Twenty-Third Symposium on Naval Hydrodynamics (2001) / Chapter Skim
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Pressure Fluctuation on Finite Flat Plate Above Wing in Sinusoidal Gust
Pressure Fluctuation on Finite Flat Plate Above Wing in Sinusoidal Gust
Pages 330-341
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From page 330... ...
ABSTRACT It is generals said that the amplitude of pressure tract ation induced by a sphere varying ow volume wish time is propo tional to file second derivative of the volume variation Pressme fluctuation induced by a c witatmg wing is a similar es srnpl e b 6 is panel as a modeled cavitation phenomenon, we treat the pressme flu tuation on a unite flat plate Educed by a wing advmcing m unifo m flow with a sinusoidal gust md varymg its Ihmt new wish time The wing is represented by a simple smface pmel method " SQCM" which c m h eat the unsteady motion b calculation for a Unite flat plate, we use four kin d. of calculation methods: file btw one uses a min or image method, file second one does the solid boundary factor medhod, the fLi d one does file source dish ibution method md the last one does QCM Comparing these four kinds of results for 2-D md 3-D cases, we discuss file availability of the fom methods md inw tigate the relation between the amplitude of messme fluctuation md the second derivative of file wing volume 1.
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From page 331... ...
vRetdex Mirror Image ~ v 9=~— d _ d _~_~,~ _ At) Fig I Coordin se Sy hem md Schem tic Diagram for Wing md Fl t Pi he calcul Lion methods to repn sent file Unite fl t pi he The hut one is the minor image medhod md the second one is file solid boundary factor medhod, which me Us to multiply the pressure induced by the unsteady monowing by the factor 2.0 The third one is the source dishibution medhod (SDM)
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From page 332... ...
for QCM mdnmmbff of so :~e pmek is 10 pff ch d leng h c for SDM 3.1 Prff sure Buetu ~d~m due to wing k' n gm~t Fg 2 hows6hemiataeousp~ edEshbubon(tme tep 2S0) cmcak~d by QCM a d SDM on dhe fla plae of tw length 5c md lOc md Fig 3 show vo tex dEshibution y ~ adso:~edEs~ibubon ffr adhesametime tep Fmm Fig 2 we fmd dh t QCM giws nealy dhe same messure dishibution for lp=5c, lOc, while SDM d es dffe~ent dEshibutions for two kmds of 1~ dhough ffr is nealysame y~ dEshbutionofQCM how ali61edfffffft dEshbutions betwff 5c md lOc, but y~ saishes dhe mm teady Kuba condbtion m ffkEtion to 6he solid b mday condbtion a d how a kile nse nea dhe leadi g edge ff a usual thm wmg Fig 4 how a c mpaison of,messure dEshibutionsobtamedfor 1~ = 5c at time teps245,2S0 by QCM ad SDM ad Fig 5 hows dhe cone pondmg y~ a d ffr dishibutions From 6hese Fig es, we notice dh t QCM results give more stale ad reffonmie pressme dEs~ibubons dha SDM results eva~ if ffr hows smodhff dEs~ibubon Thi seffms to be d e k dhe slable flowprod ced by6heunsb dyKutacondbtion Fig 6 howsac mpaisonof amplit de of ,mess :e fluctuaion AC~ betw ff QCM md SDM We hnd QCM md SDM giw fairly different dEshibutions of AC~ excffpt dhe cfftrd pat Epecimiy SDM gi es lager AC~ dh m QCM m dhe fore pat a d does loWff AC~ mflff6hecentffpat6hmQCM,addhff giws k~rge AC~ nem dhe t aLmg edge F m 6hese results, we dEmk dhff QCM giws more tale ad remitic pressure fluctuffion f or 2-D m b Iffm 6h m SDM Fig 7 a d Fig S h w 6he contribubons of dhe mm teffiy componfft i ¢/it a d 6he wlocity componfft to dhe kffm ACp mcffe of QCM ad SDM, re pe tiw k We mm t notice dhff dhese c :ves ae not ffkEtiw si cc effh ,mess :e fluctuffion hff phffe dffffff cc F m dhese Figmres, we mmdfftad 6hm QCM giws more ~effona le beha iornem dhe ieffmg edge of dhe fff piffe 6ha
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From page 333... ...
. -2 0 2 Xk Fig 7 Component of mplit de of Pressure Fluct ation on flat Plate
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From page 334... ...
~\ i5 . O ,~- O ~ ~ +QCM ~1 ~ n Mirror image -0 2 +QCM ~ Cp n M rror mage n 2Cp Time Step 280 - Time Step 280 04 -2 0 2 xk O xk 1 Fig 9 Pressure Di tribution on Fiat Plate Fig 12 Comparison of Pressm e D ish ibution of 2-D Wing C ~ - T 7 ' P +QCM CL .
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From page 335... ...
~ Fig 13 Effects of Phase Ddffer:me y on mplitude of Pressme Fluctu tion _~ ~ +~=00 $=7r 2 :~ : -2 0 2 x/c Fig 19EffectsofPhaseDifference y on mDhtude of Pressure Fluctu tion
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From page 336... ...
ondheflaplaeatmesbpl48 mdFig 22d es 8he,mess:e dEshbutions ondhemid h d kme (:s=0.5c) a 8he same time tep These dEshbubons seem k be pla sible a mmd dhe fore ad wmg pats Though SDM giws s me edge effect to C~, but degree of the effect is not k~rge c mpacd winh 2-D ca e Figs 23 a d 24 how a c mpaimn of C~ obtained by the four methods m both :s,y due tions it is mtffe mg to notice dhff 8he fom medhod giw imik~r dEshbutions ~Cffpt dhe mfl pat md SDM ca giw ~effona le C~ a ow dhe wmg We dEmk dhff dhis may be d e to dhe wemkff edge effe t c mpacd winh 2-D fl t piffe We h w a compaimn of dhe ampEt de dishibution of dhe ,mess :e fl et aion AC~ mFig 25 a dFig 26 A mmddhe wmg pat, ffl medhod giw nemiy dhe same wffues, but d dfffffft tffdffcies m dhe mfl pat ff dhe 2-D cffe Fig 27 hows dhe niffions betw en AC~ a d k~ m cffe of dhe 8hickness-wnymg wmg We fmd agam Imeaity betw ff dhffm i dhe n~nge of k~=1.0~3.0 Thff we h w i Fg 28 a c mpaimn of dhe ~kd b mday ffftom ff dhe Cff tff of dhe plae obtamed by QCM a d dhe min imffge medhod a d fmmiy mFig 29 ac mpaison of dhe phffe dffffff cc effe ts
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From page 337... ...
-2 0 2 yk Fig 24 Pressure Dish ibution on Flat Plate y=OO + QCM ~ SDM -2 0 2 xk Fig 25 Amplitude of Pressure Fluctuation on Flat Plate
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From page 338... ...
CONCLUSION '\ +QCM ~ n Mirror image ~ \ X=0 5C y=OO 1 2 3 dk 4 Fig 23 Compa ison of Solid Bounda y Factor We appbed QCM SDM, fLe mimn image medhod md 6he solid bommday faclor medhod t fLe m blem of mplit de of,messure fluctuation mduced on 6he fmite flat pLte set a ow a wmg i mmif m flow wif h a smusoidm gm t F m fLe obt med results, we conchde ff follows . 7he mimn image medhod fLe solid bommday factor medhod, QCM giw nealy 6he s me mplit de of ,mess :e fluctu dion on a finite flat plate m fLe upshe m md Uppff regions of 6he wmg i 2-D a d 3-D problem SDM is simiLar only m 3-D m blem .
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From page 339... ...
5g mp 221-234, 1979 T Ho hi o, "E timatipp of Unsbady Cavitatipp pp P pelLs Blades as a Base fp Pred6o mg P ppelLs b d ced Press :e Fuo atipps," Jp mal of fLe Socieh of Naval Archikos of 3apm,Voll4S,mp3344,19SO E Huse, ' he Mal,mit de md Dishbutipp of P pellff b d ced SmEace Fp es pp a Si gle Spew Ship Model, " Np~wegiap Ship Model E pffimept Tpk Publication, No 100, 1968 M kkehata & H Fmm ki "A alytical Chafftffi tics of Oscdlati g Press :e Dishibutipp above aP ppells," Jommal of fLe Socieh of Naval Archik P s of Japap, Vol.
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From page 340... ...
Jcp m The mthors should be con rcml.ned for their efforts to make clear the solid boundary effect of c Unite flat plate on the pressure fluctuation induced by c wing I have the following questions (1) Fig 6 sh ws fnat there is se y large difference of amplitude of plessme fluctuation between QCM Ed SDM, especially in She aft part of the plat This difference would be due to the consideration of trcilmg vo tices shedding from She nailing edge of the put in QCM Does f is difference bee me smell, ffthe aft part of She flat plat was lengthened?
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From page 341... ...
was applied to on both the camber md the wing surfaces (2) We considered always She phase difference m our calculation We show the pressure Duct ctipms of components with time et x/c=3 0 in Fig A-1 in case of Fig 7, md gnat m Fig A-2 in case of Fig 11 From these Figures, w under t md that in case of Fig 7 the phase difference between unsteady md velocity 0 1 components is so large that two components cancel to each other, on the other h md, in case of Figll, She phase dfffe~ences among thee components are smell, then She total amplit de is nearly equal to sum of th ee components (3)
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