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Simulation of the spatio-temporal evolution of the electron energy distribution function in a pulsed hollow-cathode discharge

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Plasma Science and Technology 2023年第3期25卷 87-94页

作者： N A ASHURBEKOV K O ImINOV K m RABADANOV g S SHAKHSINOV m Z ZAKARYAEVA m B KURBANgADZHIEVA Dagestan State University Department of Physics Harbin Institute of Technology Institute of Physics Dagestan Federal Research CenterRussian Academy of Sciences

This article presents the 2D simulation results of a nanosecond pulsed hollow cathode discharge obtained through a combination of fluid and kinetic *** spatio-temporal evolution of the electron energy distribution function(EEDF)of the plasma column and electrical characteristics of the nanosecond pulsed hollow cathode discharge at a gas pressure of 5 Torr are *** results show that the discharge development starts with the formation of an ionization front at the anode *** ionization front splits into two parts in the cathode cavity while propagating along its lateral *** ionization front formation leads to an increase in the fast isotropic EEDF component at its front,as well as in the anisotropic EEDF *** accelerated electrons enter the cathode cavity,which significantly contributes to the formation of the highenergy EEDF component and EEDF anisotropy.

关键词： pulsed nanosecond discharge electron energy distribution fuinction hollow cathode electron kinetics gas discharge

Transient Non-Thermal mobility of CO for CO-NO Catalytic Reaction on Square Lattice： monte Carlo Simulation

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Chinese Physics Letters 2008年第4期25卷 1482-1485页

作者： m. Khalid A. U. Qaisrani m. g. Ullah Department of Physics Gomal University Dera Ismail Khan Pakistan

We study a model based on precursor mechanism for CO-NO catalytic reaction on square lattice with monte Carlo simulation. The precursor mechanism clearly demonstrates its impact on the phase diagram. The steady reactive state （SRS） gets established. The width of reactive region increases by increasing the range of precursor mobility. When the precursor mobility is increased to third-nearest neighbourhood, the second-order transition disappears.

关键词： ELEY-RIDEAL PROCESS PHASE-DIAgRAm HETEROgENEOUS CATALYSIS PRECURSOR mECHANISm HEXAgONAL SURFACES CUBIC STRUCTURE SUBSURFACE mODEL CHEmISORPTION TRANSITIONS

Instability Analysis of Positron-Acoustic Waves in a magnetized multi-Species Plasma

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Communications in Theoretical Physics 2017年第4期67卷 458-466页

作者： m.A.Hossen m.g.Shah m.R.Hossen A.A.mamun Department of Physics Jahangirnagar UniversitySavarDhaka-1342Bangladesh Department of Physics Hajee Mohammad Danesh Science and Technology UniversityDinajpur-5200Bangladesh Department of general Educational Development Daffodil International UniversitySukrabadDhaka-1207Bangladesh

The nonlinear propagation of electrostatic excitations and their multi-dimensional instability in a magnetized, degenerate electron-positron-ion(EPI) plasma system(containing inertial cold positrons, relativistic degenerate electrons and hot positrons, and negatively charged immobile heavy ions) are theoretically investigated. The reductive perturbation method is employed to derive the Zakharov–Kuznetsov equation which admits a localized solitary wave solution for small but finite amplitude limit, and the multi-dimensional instability of the positron acoustic solitary waves(PASWs) is studied by the small-k perturbation expansion method. It is found that the basic characteristics(viz. phase speed, amplitude, width) of the PASWs are significantly affected by the degree of obliqueness, relativistic degeneracy,and plasma particle number densities. The instability criterion and its growth rate, which are depending on the magnetic field and the propagation directions of both the PASWs, and their perturbation modes are discussed. The present analysis can be helpful in understanding the nonlinear phenomenon in dense astrophysical as well as space plasma systems,especially in pulsar environments.

关键词： instability analysis solitary waves magnetized plasma degeneracy relativistic effect

Scalable Distributed Sensor Fault Diagnosis for Smart Buildings

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IEEE/CAA Journal of Automatica Sinica 2020年第3期7卷 638-655页

作者： Panayiotis m.Papadopoulos Vasso Reppa marios m.Polycarpou Christos g.Panayiotou IEEE KIOS Research and Innovation Center of Excellence Department of Electrical and Computer EngineeringUniversity of CyprusNicosia 1678Cyprus Department of maritime and Transport Technology Delft University of TechnologyDelft2628 CDThe Netherlands

The enormous energy use of the building sector and the requirements for indoor living quality that aim to improve occupants' productivity and health, prioritize Smart Buildings as an emerging technology. The Heating, Ventilation and Air-Conditioning(HVAC) system is considered one of the most critical and essential parts in buildings since it consumes the largest amount of energy and is responsible for humans comfort. Due to the intermittent operation of HVAC systems, faults are more likely to occur, possibly increasing eventually building's energy consumption and/or downgrading indoor living quality. The complexity and large scale nature of HVAC systems complicate the diagnosis of faults in a centralized framework. This paper presents a distributed intelligent fault diagnosis algorithm for detecting and isolating multiple sensor faults in large-scale HVAC *** the HVAC system as a network of interconnected subsystems allows the design of a set of distributed sensor fault diagnosis agents capable of isolating multiple sensor faults by applying a combinatorial decision logic and diagnostic reasoning. The performance of the proposed method is investigated with respect to robustness, fault detectability and scalability. Simulations are used to illustrate the effectiveness of the proposed method in the presence of multiple sensor faults applied to a 83-zone HVAC system and to evaluate the sensitivity of the method with respect to sensor noise variance.

关键词： Building automation fault diagnosis fault location smart homes

Hydromagnetic oscillatory Couette flow in rotating system with induced magnetic field

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Applied mathematics and mechanics(English Edition) 2014年第10期35卷 1331-1344页

作者： g.S.SETH S.m.HUSSAIN S.SARKAR Department of Applied mathematics Indian School of Mines Department of mathematics O.P.Jindal Institute of Technology

This paper presents a study of hydromagnetic Couette flow of an incompress- ible and electrically conducting fluid between two parallel rotating plates, one of which is oscillating in its own plane. A uniform transverse magnetic field is used, and the induced magnetic field is taken into account. The exact solution to the governing equations is obtained in a closed form. The solution to the problem in the case of vanishing and small finite magnetic Prandtl numbers is also derived from the general solution. The asymp- totic behavior of the solution for large values of the frequency parameter is analyzed to gain some physical insights into the flow pattern. Expressions for the shear stress at both the oscillatory and stationary plates due to primary and secondary flows and mass flow rate in the primary and secondary flow directions are also obtained. The results of the fluid velocity and the induced magnetic field are presented. The shear stresses on the plates due to the primary and secondary flows and the corresponding mass flow rates are presented in a tabular form.

关键词： magnetic interaction parameter Ekman number frequency parameter,hydromagnetic Stokes-Ekman boundary layer magnetic diffusion boundary layer

Particle mixing rates using the two-fluid model

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Particuology 2018年第1期16卷 13-26页

作者： m. Banaei N.g. Deen m. van Sint Annaland J.A.m. Kuipers multiphase Reactors group Deportment of Chemical Engineering & Chemistry Eindhoven University of Technology 5600 MB Eindhoven The Netherlands Dutch Polymer Institute (DPI) 5600 AX Eindhoven The Netherlands multiphase and Reactive Flows group Department of Mechanical Engineering Eindhoven University of Technology 5600 MB Eindhoven The Netherlands

In this work, a new methodology is introduced to calculate the solids mixing rate in dense gas-fluidized beds using the two-fluid model. The implementation of this methodology into an existing two-fluid model code was carefully verified. The solids phase continuity equation was satisfied using our method, and the sensitivity of the computational results to the time step, computational cell size, and discretization scheme was investigated to determine the optimal simulation settings. Using these simulation settings, the degree of solids mixing was observed to rapidly （exponentially） increase with increasing operating pressure and linearly decrease with increasing bed diameter. Our novel methodology can be applied to analyze mixing processes in large lab-scale beds as an alternative to existing time-consuming simulation techniques such as computational fluid dynamics combined with the discrete element model.

关键词： gas-solid fluidized bed Simulation Two-fluid model Solids mixing Pressure Scale up

The dynamics of a nanosecond gas discharge development with an extended slot cathode in argon

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Plasma Science and Technology 2020年第12期22卷 78-88页

作者： N A ASHURBEKOV K O ImINOV g S SHAKHSINOV m Z ZAKARYAEVA K m RABADANOV Dagestan State University Faculty of PhysicsMakhachkala 367000Russia Institute of Physics DFRC of RASMakhachkala 367015Russia

The article presents the results of an experimental study and numerical modelling for the formation and development dynamics of a high-voltage transverse nanosecond discharge generated by a slot cathode in an argon medium at a pressure range of 1–10 Torr. Numerical modelling was carried out under similar experimental conditions for the processes of formation and propagation of ionisation waves, electron density distribution, excited atom and average electron energy in the discharge gap, including the cavity inside the cathode. At a pressure of p=1 Torr, a classical version of a high-voltage discharge is demonstrated to take place with no penetration of the plasma into the cathode cavity and no observed hollow cathode effect. An increase in gas pressure to 5 Torr leads to a penetration of plasma into the cathode cavity with the formation of a cathodic potential drop(CPD) region. Electrons emitted from the side surfaces of the cavity pass through the CPD region without collisions, oscillate inside the cathode cavity;the hollow cathode effect is fully manifested. At р=10 Torr, the modelling results qualitatively coincide with the results at р=5 Torr;in this case, however, hardly any accelerated electrons are observed in the gap between the electrodes, due to their energetic relaxation both inside the cathode cavity and when exiting from it. In both cases, the plasma structure formed at the exit of the cathode cavity involves a concentration of charged particles an order of magnitude higher than that in the rest of the gap, leading to a self-limiting discharge current effect. The results of the numerical modelling are in good agreement with experimental data.

关键词： nanosecond gas discharge numerical simulation argon excited atoms

Electro-magneto-hydrodynamic flow of couple stress nanofluids in micro-peristaltic channel with slip and convective conditions

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Applied mathematics and mechanics(English Edition) 2021年第4期42卷 593-606页

作者： K.RAmESH m.g.REDDY B.SOUAYEH Department of mathematics Symbiosis Institute of TechnologySymbiosis International(Deemed University)Pune 412115India Department of mathematics Acharya Nagarjuna UniversityOngole CampusOngole 523001India Department of Physics College of ScienceKing Faisal UniversityAl-Ahsa 31982Saudi Arabia Laboratory of Fluid mechanics Physics DepartmentFaculty of Sciences of TunisUniversity of Tunis El ManarTunis 2092Tunisia

This study explores the effects of electro-magneto-hydrodynamics,Hall currents,and convective and slip boundary conditions on the peristaltic propulsion of nanofluids(considered as couple stress nanofluids)through porous symmetric *** phenomena of energy and mass transfer are considered under thermal radiation and heat source/*** governing equations are modeled and non-dimensionalized under appropriate dimensionless *** resulting system is solved numerically with mATHEmATICA(with an in-built function,namely the Runge-Kutta scheme).graphical results are presented for various fluid flow quantities,such as the velocity,the nanoparticle temperature,the nanoparticle concentration,the skin friction,the nanoparticle heat transfer coefficient,the nanoparticle concentration coefficient,and the trapping *** results indicate that the nanoparticle heat transfer coefficient is enhanced for the larger values of thermophoresis ***,an intriguing phenomenon is observed in trapping:the trapped bolus is expanded with an increase in the Hartmann ***,the bolus size decreases with the increasing values of both the Darcy number and the electroosmotic parameter.

关键词： peristalsis magnetohydrodynamics(mHD) nanofluid Hall current porous medium thermal radiation

CFD modeling of immiscible liquids turbulent dispersion in Kenics static mixers: Focusing on droplet behavior

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Chinese Journal of Chemical Engineering 2020年第2期28卷 348-361页

作者： m.m.Haddadi S.H.Hosseini D.Rashtchian g.Ahmadi Chemical and Petroleum Engineering Department Sharif University of TechnologyTehranIran Department of Chemical Engineering Ilam UniversityIlam 69315–516Iran Department of mechanical and Aeronautical Engineering Clarkson UniversityPotsdamNY 13699-5725USA

The present study is concerned with the computational fluid dynamics(CFD)simulation of turbulent dispersion of immiscible liquids,namely,water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 *** study the droplet size distribution(DSD),the Eulerian formulation incorporating a population balance model(PBm)was *** the Eulerian–Lagrangian approach,a discrete phase model(DPm)in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution(RTD)of *** both approaches,a shear stress transport(SST)k-ωturbulence model was *** validation purposes,the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor,Sauter mean diameter and the mean residence *** reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean *** addition,the influence of important geometrical and operational parameters,including the number of mixing elements and Weber number,was *** was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.

关键词： CFD Liquid–liquid dispersion Kenics static mixer Eulerian–Eulerian approach Eulerian–Lagrangian approach