Lecture_5 Contaminants transport processes and transport equations

《Lecture_5 Contaminants transport processes and transport equations》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、MODELINGGROUNDWATERFLOWANDCONTAMINANTTRANSPORTContentof5lectures:1.Introductionandbasicconcepts2.Governingflowequations3.Groundwatermodeling:analyticalsolutions4.Groundwatermodeling:numericalmethods5.TransportprocessesandtransportequationsThefollowingpagesinthisfilear

2、eforLecture5GroundwatermodelingLecture5:transportmodelingChongyuXu1Transportprocessesandtransportmodeling•Sourcesofgroundwaterpollution:Fig6.1ofKinzelbachGroundwatermodelingLecture5:transportmodelingChongyuXu2Transportprocessesandtransportmodeling•Massflux–masstranspo

3、rtedoveraunitsquareperunittimeMassflux=j=c·v(kg/m2s)notethatbothjandvareboldfaces,indicatingvectorsweareinterestedinwhathappensinavolumeofthesediment(orrock),i.e.Thespatialaverageoveravolumej=c⋅vWhichexpresswhathappensonaverageinarepresentativej=nu⋅celementalvolume(RE

4、V)•Requirementsofatransportmodel–Concentrationofdissolvedmass,masspervolumewater,c(kg/m3),and–Porevelocitiesu(m/s),rememberu=v/ne•ne=effectiveporosity,•v=specificflowrates(m/s)(Darcy’svelocity)Darcy’svelocityisrelatedtothetotalcrosssectionalarea.Theporevelocityisrestr

5、actedtotheeffectivecrosssectionalarea.ThereforeitislargerthantheDarcyvelocitybythefactor1/ne.GroundwatermodelingLecture5:transportmodelingChongyuXu3Transportmechanisms•Physicalprocesses–Advection•Carriedalongwiththeaveragevelocityofflowinggroundwater–MolecularDiffusio

6、n:•Movementbyconcentrationgradients(Fick’slaw)fromhighconcentrationareatolowconcentrationarea.–MechanicalDispersion:•mixingthatoccursasthewatercontainingacontaminant(s)flowsaroundthesolidsintheaquifermediaduetoheterogeneityofflowfield.•Chemicalprocesses–Adsorption(ret

7、ardation-makesthepollutionfrontgoesslower)•Adsorptionofpollutentsontothesurfacesofthemineralgrainsintheaquifer–Chemicalandbiochemicalreactions(degradation)•Chemicalandbiologicaldecayandtransformationprocesses•Radioactivedecayincaseofradioactivesubstances(degradation)G

8、roundwatermodelingLecture5:transportmodelingChongyuXu4Schematicdescriptionoftheeffectsofadvection,dispersion,adsorption,andc