式茶叶杀青理条机数值模拟与性能试验

The gas–solid coupling of a porous hot-air tea de-enzyming and carding machine was studied by means of computational fluid dynamics and discrete element coupling. In the numerical model, the discrete phase of tea particles was simulated using Rocky-DEM software, while the gas phase was described by ANSYS Fluent software. A mathematical model of the movement characteristics of tea particles in air was established according to the principle of fluid mechanics, to carry out dynamic analysis of tea particles’ movement process and derive how the motion of gas and tea particles is governed. Three sets of prototype tests were carried out on the basis of the design and simulation, and the average of their results taken. This showed that the hourly output of the test prototype was 3.89 kg/h, the bar-type rate was 89.14%, the de-enzyming moderation rate was 91.67%, and the average value of the measured effective operating temperature of the pot slot was 189 °C. The performance of the prototype was also tested and analyzed. After conducting a tea sensory evaluation expert appraisal, the sensory evaluation indices of the prototype-processed tea satisfied all current market requirements, being superior to those of the conventional de-enzyming and carding machine. The quality of the finished tea also met the agronomic standards and the operational requirements of the de-enzyming and carding machine.

Study of the droplet size of the discrete phase of a fuel-water emulsion

In the era of increasing care for the earth's climate, numerous scientific studies are being conducted looking for alternative fuels with reduced emissions. One is a fuel-water emulsion, which has a particularly positive effect on NOx emissions. The article presents tests carried out on a fuel-water emulsion containing from 3% to 15% water and from 1% to 3% emulsifier, aiming to determine the microscopic properties of the developed emulsion. The study focused on the influence of the composition of the tested emulsion, the mixing time of its components and the influence of pumping it through the fuel pump on the size of water droplets of the discrete phase.

Study on reactivity characteristic of TDA droplet group with gaseous phosgene for preparing TDI

Toluene diisocyanate stands as a pivotal chemical, predominantly synthesized through the phosgenation reaction between toluene diamine and phosgene. To address the inherent limitations of existing phosgenation methods, we pioneered a novel phosgenation reaction based on flash atomization and confirmed its feasibility with preliminary theoretical calculations. This manuscript delves deeper into the superiority of this method and refines its reaction parameters. By integrating the discrete phase model with the Eulerian model, we studied the reaction dynamics of droplet sprays, exploring the effects of spray velocity, droplet size, phosgene temperature, and particle size distribution on the reaction. Our results highlight that, with a mean droplet diameter of 70 μm and a spray velocity of 40 m/s, an impressive reaction yield of 97.4 % can be achieved. This research enriches our understanding of the gas–liquid two-phase phosgenation method, setting the stage for its future exploration and potential applications in Toluene diisocyanate and other isocyanate industry.