民航机务英语教程【完整版】(文档可以直接使用，也可根据实际需要修订后使用,可编辑放心下载）LessonOneBernouIli’sPrincipleWhyPlanesFlyAviationisdependentupontheprinciplediscoveredbyaneighteenthcenturyscientist，DanielBernoulli.①Bernoulli’sprinciplehelpstoexplainwhyanairplaneflies，howawingproduceslift，andhowfuelflowsinanaircraftcarburetor．Itexplainstherelationshipbetweenthepressure，thevo1umeandthevelocityofafluidinmotion．Simplystated，thevelocityofagivenvolumeofafluidinmotionisinverselyproportionaltoitspressure.Asvelocityincreases，pressuredecreases．Sincebothgasesandliquidsareclassifiedasfluids．We’lluseairtodemonstratethepropertiesofafluidinmotion．ThereareseveralsimpleexperimentsthatdemonstrateBernoulli’sprinciple．Thesimplestmaybeconductedwithonlyasheetofpaper．②Holdthepaperuptoyourlipsfindblowacrossthetopsurface．Noticethatthepaperrises．Thevelocityoftheairoverthetopofthepaperisgreaterthanthatunderthepaper．Alowpressureareaiscreatedabovethepaperandthedifferenceinpressurecausesthepapertorise．Perhapsyouwalkpastthevacuumcleanerdepartmentofdepartmentstoreandyou’llseeaping—pongballsuspendedintheairabovevacuumcleanerseeminglywithoutsport．Theairpassingaroundthecurvedsurfaceoftheballistravelingfasterthantheairjustbeonthesurface．③Again,thehigherpressureoutsidetheairflowcausestheballtoremaininthecenteroftheairflow．Anothersimpleexperimentusesapieceofpaper,astraightpinandasimplesewingspoo1．First，pushthepinthroughthepaperandinsertitintheholeinthespool，thepinsimplykeepthepaperfromdroppingtothefloor.Now,blowthroughtheotherendofthespool,alowpressureareaiscreatedasthevelocityoftheairincreasesbetweenthespoolandpaper．Thehigheratmosphericpressureonthebackofthepaperholdsthepaperclosetotheendofthespool．Theseexperimentsillustratethefactthatwhenthevelocityofthefluidincreases,thepressuredecreases．Conversely,whenthevelocitydecreases,thepressureIncreasesHowdoesthisapplytoaviation?Let'splacearestrictioninthepathofmovingairinthiswindtunnel．Smokeinjectedintotheairstreamindicatesthepaththeairtakesaroundandthroughtherestriction．Therestrictionis