1、a - N * NcTTht5 120112TECHII CAL MEORAiUMSNATI ONA ADVISORY COMIIiITTEE FOR AERONAUT I CS ISTRESSES PRODUCED IN AIRPLANE WINGS DY GUSTS By Hans Georg Kissner Zeitschrift fr P1ugtechni unci MotorlutscMfahrt Vol. 22, lbs. 19 and. 20, Oct. 14 and. 28, 1931 Verlag von R. 01d.erooiir, Munchen und Ber1iIA
2、/ -NAIIONAL TECHNICAL INFORMATION SERVICE - _ L - * 44 kIt aSgton SUDJECf TO CHA1GE Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NATIONAL ADVISORY COIMtTTEE POR ARONAUTICS TECICALMEMORAi1DUi. iTO. 654 STRESSES PRODUCED IN AIRPLANE Y1TGS 3Y.USTS*By
3、 Hans Georg Kussner Vhereas, in calm air,.: the strses in an airpl.ne wing depend on the airplane characteristics aid on the Di-lot, the latter has little or no influence on the magni-tude of such stresses in gusty weather from the point of view of mai.taining flight schedule an.d cruising seed. Con
4、seuently.,Uis airplane must be able. t.o withstand such strosse.s in any case. Ame irst infbrmation on stresses gusts was col-lectd by 7 Hoff in 1914* At that time there was no need to attach any special significance o.suchstreises, becai.se the speed range of the airplane, i.e., the ratio of maximu
5、m speed in uniform level flight to stalling speed was, in most cases, essentially lower than 2, and flying was, in the main, confiod to fair weather. But since that time the airplane has undergone onormous changes and improvements until to-day air traisportation has developed until it is practically
6、 ithperativo to fly under bad.as well as good. weather conditions.D In order prehensive conception of the flow phenomena in the open air, let us first glance over sone meteorological rep.ort: . 1. Official entry of telephone conversation with weather forecasting station, Tempelhof, Oct. 10, 1929: I
7、11At this station the following vertical components of gusts have been recorded: Normal (on cumulus clouds) . 2 Very frequently in bad weather zones, 6 Rare maxima, . . 12velocity 1f: to 4 ni/s to 8 rn/S ,q 13 ui/s i (Signed) Thalau. 3eanspruchung von Pl-igzeiigflgeln clurch Boen.“ Zeit-schrift fur
8、Flugtechnik und Motorluftschiffahrt, Oct. 14, 1931, pp. 579-586; and Oct. 28, 1931, pp. 605-615. *Tecilnische Berichte der Plugzeugmeisterei, Vol. 1, 1917, p. 61.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 H.A.C.A. Technical Memoranthxrn-1o. :G
9、54 2. Letter from German Naval. Ober4iatory, Meteorolog-ical Research Institute, to the D.V.L O , October 25, 1929: “In answer ,toyour reQuest, we subrnit the latest reports- ofour forecasting station: - No exact measurements on the vertical velocity in :usts aie available at this post. 7e can only
10、give approximate values based. upon our xDeriences in numerous flights in clouds and. - gusts. - The most violent bumps are always ecountered at the front of an advancing gust roller, while at its upper border and above it the intensity is much abated In this respect only gust fronts with cold, air
11、inflow areas are beiig considered. - - “Theorder of magnitude. of the. vertical up and downward velocity doponentsvaries between 5 - and. 20 rn/s. . - - Sidling into or flying through a cumulus, the strongest gusts are encountered diectly at tie bordor of the cumulus; 5 to 10 rn/s may be con-sidered
12、. as normal for the vertical component of the velocity, Below the Cu. an up current of from 2 to 5 m/ prevails. In bad-weather zones Sto 10 m/s.velocities have been noted quite frequently. -Bad-weather zones adcornpanied by gusts are most generally bound. - up with areas of inflow of cold air and wi
13、th the passing of a convorgence.* 15 to 20 rn/s -are considered rare mximurn in gusts. However, it ay be assumed. that the maximum val-ues of the horizontal components in bad weather ma:. also be those for vertical gusts, so that an extreme of 30 rn/s is still within the ambit : po.ssiiility. - *500
14、 P. Exner, Dynamische Meteorologie, Leipzig, 1917, p. 2;9. V. Schmidt,. Tioncr Sitzungs Bericht, Vol. 119, 1910, Pu, 1J.Ol. .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IT.A.C.A. Technical Meruoranclurn io. 654 3 This information is deduced. from
15、 airplane meteor-ograph records. Th above experiences are con-firmed br aerological data from pilot ballobn ascensions. The figures cited. are valid for dynamic pressures within the first few kilome-tors abovo thc.ground.(Signed) Unterschrift. 3. A. Lohr, Cloud Plying:* The view of a convection cumu
16、lus field is much more imposing. Tho Cu. formations of the onvec- tion, space evince a much mightier formof towering head than the . Cu. of the friction space; they rise lofty into the sky and conjire, through their sharp contrast in light and shadow effect, miraculous, magnificent pictures. Towerin
17、g from their midst are lofty thund.erheads, reaching upward as high as 6000 meters, The pronounced bumpiness at the border of such towering heads is, of course, well known. But the warning against attempts to fly through them can- -not be emphasized enough. They are invested by ver-tical gusts of fr
18、om 10 to , l5 rn/s velocity, whereas beneath an ordin,ary Cu. formtt ion the uprush of the air is not expected to be more than 2 to 4 rn/s and which, of, late, is so successfully utilized in sai.-ing flight-. Closely related to the vertical current w.th up-wel.li:ng Cu. heads are the caps over the C
19、u. which toa. large tent are ice formations and risen stratus layers peiiotrated by the towering head. The latter spread, out and, often rise along the flanks of the tower., Prom time to time veil-like stratus clouds are pushed up by the turbulent layer beneath, making one feel as though being above
20、 a smooth stra-tus layer in which the umulus fields with soft fountain forms are imbedded. 0 “Another important object in cloud flying is the observation of the restlessness of the air within and in the neighborhood of clouds. One case in point is the restlessness of the air in the van of a gust. Ob
21、viously, flight within or below i.t is avoided. But frequently we stated ahead of the oncoming roller. It was found that in a spread of from 3 to 5 km in the van of the gust sorae very pronounced vertical *Ueteorologische Zeitschrift, 1930, September issue.Provided by IHSNot for ResaleNo reproductio
22、n or networking permitted without license from IHS-,-,-4 1T.A.C.A. Tec.nical ernorandm.ie,.554 gus:t,s ao exist which, however, vanish immediately aftor,ono passes directly above thb gust roller, where the spaco directly behind: the gust head, in Particular, is very calm.“ 0. Lange, The Aerological
23、ConditiOns in Cumulus Clouds : * “Although the entire descent was made with idling enine, the instrurnonts:r.ecodod piactically the same altitude for 20 seconds at 3000 motors, and a ajn of over 100 meters in 40 seond.s at 2500 meters, which can only be explained: as bei-ng due to vertical movements
24、 in the air. - The sinking velocity of the airplane from 4800 to .300.0metes is 540 meters per minu.te, and. from 2600 to 1200 meters, it is 530 me-ters per minute, or approxirate1y 9 rn/s. According to this., the upwind at 3000 metCrs is about 8 m/s, and. 12 rn/s at 2500 moters. I : b,etween, theve
25、rtica. velocity is from 2 to 3 rn/s. : “ . Recapitulation: Tho records r :e,vl that the air .bodies of cumulus clouds by U foll“ot1ng weatheru are o1der than the surrounding air. , Tithin the cloud, a fairly huiid adiabatic .gradi:ent holds sway, the in-versions and isother.ms of t icinity are destr
26、oyedby the turbulenc,. but, a stroifger inversion at great-or heights acts as barrier Layer :. The vertical mo-tion does not extend uniformly oYer th whole cloud but fluctaates horizontally; the maximum recorded upwind velocity is 12 rn/s. Around. zeo temperature con,siderable ie formed on the airpl
27、ane; below zero we encountered hail, Aside from pross .une spots on the propeller the.airplane, being all-metal, shwed. no vi sibl damage. But the whole flight demonstrat-ed that it cannot be emphasized ehough not to fly through thunder clouds.“ (Compare the altitude t.LIe curve iTo. 4.) *3itrage zu
28、r Physik der freion Atmosphre, 1930, Zo. 2. ci 1Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N.A.C.A. Technical Memorandum !To,654 5 5.Goorgi.i., .The Airplane as0 iedium for Aerological ,Re,search:* - 1!The weather conditions of-the fiights on: J
29、uly 30, 1929, are charactrizest wind. The pr,ind flights this day are typical of the existiig 0 , vertical motions-in such cumuli. W.o have the records from three sailp1anes,: the “Luft,iinis., pilot Bedau, at 12.11 p.m., th .“Tien,“ pilot Kronf.eld, at 3.30 prn., and. the Rhonadler,“ pilot Gronhoff
30、, at 5.25 “p.rn. .which, in. -spit of the difference in the hours, show many common symbols of the vertical motion. The “Wient shows an almost uninterrupted climb from take-off at 950 rn.up to 3000 rn,. first in the dynamic upcurrent of the Wasserkuppe, then from 1500 mon in - the uprush.of a cumulu
31、s entered after leaving the mountain slope. The cumulus was traverse,d from base to top, so the vertical velocities at 1600,to 3000 mheight correspond to the rising air current in the -: cumulus. The maximum (5 m/s) , was reached between 22:00and-2?00 m. One sir rising fature of the theoljght.s is a
32、 distinct abatement in the ascend-ing-.air currentat around 1400 m altitude. Threc-ord of the “Wien,! showed only a short, bend in the altitude-time-curve, whereas in the ItLuftikusU it manifested at this height longer variations inp-and-down wind, very similar to those in the “Rhon-adler,“ but of c
33、ourse, of decidedly shorter eriod within the same level. The very violent vertical gusts ncountered at 1800 m, according to Groenhoffs record, are.particularly illuminating. Between the 51st and 53d. minute of flight the airplane was pushed. down 140 m iii a few seconds and, pulled up again 170 ui i
34、n the next. Two othersimi lar but less violent bumps followed immediately. .*Beit.rage zur Physil: der freien Atmosphare, 1930, No. 3.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Tchnicai Memoand.uru No.654 The :sliodkandth torsidn were so sevetha
35、t it tore the plywood covering over the fittingf the wing to the. fuselage. The evaluation of the gusts reveals a descending air. current of 9 m/s, and. an ascending current Of 10 rn/s where, of course, it should be borne in mind that these velocities still represent averages, even if only for a per
36、iod. of from 10 to 20 seconds. The altitude-time curve of the tLuftikus“ also discloses marked fluctuatIons in vertical cur-rent for this day. The upwind velocitt jumps at be-tween 1200 and. )500 in altitude also within a 4iery few seconds; from +4.1 to +0.8, then to +47, and agin to + 1.2 rn/s. Thi
37、s is suggestive of the exist-ece of very material vertical burrents in cumulus clouds, even if they do not develop into cuthulas nim-bus,: and their irnportaice in aviation is far from secondary because airplanes and. chiefly airships are subject to enOrmous stresses in such shdrt-ceriod vertical gu
38、sts. (Compare altitude-time cuvts Nos.5and 13.) . Georgii, Repoit on 11th Rhn Glider Met: 3edau first sailed in theipwind of the Vasser- kuDpe;n the 214th minute of his flight?, he con-nected withthe upcurrent of a cloud. which carried hith at moderate ratOf. climb to 1600 meters abso- lute altitude
39、. Aft?ethe first rise the upcurrentin the cloud abated :“thn suddenly in the 226th minute an abnorrrially powerful and Wholly unexpected current clutched. the airplane and. lifted it over 900 rnetrs within 3 minutes. The sudden ris.e was fol-owed by a drop in which the rate of descent in-creased to
40、approximately 25 rn/c, which later changed into spiral flight, in which Bedau then emerged. from ; the clo.:ve.tical mot ntog.eatacenngi cit1s, as : eyiienced by 3edaus barOgriitx the 226th inute, 1eds us. to. s.rise that ti. iipwin . in the imtlus is:c.aused by n eddy ith horizoatal or eveii verti-
41、cal xis, and th air currents o a ith.ii1tain loDe : offer many. possibilities, to enerato uchethiis.0 (Compare altitude-tirne curve o, 1.) 7“Moltchaoff; Structure of Squalls in the Open t-rnosphre* . (easueiierfts onHorizonta.Gu.sts; the 5:tructure of Vertical usts i Fundamentally Sirni-1a) : . . .
42、. UThe records from kites indicate the general d.ura-tio of Oah st at : from 0.2-to 0.3 seond although in isolated cases, gusts up to 12 sridshave been recorded. Fi;ure 1 shows one of such kite records. The gust lastdabout 4 ecoiid At esent we are making . oiiternperar r studies of gustsatdifferent
43、height s. (See fig. 1.) 8, W. Schmidt, The Strubtur of the In the summer ofl928 we were able to ex!i.ore a field. of abOii . lO X 10 rn in 25 different test sta-t.iloii on . t,h Aporn aipaat in Vienna. The test .pacng (2 rn), of “couise, was so wide that the small-est interferences escapod, but it b
44、rought“ot the major changes only more clearly. The 1ace was fa-oabie;.wee.ercidet crin havng the wind pass ovr. the field tO “the obsererpot whidh was placdfar e.iioughawayfrorn all bui.Idis sO togive the.win“clO.n land) , The best of the 17 ries“o Jjy 24, 12.14 p.m., sunny, very hot (over 30 0 0) ,
45、 wind corn-:prises 300 rcrd, iep.-eseiited “in .tlthe same manner (ral nstntaneous .isotachs). . . :. ,., :. 2. Because Of theiimited space, we epodue only sections of it. The incliy.i.dual. .p.icturesare .1.17. . apart; they are givei ,4ng ,oi.ps .of three at intervals o.f approximately 1 :se.coid
46、in, igue 3 , : *3eitrge zur Physik d.erfreien. Atrnosphre; 1930, No. 2. *7i$ner Sitz,.-Br, Vol. 13 Deuhe Forschung, 1930, No. 14, p. 58. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 N.A.C.A. Technical iAomorandum Nb. 54 This large cr0313 section
47、 substantiated the deduc-tions drawn previously: arkod v.ariation in flow y e-icity:vertically and horizon.tally frequntly faster -thving layers beneath slower onos, practically, no si of a real eddy (at least, not of tho orer of magn,itiido of several meters) entry of rapidly mov-ing masses. New in
48、formation was gained with respect to the transformation of such masses, hich in this case arrive usially in a moro horizontal direction, but subsequently appear to strighton up. The sur-prisirig feature is that the strongest contrasts of te velocity in such hurnpsfollow so closely along one another; two meters farther the velOcities
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