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Computational simulations of near-continuum gas flow using Navier-stokes-Fourier equations with slip and jump conditions based on the modal discontinuous Galerkin method

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Advances in Aerodynamics 2020年第1期2卷 145-181页

作者： T.Chourushi A.rahimi s.singh r.s.myong school of Mechanical and Aerospace Engineering and ACTrC&reCAPT Gyeongsang National UniversityJinjuGyeongnam 52828South Korea school of Physical and Mathematical sciences Nanyang Technological University21 Nanyang LinkSingapore 637371Singapore

Blunt-body configurations are the most common geometries adopted for non-lifting re-entry *** re-entry vehicles experience different flow regimes during flight due to drastic changes in atmospheric *** conventional Navier-stokes-Fourier equations with no-slip and no-jump boundary conditions may not provide accurate information regarding the aerothermodynamic properties of blunt-bodies in flow regimes away from the *** addition,direct simulation Monte Carlo method requires significant computational resources to analyze the near-continuum flow *** overcome these shortcomings,the Navier-stokes-Fourier equations with slip and jump conditions were numerically solved.A mixed-type modal discontinuous Galerkin method was employed to achieve the appropriate numerical *** computational simulations were conducted for different blunt-body configurations with varying freestream Mach and Knudsen *** results show that the drag coefficient decreases with an increased Mach number,while the heat flux coefficient *** the other hand,both the drag and heat flux coefficients increase with a larger Knudsen ***,for an Apollo-like blunt-body configuration,as the flow enters into non-continuum regimes,there are considerable losses in the lift-to-drag ratio and stability.

关键词： Near-continuum flow Discontinuous Galerkin method slip and jump conditions

A remark on Leray's Problem on stationary Navier–stokes Flows with Large Fluxes in Infinite Cylindrical Domains

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Acta Mathematica sinica,English series 2015年第10期31卷 1571-1581页

作者： myong-Hwan rI Institute of Mathematics State Academy of SciencesPyongyang DPR Korea

We consider Leray＇s problem on stationary Navier stokes flows with arbitrary large fluxes in an unbounded cylinder with several exits to infinity. For a stationary Navier stokes flow with large fluxes in the unbounded cylinder, we prove that, if the difference between the pressure of the main flow and the pressure of the Poiseuille flow with the same flux in a branch of the cylinder remains bounded at ｜x｜→∞, then the flow behaves at infinity of the branch like the Poiseuille flow.

关键词： Leray's problem Navier-stokes equations large flux unbounded cylindrical domains

regularity for 3D Navier–stokes Equations Based on Energy Distribution at Wavenumber Bands

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Acta Mathematica sinica,English series 2019年第8期35卷 1377-1392页

作者： myong-Hwan rI Institute of Mathematics State Academy of SciencesDPR Korea

We present some regularity criteria for the Leray–Hopf weak solutions to the Cauchy problem for 3D Navier–stokes equations based on energy distribution at wavenumber bands. We show sufficient conditions for regularity based on the ratios of energy dissipation rates at sufficiently high wavenumber bands and neighboring medium wavenumber bands. Moreover, we give a regularity criterion based on relations between energy at high and low wavenumber bands.

关键词： Navier-stokes equations global regularity energy transfer

MAXIMAL L^(1)-rEGULArITY OF GENErATOrs FOr BOUNDED ANALYTIC sEMIGrOUPs IN BANACH sPACEs

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Acta Mathematica scientia 2022年第4期42卷 1261-1272页

作者： myong-Hwan rI reinhard FArWIG Institute of Mathematics State Academy of SciencesPyongyangDPR Korea Department of Mathematics Darmstadt University of TechnologyGermany

In this paper,we prove that the generator of any bounded analytic semigroup in(θ,1)-type real interpolation of its domain and underlying Banach space has maximal L^(1)-regularity,using a duality argument combined with the result of maximal continuous *** an application,we consider maximal L^(1)-regularity of the Dirichlet-Laplacian and the stokes operator in inhomogeneous B_(q),^(s),1-type Besov spaces on domains of r^(n),n≥2.

关键词： Maximal L^(1)-regularity sectorial operator stokes operator

OPErATOr-VALUED FOUrIEr MULTIPLIEr THEOrEMs ON TrIEBEL sPACEs

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Acta Mathematica scientia 2005年第4期25卷 599-609页

作者：步尚全 Kim Jin-myong Department of Mathematical science University of Tsinghua Beijing 100084 China Department of Mathematics University of Kim Il Sung DPR KoreaDepartment of Mathematical Science University of Tsinghua Beijing 100084 China

The authors establish operator-valued Fourier multiplier theorems on Triebel spaces on r^N, where the required smoothness of the multiplier functions depends on the dimension N and the indices of the Triebel spaces. This is used to give a sufficient condition of the maximal regularity in the sense of Triebel spaces for vector-valued Cauchy problems with Dirichlet boundary conditions.

关键词： Operator-valued Fourier multiplier vector-valued Triebel space Fourier type vector-valued maximal inequality maximal regularity

Fundamentals and comprehensive insights on pulsed laser synthesis of advanced materials for diverse photo-and electrocatalytic applications

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Light(science & Applications) 2022年第9期11卷 2018-2064页

作者： Jayaraman Theerthagiri K Karuppasamy seung Jun Lee r.shwetharani Hyun-seok Kim s.K Khadheer Pasha Muthupandian Ashokkumar myong Yong Choi Core-Facility Center for Photochemistry&Nanomaterials Department of ChemistryResearch Institute of Natural SciencesGyeongsang National UniversityJinju 52828Republic of Korea Division of Electronics and Electrical Engineering Dongguk University-SeoulSeoul 04620Republic of Korea Centre for Nano and Material sciences Jain UniversityJain Global CampusKanakapuraBangalore 562112 KarnatakaIndia Department of Physics Vellore Institute of Technology(Amaravati Campus)Amaravati522501 GunturAndhra PradeshIndia school of Chemistry University of MelbourneParkville CampusMelbourneVIC 3010Australia

The global energy crisis is increasing the demand for innovative materials with high purity and functionality for the development of clean energy production and *** development of novel photo-and electrocatalysts significantly depends on synthetic techniques that facilitate the production of tailored advanced *** emerging use of pulsed laser in liquid synthesis has attracted immense interest as an effective synthetic technology with several advantages over conventional chemical and physical synthetic routes,including the fine-tuning of size,composition,surface,and crystalline structures,and defect densities and is associated with the catalytic,electronic,thermal,optical,and mechanical properties of the produced ***,we present an overview of the fundamental understanding and importance of the pulsed laser process,namely various roles and mechanisms involved in the production of various types of nanomaterials,such as metal nanoparticles,oxides,non-oxides,and carbon-based *** mainly cover the advancement of photo-and electrocatalytic nanomaterials via pulsed laser-assisted technologies with detailed mechanistic insights and structural optimization along with effective catalytic performances in various energy and environmental remediation ***,the future directions and challenges of pulsed laser techniques are briefly *** review can exert practical guidance for the future design and fabrication of innovative pulsed laser-induced nanomaterials with fascinating properties for advanced catalysis applications.

关键词： insight synthesis comprehensive

Numerical study on the performance of nozzle flow for supersonic chemical oxygen-iodine lasers

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Acta Mechanica sinica 2008年第2期24卷 133-142页

作者： Zongmin Hu Junming Lā Zonglin Jiang rho-shin myong Tae-Hwan Cho LHD Institute of MechanicsCAS Beijing 100080 China research Center for Aircraft Parts Technology Geyongsang National University Jinju 660-701 South Korea

Laser performance is greatly dependent on its operating conditions due to the strong coupling among multi- physics such as gas-dynamics, chemical reaction kinetics and optics in the mixing nozzle of COIL. In this paper, 3D CFD technology is used to simulate the mixing and reactive flow of subsonic cross jet scheme at different conditions. results obtained show that the jet penetration depth plays a dominant role in the spatial distribution of small signal gains. In the case of over-penetration, unsteady flow structures are induced by impinging between the opposing jets. The optimum spatial distribution of the chemical performance cannot be obtained even if the full penetration condition is achieved through the subsonic transverse jet mixing scheme in the COIL nozzle flow.

关键词： Chemical oxygen-iodine laser (COIL) Numerical simulation small signal gains Unsteady structures

Cloud radiative Effects and Changes simulated by the Coupled Model Intercomparison Project Phase 5 Models

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Advances in Atmospheric sciences 2017年第7期34卷 859-876页

作者： sun-Hee sHIN Ok-Yeon KIM Dongmin KIM myong-In LEE Climate research Department APEC Climate Center Busan 48058 Republic of Korea school of Urban and Environmental Engineering Ulsan National Institute of Science and Technology Ulsan 44919 Republic of Korea

Using 32 CMIP5（Coupled Model Intercomparison Project Phase 5） models, this study examines the veracity in the simulation of cloud amount and their radiative effects（CrEs） in the historical run driven by observed external radiative forcing for 1850-2005, and their future changes in the rCP（representative Concentration Pathway） 4.5 scenario runs for2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CrEs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models-ACCEss1.0, ACCEss1.3, Had GEM2-CC, and Had GEM2-Es-are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble *** models project global-mean ssT warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more ssT warming show a greater increase in the net CrE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K^-1and net radiative warming of 0.46 W m^-2K^-1, suggesting a role of positive feedback to global warming.

关键词： warming cloud radiative historical CMIP interannual greenhouse ACCEss oceans seasonal

Pulsed laser interference patterning of transition-metal carbides for stable alkaline water electrolysis kinetics

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Carbon Energy 2024年第5期6卷 65-80页

作者： Yewon Oh Jayaraman Theerthagiri Ahreum Min Cheol Joo Moon Yiseul Yu myong Yong Choi Department of Chemistry(BK21 FOUr) Research Institute of Natural SciencesGyeongsang National UniversityJinjuRepublic of Korea Core−Facility Center for Photochemistry and Nanomaterials Gyeongsang National UniversityJinjuRepublic of Korea

We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in *** interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron *** defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HEr and OEr)in an alkaline ***_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical raman probes,increasing the number of active sites for OEr *** with more d-vacancies exhibits strong hydrogen binding,promoting HEr kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OEr and HEr *** results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural *** addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.

关键词： acetone H_(2)and O_(2)evolution reactions pulsed laser ablation surface defects transition-metal carbides water electrolyzer