检索结果-南通市图书馆

Effect of cha.nel sha.e on selection of time ma.ching scheme in the discontinuous Ga.erkin method for 1-D open cha.nel flow

在线全文

学校读者我要写书评

暂无评论

Journa. of Hydrodyna.ics 2015年第3期27卷 413-426页

作者： Sa.a.Za.EH Ma.EKI Fa.za. khan abdul a. Engineering Depa.tment Massachusetts Maritime Academy Glenn Depa.tment of Civil Engineering Clemson University

One-dimensiona. open cha.nel flows a.e simula.ed using the discontinuous Ga.erkin finite element method. Three different explicit time ma.ching schemes, including multistep/multista.e schemes, a.e eva.ua.ed for different cha.nel sha.es for a.cura.y a.d efficiency. The Forwa.d Euler, second-order a.a.-Ba.hforth （multistep）, a.d second-order tota. va.ia.ion diminishing （TVD） Runge-Kutta.（multista.e） time ma.ching schemes a.e utilized. The role of monotonized centra., minmod, a.d zero TVD slope limiters for ea.h of the time ma.ching scheme is investiga.ed. The numerica. flux is a.proxima.ed using HLL function. The a.cura.y a.d robustness of different time ma.ching schemes a.e eva.ua.ed for stea.y a.d unstea.y flows using a.a.ytica. a.d mea.ured da.a. The unstea.y flows include da. brea. tests with wet a.d dry beds downstrea. of the da. in prisma.ic （recta.gula., tra.ezoida., tria.gula., a.d pa.a.olic cross-sections） a.d non-prisma.ic （na.ura. river） cha.nels. The stea.y flow test involves simula.ion of hydra.lic jump in a.diverging recta.gula. cha.nel. The va.ious schemes a.e eva.ua.ed by compa.ing a.cura.y using sta.istica. mea.ures a.d efficiency using ma.imum possible time step size a. well a. CPU runtime. The second-order a.a.-Ba.hforth time ma.ching scheme is found to ha.e the best a.cura.y a.d efficiency a.ong the time stepping schemes tested.

关键词： discontinuous Ga.erkin method sha.low wa.er equa.ions time ma.ching schemes tota. va.ia.ion diminishing (TVD)slope limiter

THE MERGING OF TWO UNEQUa. a.ISYMMETRIC Pa.a.LEL TURBULENT JETS

在线全文

学校读者我要写书评

暂无评论

Journa. of Hydrodyna.ics 2012年第2期24卷 257-262页

作者： Ba.a.Ia.-GHORGHI Za.ra.Ka.E Nigel B. khan abdul a. SMITH Jeffrey R. Glenn Depa.tment of Civil Engineering Clemson University

Results of a. experimenta. study of the merging of unequa. pa.a.lel round turbulent jets a.e *** were conducted for a.jet a.ia. sepa.a.ion to nozzle dia.eter ra.io of 3.0 a.d the Reynolds numbers ra.ging from 8 000 to 15 *** dista.ce to the point where the jets a.e merged wa. mea.ured for a.ra.ge of jet source momentum flux *** different merger criteria.were used ba.ed on the mea. velocity profile,mea. pa.sive tra.er concentra.ion profile,a.d Reynolds stress *** results show tha. the concentra.ion profile merges closest to the jet sources followed by the velocity profile with the Reynolds stress profile merging furthest from the *** a.l three profiles the merge dista.ce is rela.ively insensitive to the momentum flux ra.io,consistent with previous findings for slot jets a.d buoya.t round *** mea.ured merge dista.ces a.e consistent with previously published results for equa. round jets,though the poor spa.ia. resolution of da.a.in the litera.ure mea.s tha. limited compa.ison is *** a.e no studies of unequa. jet merger currently in the litera.ure tha. could be used for compa.ison.

关键词： turbulent jet merging jets unequa. jets experiment

Thermospheric neutra. wind studies over the equa.oria. region:a.review

在线全文

学校读者我要写书评

暂无评论

Ea.th a.d Pla.eta.y Physics 2025年第1期9卷 81-100页

作者： Siti Sya.wa.i Na.uha.Ida.wa.i Sa.udin Nurul Sha.a.a.abdul Ha.id a.ma. Fa.ruz Oma. School of Physics Universiti Sains Malaysia11800 USMPulau PinangMalaysia Depa.tment of a.plied Physics Faculty of Science and TechnologyUniversiti Kebangsaan Malaysia43600 UKM BangiSelangorMalaysia Spa.e Science Centre(a.GKa.a. Institute of Climate ChangesUniversiti Kebangsaan Malaysia43600 UKM BangiSelangorMalaysia

Thermospheric neutra. winds(TNWs)refer to the neutra. ga.es in the thermosphere circula.ing a. tides,which pla. a.crucia. role in the dyna.ics of the thermosphere-ionosphere system(TIS).Globa. geospa.e neutra. winds,pa.ticula.ly over the ma.netic equa.or,ha.e been a.subject of study for severa. ***,despite the known importa.ce of neutra. winds,a.comprehensive understa.ding a.d cha.a.teriza.ion of the winds is still *** ground-ba.ed a.d sa.ellite missions ha.e provided va.ua.le informa.ion on the contribution of neutra. winds to the globa. a.mospheric ***,efforts in the globa. monitoring of neutra. winds a.e still la.king,a.d the drivers behind the beha.ior of TNWs a. well a. their influence on the TIS rema.n *** a.dress these knowledge ga.s in the globa. circula.ion of TNWs,it is crucia. to develop a.deep understa.ding of the neutra. wind cha.a.teristics over different *** low-la.itude equa.oria. region in pa.ticula. ha. been observed to exert complex influences on TNWs beca.se of the unique effects of the Ea.th’s ma.netic field a. the dip *** neutra. winds over this region will provide va.ua.le insights into the unique dyna.ics a.d processes tha. occur in this region,thereby enha.cing our understa.ding of their role in the overa.l dyna.ics of the ***,through empirica. observa.ions,a. improved a.ility to a.cura.ely model a.d predict the beha.ior of this region ca. be *** review a.ticle a.dresses cha.lenges in understa.ding equa.oria. winds by reviewing historica. mea.urements,current missions,a.d the intera.tions of ionospheric a.d thermospheric phenomena.empha.izing the need for comprehensive mea.urements to improve globa. a.mospheric dyna.ics a.d wea.her foreca.ting.

关键词： thermospheric neutra. wind thermosphere-ionosphere system dip equa.or equa.oria. region

Systema.ic Geometric Error Modeling for Workspa.e Volumetric Ca.ibra.ion of a.5-a.is Turbine Bla.e Grinding Ma.hine

在线全文

学校读者我要写书评

暂无评论

Chinese Journa. of a.rona.tics 2010年第5期23卷 604-615页

作者： abdul Wa.id khan School of Mecha.ica. Engineering a.d a.toma.ion Beijing University of Aeronautics and Astronautics

a.systema.ic geometric model ha. been presented for ca.ibra.ion of a.newly designed 5-a.is turbine bla.e grinding ma.hine. This ma.hine is designed to serve a.specific purpose to a.ta.n high a.cura.y a.d high efficiency grinding of turbine bla.es by elimina.ing the ha.d grinding process. a.though its topology is RPPPR （P： prisma.ic; R： rota.y）, its design is quite distinct from the competitive ma.hine tools. a. error qua.tifica.ion is the only wa. to investiga.e, ma.nta.n a.d improve its a.cura.y, ca.ibra. tion is recommended for its performa.ce a.sessment a.d a.cepta.ce testing. Systema.ic geometric error modeling technique is implemented a.d 52 position dependent a.d position independent errors a.e identified while considering the ma.hine a. five rigid bodies by elimina.ing the set-up errors of workpiece a.d cutting tool. 39 of them a.e found to ha.e influentia. errors a.d a.e a.commoda.ed for finding the resulta.t effect between the cutting tool a.d the workpiece in workspa.e volume. Rigid body kinema.ics techniques a.d homogenous tra.sforma.ion ma.rices a.e used for error synthesis.

关键词： 5-a.is ma.hine tools ca.ibra.ion modeling geometric errors kinema.ics homogenous tra.sforma.ion ma.rices

Time stepping in discontinuous Ga.erkin method

在线全文

学校读者我要写书评

暂无评论

Journa. of Hydrodyna.ics 2013年第3期25卷 321-329页

作者： La. Wencong khan abdul A Glenn Depa.tment of Civil Engineering Clemson University Clemson S.C. USA

The time discretiza.ion in the Discontinuous Ga.erkin （DG） scheme ha. been tra.itiona.ly ba.ed on the Tota. Va.ia.ion Diminishing （TVD） second-order Runge-Kutta.（RK2） scheme. Computa.iona. efficiency a.d a.cura.y with the Euler Forwa.d （EF） a.d the TVD second-order RK2 time stepping schemes in the DG method a.e investiga.ed in this work. Numerica. tests a.e condu- cted with the sca.a. Burgers equa.ion, 1-D a.d 2-D sha.low wa.er flow equa.ions. The ma.imum Coura.t number or time step size required for sta.ility for the EF scheme a.d RK2 scheme with different slope limiters a.e compa.ed. Numerica. results show tha. the slope limiters a.fect the sta.ility requirement in the DG method. The RK2 scheme is genera.ly more diffusive tha. the EF scheme, a.d the RK2 scheme a.lows la.ger time step sizes. The EF scheme is found to be more efficient a.d a.cura.e tha. the RK2 scheme in the DG method in computa.ion.

关键词： Discontinuous Ga.erkin (DG) method Euler Forwa.d (EF) scheme second-order Runge-Kutta.scheme

Numerica. solution of the Sa.nt-Vena.t equa.ions by a. efficient hybrid finite-volume/finite-difference method

在线全文

学校读者我要写书评

暂无评论

Journa. of Hydrodyna.ics 2018年第2期30卷 189-202页

作者： Wencong La. abdul a.khan Glenn Depa.tment of Civil Engineering Clemson University

a.computa.iona.ly efficient hybrid finite-volume/finite-difference method is proposed for the numerica. solution of Sa.ntVena.t equa.ions in one-dimensiona. open cha.nel flows. The method a.opts a.ma.s-conserva.ive finite volume discretiza.ion for the continuity equa.ion a.d a.semi-implicit finite difference discretiza.ion for the dyna.ic-wa.e momentum equa.ion. The spa.ia. discretiza.ion of the convective flux term in the momentum equa.ion employs a. upwind scheme a.d the wa.er-surfa.e gra.ient term is discretized using three different schemes. The performa.ce of the numerica. method is investiga.ed in terms of efficiency a.d a.cura.y using va.ious exa.ples, including stea.y flow over a.bump, da.-brea. flow over wet a.d dry downstrea. cha.nels, wetting a.d drying in a.pa.a.olic bowl, a.d da.-brea. floods in la.ora.ory physica. models. Numerica. solutions from the hybrid method a.e compa.ed with solutions from a.finite volume method a.ong with a.a.ytic solutions or experimenta. mea.urements. Compa.isons demonstra.es tha. the hybrid method is efficient, a.cura.e, a.d robust in modeling va.ious flow scena.ios, including subcritica., supercritica., a.d tra.scritica. flows. In this method, the QUICK scheme for the surfa.e slope discretiza.ion is more a.cura.e a.d less diffusive tha. the center difference a.d the weighted a.era.e schemes.

关键词： Hybrid numerica. method Sa.nt-Vena.t equa.ions sha.low wa.er flow

Biodiesel synthesis via.meta. oxides a.d meta. chlorides ca.a.ysis from ma.ine a.ga.Mela.otha.nus a.a.husa.nii

在线全文

学校读者我要写书评

暂无评论

Chinese Journa. of Chemica. Engineering 2016年第3期24卷 388-393页

作者： abdul Ma.eed khan Noureen Fa.ima Resea.ch La.ora.ory of Bioenergy Department of ChemistryFederal Urdu University of ArtsSdence and TechnologyCulshan-e-lqbal CampusUniversity RoadKarachi-75300Pakistan

This resea.ch a.ticle demonstra.es the most comprehensive compa.a.ive ca.a.ytic study of different meta. oxides a.d meta. chlorides towa.ds the metha.olysis of triglycerides of ma.ine red ma.roa.ga.Mela.otha.nus a.hqhusa.nii. Ca. wa. found to be the most rea.tive meta. oxide tha. yielded 80% biodiesel while ZnCI2 wa. the most rea.tive meta. chloride tha. produced 60% biodiesel by mecha.ica. stirring for 6 h a. 100-110 ℃. The overa.l rea.tivity order of the ca.a.ysts wa. found to be Ca. 〉 MgO 〉 Pb02 〉 ZnC12 〉 TIC14 〉 PbO 〉 HgC12 〉 ZnO 〉 a.C13 〉 SnCI2 〉 TiO2 wherea., Ca.I2, MgCI2, a.203, HgO, PbCI2, MnO2, MnC12, Fe203 a.d FeCI3 were found to be non-rea.tive for tra.sesterifica.ion of triglycerides. In a.dition, a.deta.led study of the screening of mobile pha.es a.d spra.ing rea.ents wa. conducted which showed tha. petroleum ether ： chloroform ： toluene （7：2：1 ） is the best mobile pha.e, wherea. iodine crysta.s/silica.gel is the best visua.izing a.ent for the thin la.er chroma. togra.hy （TLC） exa.ina.ion ofbiodiesel. Biodiesel production wa. confirmed by compa.a.ive TLC exa.ina.ion. It wa. further supported by the determina.ion of fuel properties of biodiesel, which were found to be simila. to the sta.da.d limits of a.erica. Society for Testing a.d Ma.eria.s （a.TM）,

关键词： Bioma.s Metha.olysis Triglycerides Biodiesel Ca.a.ysts

1-D coupled non-equilibrium sediment tra.sport modeling for unstea.y flows in the discontinuous Ga.erkin fra.ework

在线全文

学校读者我要写书评

暂无评论

Journa. of Hydrodyna.ics 2016年第4期28卷 534-543页

作者： Fa.za. Sa.a.za.eh Ma.EKI abdul a.khan Engineering Depa.tment Massachusetts Maritime Academy Glenn Depa.tment of Civil Engineering Clemson University

a.high-resolution, 1-D numerica. model ha. been developed in the discontinuous Ga.erkin fra.ework to simula.e 1-D flow beha.ior, sediment tra.sport, a.d morphologica. eva.ua.ion under unstea.y flow conditions. The flow a.d sediment concentra.ion va.ia.les a.e computed ba.ed on the one-dimensiona. sha.low wa.er flow equa.ions, while empirica. equa.ions a.e used for entra.nment a.d deposition processes. The sediment tra.sport model includes the bed loa. a.d suspended loa. components. New formula.ions for Ha.ten-La.-va. Leer （HLL） a.d Ha.ten-La.-va. Conta.t （HLLC） a.e presented for sha.low wa.er flow equa.ions tha. include the bed loa. a.d suspended loa. fluxes. The computa.iona. results for the flow a.d morphologica. cha.ges a.ter two da. brea. events a.e compa.ed with the physica. model tests. Results show tha. the modified HLL a.d HLLC formula.ions a.e robust a.d ca. a.cura.ely predict morphologica. cha.ges in highly unstea.y flows.

关键词： da. brea. flow sediment tra.sport modeling Ha.ten-La.-va. Leer (HLL) a.d Ha.ten-La.-va. Conta.t (HLLC) fluxfunctions discontinuous Ga.erkin scheme

Investiga.ion of seconda.y pha.es a.d tensile strength of nitrogen-conta.ning a.loy 718 weldment

在线全文

学校读者我要写书评

暂无评论

Interna.iona. Journa. of Minera.s,Meta.lurgy a.d Ma.eria.s 2020年第9期27卷 1259-1268页

作者： Behrooz Na.a.i Ma.soud Gooda.zi abdul Kha.iq khan School of Meta.lurgy a.d Ma.eria.s Engineering Iran University of Science and TechnologyTehran ***Iran Depa.tment of Mecha.ica. Engineering Manitoba Institute for MaterialsUniversity of ManitobaWinnipeg R3T 2N2Canada

The influence of nitrogen content on the precipita.ion of seconda.y pha.es a.d the tensile strength of a.loy 718 during ga. tungstena.c welding wa. investiga.ed. Va.ious types of precipita.es were cha.a.terized using sca.ning electron microscopy a.d tra.smission electronmicroscopy. The results showed tha. in the fusion zone, the volume fra.tion of Nb-rich pha.es such a. La.es, (Nb,Ti)C, a.d δ pha.es, a. wella. Ti-rich pha.es such a. (Ti,Nb)CN a.d (Ti,Nb)N, increa.ed with increa.e in the nitrogen content due to the microsegrega.ion of Nb a.d Tiwithin interdendritic a.ea.. Nitrogen wa. a.so found to decrea.e the size of γ′′ pa.ticles within γ dendrites. For precipita.es in the pa.tia.lymelted zone, constitutiona. liqua.ion wa. observed for both (Nb,Ti)C a.d (Ti,Nb)N pa.ticles. Ba.ed on the results of tensile tests, the weld conta.ning0.015wt% nitrogen exhibited the highest ultima.e tensile strength (UTS), wherea. more a.dition of nitrogen led to a.decrea.e in both theUTS a.d yield strength due to the increa.ed content of brittle La.es pha.es a.d decrea.ed size of γ′′.

关键词： nitrogen seconda.y pha.es ga. tungsten a.c welding tensile strength a.loy 718