简介：在当今知识经济时代,水土保持科学技术有了重大突破:一是随着朱镕基总理"十六字"方针的贯彻和禁伐令的执行,扼制了毁林毁草开荒,推行放牧改舍饲,促使由广种薄收向少种高产转变,在农业耕作制度上开展了一场新的革命;二是坚持草灌乔结合,草灌先行,在林种布局、营林技术、新品种推广上有重大进步;三是基本农田建设技术和高产稳产技术有了重大突破;四是修路开矿建厂等基本建设中注意环保,强化了水土保持治理;五是运用新技术、新手段、加强了水土保持科技监测与技术管理.

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简介：Thispaperisconcernedwiththewavesgeneratedbya3-Dbodyadvancingbeneaththefreesurfacewithconstantspeedinatwo-layerfluidoffinitedepth.ByapplyingGreen'stheorem,alayeredintegralequationsystembasedontheRankinesourcefortheperturbedvelocitypotentialgeneratedbythemovingbodywasderivedwiththepotentialflowtheory.Afour-nodeisoparametricelementmethodwasusedtotreatwiththesolutionofthelayeredintegralequationsystem.Thesurfaceandinterfacewavesgeneratedbyamovingballwerecalculatednumerically.Theresultswerecomparedwiththeanalyticalresultsforamovingsourcewithconstantvelocity.

简介：Twonear-fieldmethods,namelytheintegralmethodanddifferentialmethod,werepresentedforgivingsecond-ordermeandriftforcesandmomentsbetweentwofixedsubmergedbodiesinregularwaves.Fortheintegralmethod,withaseriesofmathematicalmanipulations,second-orderdriftforcesandmomentscouldbeeasilyexpressedbydistributedsourceswhichcouldbecalculatedbysourcedistributiontechniqueswiththeassumptionthattheamplitudeofshipmotionsaresmallonthebasisofthelinear3Dfrequencytheory.Forthedifferentialmethod,driftforcesandmomentscouldbeexpressedbythederivativeofvelocitypotentialwithrespecttospacecoordinate.Becausetwobodieswouldbehaveasasinglebodywhiletheclearanceisverylarge,thenumericalresultsofonesphereinsuchcaseweregivenandcomparedwithanalyticalresultsofasinglespherewhichdoesnotinvolvetheeffectoffreesurface.Whensubmergeddepthbecomesenoughlarge,agoodagreementcanbereached.Thentheintegralmethodwasusedtopredictthesecond-orderdriftforcesandmomentsoftwosubmergedspheresandspheroidswithasmalllateralseparationdistanceinwavescomparedwiththenumericalresultsobtainedbythedifferentialmethodandtheyagreewell.Bycomparison,itindicatestheinteractioneffectsbetweentwosubmergedbodieshaveaprofoundinfluenceonthedriftforcesandmoments.Inthispaper,theforwardspeedeffectonsubmergedsphereswasalsoconsidered.

简介：为了保证矿山安全高效开采,通过分析影响采场稳定性关键因素及破坏机理,应用数值模拟法对二步矿柱在不同结构参数和两侧不同充填配比开采条件的稳定性进行分析,优选出安全高效的一步采场充填配比和二步采场的结构参数。采用FLAC3D数值模拟,计算和分析在开采过程中,不同结构参数和两侧不同充填配比的采场顶板的应力、应力分布区域面积及位移变化特征,得出各不同方案的采场顶板稳定情况。结果表明：采场受两侧充填体配比的影响较为明显,一步采场灰砂比由1∶6改变到1∶8时,对二步采场的稳定性影响较小;灰砂比小于1∶8和采场宽度大于18m时,采场顶板的拉应力和位移的变化率逐渐变大,采场的稳定性迅速降低。因此,综合矿山生产安全、高效及成本考虑,建议一步采场充填配比为1∶8、二步采场的宽度为18m。

简介：Inthispaper,perturbationmethodandFourier-cosine-expansionmethodareusedtosolvea3-DnonlinearproblemofasupercavitatingflowinaninclinedfieldofgravityatlargeFroudenumbers.Byexpandingthevelocitypotentialintoapowerseriesofasmallparameter,theoriginal3-Dnonlinearproblemisreducedtoanumberof2-Dones.Thesolutionsofthefirstthreeordersarederivedindetailandexpressedintermsofthecompleteellipticintegralsofthefirstandsecondkinds.Thentheboundaryintegralequationmethodisappliedtogetthenumericalsolutionsforeachorder.Computationalresultsareprovidedforsupercavitatingflowspastconesundervariousflowconditions.

简介：Inthepresenceofbottomwater,adropinthereservoirpressureduetofluidproductioncausestheaquiferwatertoexpandandtoflowintothereservoir.Therefore,hydrocarbonproductionfromawellislimitedbythecriticalflowrate.Themainpurposeofthisstudyistoinvestigatethebreakthroughtimeandthecriticalratebyusinganovel3-Dhorizontalwellmodel.Basedonthehypothesisthatthehorizontalwellislocatedinanypositionofacircularreservoirwithno-flowboundaryonthetopofthereservoirandconstantpressureboundaryatthebottom,thehorizontalwellhasbeenregardedasaninfiniteconductivitylinesinkandthena3-Dsteady-stateflowmodelofthehorizontalwellissetup.ApointsinkpressuresolutioncanbeobtainedwiththeFouriertransform.Theresultofthepressuredistributionoftheuniformfluxhorizontalwellcanbepresentedbymeansoftheprincipleofsuperposition.Accordingtothestablewatercrestingtheory,thisstudyconfirmsthestableheightofwatercrestingandthecriticalrate.Meanwhile,itcanre-confirmthebreakthroughtimeataspecificrate.Theoutputofacomparisonbetweenthis3-Dmodelandthereservoirnumericalsimulator(Eclipse)showsthemethodpresentedherecanbeappliedtoinvestigatethebehaviorofawatercrestingandtopredictthebreakthroughtimeatthebottomwaterdriverreservoir.

简介：Inthisarticle,theanaglyphvideomakerisemployedforgeneratingrealistic3-DflowsandthesoftwareFlowAnimatorisdevelopedusingthattechnology.BasedonMicrosoftWindowsPresentationFoundation(WPF),thereal3-Dsceneissetupandmarkerparticlesaredistributedinitrandomlyinordertocreateamorenaturalflowscenario.ThetrajectoryoftheparticlemotioniscalculatedwithLagrangiandescriptionin3-Dspace.Duringthesimulation,theviewportcanbechangedinordertofocusondifferentpartsofthemodelbypanning,zooming,rotatingandinclinationvariationetc.Markerparticlesmayappearindifferentshapes:spheres,tracking-balls,cylindersandribbonsinordertofitdifferentflows.Itisthefirsttimethatthevideoanaglyphtechnologyisemployedinthe3-Dhydrodynamicsimulation,whichremovestheobstaclesfor3-Dscenestoberenderedonaflat-paneldisplay.

简介：Ageneralizedbendflowmodel,treatinga90°singlebendand60°continuousbends,wasdesignedtoquantitativelydescribe3-Dturbulencemechanismofcirculatingnot-fully-developedflowinopenchannelswithbends.The3-Dfluctuatingvelocitiesofturbulentflowweremeasuredandanalyzedwitha3-Dacoustic-Dopplervelocimeter.Formulafor3-Dturbulentintensitywasderivedusingthedimensionanalysisapproach.Expressionsofverticalturbulent-intensitydistributionswereobtainedwiththemultivariant-regressiontheory,whichagreewithexperimentdata.Distributionsofturbulentintensityandturbulentstresswerecharacterized,andtheirrelationshipswereconcluded.Inthebend-turbulent-flowcoreregion,longitudinalandlateralturbulent-intensitydistributionsarecoincidentwithlineardistribution,butinnear-wallregionarecoincidentwiththeGammadistribution.VerticalturbulentintensitydistributionsarecoincidentwiththeRayleighdistribution.Herein,itisconcludedthatthebendturbulenceisanisotropic.

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简介：A3-Dtimedomainmethodisdevelopedtoinvestigatethegapinfluenceonthewaveforcesfor3-Dmultiplefloatingstructures.Specialhydrodynamicresonanceduetosmallgapsbetweenmultiplefloatingstructuresonwaveforcesisexamined.Strongandcomplicatehydrodynamicinteractionsbetweenthefloatingbodiesareobservedandthenumericalcomputationshaveprovedtheexistenceofthesharppeakforceresponseoneachfloatingbodyatsomespecialresonantwavenumbers.Bycomparisonwiththeresultsfromthefrequencydomaintechnique,theresultsobtainedfromthetimedomainmethodrevealthesimilarresonantphenomenaandhydrodynamicinteraction.TheresonantwavenumbersarealsoprovedaroundkL=nπ(n=1,2,…,∞)withacorrespondingfrequencyshift.Thestronghydrodynamicinteractionfeatureispracticallysignificantforthedesignofmodulestructuresandthelinks(connection)inwholethefloatingbodysystem.

简介：Three-dimensionalseepageindoublefracturedmediawasmodeledinthispaper.Thedeterminationofhydraulicconductivitytensorofrockmassisavitalproblemfortheseawaterintrusionorseawaterencroachmentandseepageoffissuredmedium.Accordingtothegeologicalandhydrogeologicalconditionsforthe2nd-stageconstructionoftheThreeGorgesProject(TGP),thephysicalandmathematicalmodelsforthegroundwatermovementthroughthe3Ddoublefracturedmediaofrockmassduringconstructionwereestablishedinthispaper.Basedondiscontinuity-controlinversetheory,somerelatedparametersofdoublefracturedmediawereinversedwithfluxbeingtheknownquantityandcalibrationofwatertabletheobjectivefunction.Synchronously,theseepagefieldoftheconstructionregionwassystematicallyanalyzedandsimulated,theresultsofwhichexhibitthatthedoublefracturedmediamodeloffracturewatercancomprehensivelyandcorrectlydescribethegeologicalandhydrogeologicalconditionsintheconstructionregion.

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简介：Axisymmetricliquidjetshavebeenstudiedextensivelyformorethanonecentury,whilenon-axisymmetricjetsarealsoverycommoninengineeringapplicationsbutattractlessconcern.BasedonEulerianfluid-fluidmodelinFluentsoftware,thisarticleanalysizesthe3-DflowfieldsofpressureatomizerswithV-shapedcutatorifice,whichwillresultinanon-axisymmetricliquidjet.Flowrateanalysisandjetstructureanalysisarecarriedout,theresultsshowthattheflowratecanbeformulatedbyaddingacorrectioncoefficienttotheformulaofinviscidaxisymmetricjetsinatomizationregime,whentheWebernumberislowenoughtomaketheflowfalloutofatomizationregime,andthejetstructuretogetherwiththeflowrateformulawillchange.Analysisshowsthattheevolutionofthesprayandthereforethestructureoftheliquidjetareaffectedmuchbyrelativevelocityandthelocalvolumefractionofliquidphase.

简介：A3-DnumericalformulationisproposedonthehorizontalCartesian,verticalsigma-coordinategridformodelingnon-hydrostaticpressurefree-surfaceflows.Thepressuredecompositiontechniqueandθsemi-implicitmethodareused,withthesolutionprocedurebeingsplitintotwosteps.First,withtheimplicitpartsofnon-hydrostaticpressuresexcluded,theprovisionalvelocityfieldandfreesurfaceareobtainedbysolvinga2-DPoissonequation.Second,thetheoryofthedifferentialoperatorisemployedtoderivethe3-DPoissonequationfornon-hydrostaticpressures,whichissolvedtoobtainthenon-hydrostaticpressuresandtoupdatetheprovisionalvelocityfield.Whenthenon-orthogonalsigma-coordinatetransformationisintroduced,additionaltermscomeintobeing,resultingina15-diagonal,diagonallydominantbutunsymmetriclinearsysteminthe3-DPoissonequationfornon-hydrostaticpressures.TheBiconjugateGradientStabilized(BiCGstab)methodisusedtosolvetheresulting3-Dunsymmetriclinearsysteminsteadoftheconjugategradientmethod,whichcanonlybeusedforsymmetric,positive-definitelinearsystems.Threetestcasesareusedforvalidations.Thesuccessfulsimulationsofthesmall-amplitudewave,asupercriticalflowoverarampandaturbulentflowintheopenchannelindicatethatthenewmodelcansimulatewellnon-hydrostaticflows,supercriticalflowsandturbulentflows.

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简介：　　新世纪的篇章刚刚翻过一页,又奉献给水利工作者一件丰厚的礼物--更名为.……

简介：我刊已加入科技部'OSID计划'(OpenScienceIdentity开放科学计划),该计划通过在期刊每篇文章上添加OSID开放科学(资源服务)标识码,为读者提供增值服务。作者需要将本文的1分钟语音介绍及开放的科学内容与数据等补充材料上传到OSID码中。有利于科研成果交流传播,提升期刊创新能力,扩大论文与期刊的影响力,建立学术评价标准。

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简介：在水资源严重短缺的华北地区，水已成为经济发展的最大制约因素。从发展的眼光看，分析研究水利发展形势，为实现我国经济又快又好地发展提供水利保障，必须寄望于民生水利。该文从推进民生水利建设出发，提出了民生水利建设主导思想。从群众最关心最受益的问题阐述了几点看法和见解。