简介:足球比赛中人墙是特有的防守手段,全面了解人墙排列和跳起移动的’变化规律,对进一步提高任意球防守的认识水平,有一定的实践和理论意义。运用文献法、访谈法和录像统计等方法,对南非世界杯和2010—2011欧洲冠军杯共118场比赛中前场任意球防守人墙排列的形式和特征进行了统计分析。应用测量法对人墙跳起移动的规律进行了探讨。结果表明:人墙排列的人数在2—6人之间,排列人墙的人数与罚球地点与球门的距离和射门角度有关,距离越近,角度越大排列的人数越多;防守人墙采用起跳防守的次数多于原地不动防守;人墙的组合形式多种多样,其中“山”字形人墙组合最多;人墙跳起的高度与罚球距离的关系图呈“钟”形。
简介:Severalindustrialapplicationssuchaselectronicdevices,heatexchangers,gasturbineblades,etc.needcoolingprocesses.Theinternalcoolingtechniqueisproperforsomeapplications.Inthepresentwork,computationalsimulationsweremadeusingANSYSCFXtopredicttheimprovementsofinternalheattransferintherectangularribbedchannelusingdifferentcoolants.Severalcoolantssuchasair,steam,air/mistandsteam/mistwereinvestigated.Theshearstresstransportmodel(SST)isselectedbycomparingthestandardk-ωandOmegaReynoldsStress(ωRS)turbulencemodelswithexperimentalresults.Theresultsindicatethattheheattransfercoefficientsareenhancedintheribbedchannelwhileinjectingsmallamountsofmist.Theheattransfercoefficientsofair/mist,steamandsteam/mistincreaseby12.5%,49.5%and107%overthatofair,respectively.Furthermore,incomparisontoair,theair/mistheattransfercoefficientenhancesbyabout1.05to1.14timeswhenthemistmassfractionincreasesfrom2%to8%,respectively.Thesteam/mistheattransfercoefficientincreasesbyabout1.12to1.27timeshigherthanthatofsteamovertheconsideredrangeofmistmassfraction.