ForcesThatEnableFlight的力量使飞行

ForcesThatEnableFlight的力量使飞行第1页/共44页SourcesofLiftDynamicpressureaboveairfoilhigherthanbelow,thusstaticpressurebelowgreater,pushesairfoilupSomeairdeflecteddownwardfromlowersurface,opposite(upward)reactionforceisanothersourceoflift第2页/共44页第3页/共44页第4页/共44页AirfoilsWingBoneatleadingedgewithfeatherstrailingcreatesconvexshapeForearmwithsecondariesattachedisthemainsourceofliftPrimaryfeathersAsymmetricshapewithstiffrachisleadingandlongbarbstrailingcreatesconvexshape第5页/共44页第6页/共44页第7页/共44页ThrustProducedlikepropellerLeadingedgeofwingcutsvertically,forceproducedisforwardthrustLargebirdstwistprimaryfeathersaswingbeatstoproducethrust,forearmstayshorizontalandcontinuestoproduce(increased)liftSmallbirdscreatethrustwithentirewing,plusadditionalthrustfromprimaryfeathersPassiverecoveryupstroke第8页/共44页第9页/共44页FlightAdaptationsRigidwingandfeatherstructureRequiredtocreateairflowpatternsthatresultinliftBecausewingformmaintained,forcescreatedresultinliftratherthanbendingofbodyLightweightWeightcounterslift第10页/共44页ApplicationofThrustMomentum(massxvelocity)perpetuatesthrustDragcountersthrustProfiledrag(frictionwithair,thereasonforstreamlining)Induceddrag(turbulence)第11页/共44页第12页/共44页SourcesofDragAirflowoverwing(induced)Wingtips(induced)Projectionsfrombody(profile)AdaptationsinforelimbeliminatesourcesofprofiledragAlulaistheexception第13页/共44页第14页/共44页FeaturesusedtomaintainliftProblemwhenwingisheldatsteepangleAluladeflectsairdownoverwingtomaintainflow,preventinduceddragSlotsinwingsperformsamefunction,frontprimarydirectsairoverprimarybehindAirforcedthroughslotsexpandsonuppersurface(reducedstaticpressure)tocreatemorelift第15页/共44页第16页/共44页StaticSoaringUsethermals,obstructioncurrentstoattainaltitudeUsegravitytogeneratespeed,liftLowwingloading(largewingsrelativetoweight)promotesuseofliftMustbeabletomaneuveratslowspeedsUsealula,haveslotsinwingsBroad,roundedwingsproducedragtoreducemomentum第17页/共44页第18页/共44页第19页/共44页SoaringbySmallBirdsOnlypossibleathighspeeds,becausespeedistheonlysourceofmomentumGeneratespeedwiththrust,usespeedtogenerateliftLowwingloadingtopromoteuseofliftLong,narrow,pointedwingstoreducedrag,maintainmomentum第20页/共44页第21页/共44页第22页/共44页DynamicSoaringUsegradientinwindspeedatsurfaceoceanUsewind,gravitytoincreasespeed,gainmomentumasglidedownwindUsemomentum,windtogeneratelift,gainheightwhenturnintowindGainvelocityasriseduetowindspeedgradient,startcycleoveragain第23页/共44页FormforDynamicSoaringDynamicsoaringisbasedonperpetuatingmomentumHighwingloadingincreasesmomentumLong,narrow,pointedwingstoreducedrag,maintainmomentum第24页/共44页第25页/共44页第26页/共44页WingFormLongerhandportioninspeciesthatrelymoreonthrustcomparedtosoaringbirdsHighspeedfliershavelong,narrow,pointedwings(falcons)Manybirdshaveshorter,moreroundedwingsformaneuverabilitythroughcover第27页/共44页第28页/共44页WingLoadingLowinsoaringbirds(exceptdynamicsoarers),highindivingbirdsHigherinlargerbirdsduetovolume(weight)–area(wingsize)relationshipWingshapedoesnotchangewithsizeMigrationselectsforlonger,narrower,morepointedwings第29页/共44页第30页/共44页第31页/共44页第32页/共44页第33页/共44页TailsUsedasbrakeandrudderLongertailsgeneratemoredragLong,forkedtailbestforhigh-speedmaneuvering,shorttailbestforhighspeedAlsomaneuverbyfoldingwingsTailssometimesaredisplayfeatures第34页/共44页第35页/共44页第36页/共44页LandingSlowdownbybrakingwithtail,feet(webbedespecially)Increaseangleofwings,twistwingstoreduceforwardcomponentofthrustTurnintothewind,comeinbelowperchSomelargebirdshavedifficultylanding(toomuchmomentum)第37页/共44页第38页/共44页Take-offUsegravitytogeneratespeedforliftbyjumpingfromperchorcliffUsewindandspeedtogenerateliftbyrunningintowindDynamicsoarershavebiggestproblemUsethrustbyrotatingwingsverticallyShort,broadwing=powertake-offwing(withwhitemuscle)第39页/共44页第40页/共44页第41页/共44页Hummingbirds:AvianHelicoptersFlytotallybythrustWingismostlyhand,littleforearmRotatewing180degreesto