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ID:23225092
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页数:14页
时间:2018-11-05
《[财会考试]附加讲义》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、【飛機動力學】附加講義Longitudinalresponsestoatmosphericgusts113LongitudinalresponsestoatmosphericgustsI.Preliminaryremarks○Wearegoingtodealwiththeappearanceofatmosphericgusts⇨Thetwocomponentsofthegustisoftenreferredtoashorizontalgustandtheverticalgust.○Whatwill
2、theatmosphericgustsdototheaircraftmotion?113II.Re-derivethelongitudinalequations○Theproblemcanberesolvedbyre-derivingtheequationsofmotion.○Let¢sgobacktothepre-treatedlongitudinalequationsonp.33:○Tolinearizethisequationset,wehadintroducedtheperturbatio
3、ns---Amongtheseperturbations,andrepresentthechangesinrelativewindduetochangeinaircraftflightspeed.○Withthepresenceofthegusts,thefollowingmodificationtotheperturbationsofandwillbenecessary:and.---Minussignsreflecttthatgustwindchangestherelativewind,whi
4、chisofoppositesignoftheflightspeed.⇨Thesechangesintheperturbationsofandwillnecessitatepropermodificationstotheaerodynamictermsofthelinearizedequations.⇨Thegravitationaltermsandtheinertialtermsoftheequations,however,willnotbeaffectedbythepresenceofatmo
5、sphericgusts.113○Linearizationoftheequationsetunderthepresenceofgusts:lForthedragequation:1.Expansionofandthatincludesthegustterms:.and---ThelasttermontheRHSreflectsthatverticalgustslantstherelativewind,hencetheliftvector,causinganadditionaldragforcet
6、oappear.---Wehavealsoassumethatandsothat.2.Theresultingthedragequation..⇨GusteffectappearsastwoadditionaltermsontheRHS.⇨Theseadditionaltermsactasinputstothelongitudinaldynamics.113lFortheliftequation:1.Expansionofthatincludesthegustterms:.2.Theresulti
7、ngliftequation:lForthepitchingmomentequation:1.Inpreviousnote,wehadexpandedintoasfollows:.2.Here,thefollowingmodificationswillbemade:3.Thefollowingphenomenonabouttheverticalgusthasalsobeenobserved:113·isaresultof:·Insuchaverticalgust,thetailfeelsanadd
8、itional(w.r.t.thewing)---Pointingupward.·Anadditionalchangeinwillresult:·Thischangeinresultsinthefollowingchangeinpitchingmoment:(Because)4.Thefinalpitchingmomentequation:⇨NotethatatotaloffourgusttermsappearintheRHS.113【Modifiedlongitudinalequ
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