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时间:2020-05-09
《超声空化及絮体破碎过程的模拟与试验分析.pdf》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、中国环境科学2015,35(5):1429-1435ChinaEnvironmentalScience超声空化及絮体破碎过程的模拟与试验分析郭璇,杨艳玲,李星,周志伟,马长红,张洋(北京工业大学,北京市水质科学与水环境恢复工程重点实验室,北京100124)摘要:为探究利于空化效应的超声条件及超声波破碎絮体机理,基于Matlab平台建立空化气泡模型及2种简化的有限扩散聚集(DLA)絮体破碎模型,进行计算机仿真,并通过试验分析得到实际絮体破碎模式.结果表明:随着超声频率的增加,空化效应减弱;声能密度的增加导致空化气泡振幅增大,声能密度为7W/mL时气泡振幅可达初始半径的200
2、倍,空化效果较好.低声能密(O.O3~3W/mL)和低超声频率(25--40kHz)处理絮体时,剥蚀作用为主导作用,超声后絮体粒径减小,分形维数增大;声能密度超过3W/mL或频率大于40kHz,大规模破碎占主导作用,实际絮体粒径减幅小且结构散.40kHz的超声频率更利于絮体的破碎,作用10min后,絮体粒径减幅达9.8%,分形维数为1.394,结构更加密实.关键词:超声;空化效应;数值模拟;有限扩散聚集:絮体破碎中图分类号:X703,TU991.2文献标识码:A文章编号:1000—6923(2015)05-1429—07SimulationofuRrasoundcavit
3、ationbubb~andnumerical/experimentalanalysisofllocsbreakageprocess.GUOXuan,YANGYan-ling。,LIXing,ZHOUZhi-wei,MAChang-hong,ZHANGYang(CollegeofArchitectureandCivilEngineering,BeijingUniversivyofTechnology,Beijing100124,China).ChinaEnvironmentalScience,2015,35(5):1429-1435Abstract:Inordertoexp
4、lorethesonicationconditionfortheidealcavitationefectandtofindoutthebreakagemechanismoffloesexposedtoultrasound,amodelofcavitationalbubbleandtwosortsofsimplifiedmodelsofdiffusion-limitedaggregation(DLA)flocbreakagewereestablishedandsimulatedbasedonMatlab.Thepracticalfloesbreakagepatternswe
5、reverifiedthroughexperimentalanalysis.Theresultsindicatedthatthecavitationefectdecreasedastheultrasonicfrequencyincreased.Theincreaseofultrasonicdensityledtotheincrescentamplitudeofcavitationbubble,whenthesonicationdensitywas7W/mL,theradiusofcavitationbubblesCanbeenlargedto200timeslongera
6、ndthecavitationefectwasfairlygood.Whenthefloesweretreatedatlowenergydensity(0.03-3W/mL)andlowfrequency(25-40kHz)ultrasonication,surfaceerosiondominatedthebreakageefect,whichwasreflectedbydecreasedradiusandincreasedfractaldimensionofflocs.Whentheenergydensityexceeds3W/mLorthefrequencysurpa
7、sses40kHz,thelargescalefragmentationwasthemainmechanism,leadingtothesmallerfloessizeandlooserstructures.Thesonicationofthefrequencyof40kHzismorebeneficialtofiocsbreakage,withtheexperimentalresultthat10minutes’ultrasonicationCanleadtoadinimutioinrateof9.8%oftheradius
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