简介:Anumericalsimulationisperformedtofindoutakeyvorticalstructureinthelaminar-turbulenttransition.Alow-speedstreakisgeneratedinsidealaminarboundarylayerusinganisolatedcuboidroughness,aimedatprovidinganenvironmentunstabletoouterdisturbances.Then,ashortdurationjetisissuedintotheboundarylayer.Whenthejetvelocityislow,somevorticesappearintheboundarylayer,butthetransitionoftheboundarylayerdoesnottakeplace.However,whenthejetvelocityexceedsacertainthreshold,twovorticesnewlyappearabovetheelongatedlegsofaV-shapedvortexandonlyoneofthemisstretchedandsurvives.Afterthat,vorticesaregeneratedoneafteranotheraroundthesurvivedone.Bycomparingthedecayedandthesurvivedvortices,itisfoundthatthedifferenceintheirheightsisthekeycharacteristicwhichleadstothetransition.
简介:摘要当前青少年生活自理能力差、心理承受能力差、生活适应能力差,这些特点要求学校教育应从根本上转变教育观念,发挥社会、家庭、学校的作用。
简介:摘要本文围绕初中语文拓展性教学课题展开了研究谈论,并提出了加强初中语文拓展性教学的具体对策,以期为广大初中语文教学工作者提供一定的参考。