SMITHSONIAN IWISCELLANEOUS COLLECTIONSVOLUME 93, NUMBER 4
PIONEER WIND TUNNELS(With 4 Plates)
BYN. H. RANDERS-PEHRSONAssistant, Division of Aeronautics, Library of Congress
(Publication 3294)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONJANUARY 19, 1935
BALTIMORE, MD., U. 8. A.
PIONEER WIND TUNNELSBy N. H. RANDERS-PEHRSONAssistant, Division of Aeronautics, Library of Congress(With 4 Plates)In a paper read before the Royal Society in 1759 John Smeatonpresented the following very neat outline of the various methods thatmay be used for aerodynamic research : *In trying experiments on wind mill sails, the wind itself is too uncertainto answer the purpose ; we must have recourse to an artificial wind. Thismay be done two ways ; either by causing the air to move against the machine,or the machine to move against the air. To cause the air to move against themachine, in a sufficient volume, with steadiness and the requisite velocity, isnot easily put in practice : To carry the machine forward in a right lineagainst the air, would require a larger room than I could conveniently meetwith. What I found most practicable, therefore, was to carry the axis, whereonthe sails were to be fixed, progressively round in the circumference of a largecircle.Technical difficulties prevented Smeaton from using a wind tunneland prompted him to adopt the whirling machine, invented in 1746by Ellicott and Robins. This and other inferior methods of researchwere in use long after wind tunnels had been constructed and foundsatisfactory. Thus, Eiffel spent much time dropping plates from thetower bearing his name before adopting the wind-tunnel method
;
Langley and others used whirling machines, while many used naturalwind, which Smeaton had already found to be unreliable.
F. H. WENHAMThe distinction of being the first to introduce the wind tunnel be-longs to Francis Herbert Wenham, founder member of the Aero-nautical Society of Great Britain, who read at its opening meetinghis classical paper on " Aerial Locomotion ". In 1871 this Societydesired to undertake systematic aerodynamic experiments to obtain
" data on which a true science of aeronautics can be founded ". Asubscription fund was established ; an instrument designed by Wenham
' Smeaton, John, Experimental enquiry concerning the natural powers ofwind and water, p. 38, London, 1794.Smithsonian Miscellaneous Collections, Vol. 93, No. 4
2 SMITHSONIAN MISCEI.LANEOI'S COLLECTIONS VOL. 93
was approved by the experimental committee and was constructedby John Browning, an optician and member of the Society. It wasset up at Messrs. Penn's Marine Engineering Works at Greenwich,where the world's first wind tunnel experiments took place.The tunnel was a wooden trunk i8 inches square and lo feet long,llirough it was directed the blast from a fan, driven by a steam en-gine. The wind velocity was measured with a water gauge, variousspeeds up to 40 miles per hour being used. The wind was not steady,considerable fluctuations making the observations difficult. The di-rection of the wind was tested with a vane and said to be fairlystraight, although there is no mention of a wind straightener of anykind.The balance was exhibited and explained to the Society by Mr.Wenham. It consisted of a vertical steel spindle, supported on ahardened steel center. Through an eye at the upper end of the spindlepassed a horizontal weighing beam, supported by a cross pin axle. Thelong end of the beam carried the testing planes which could be set atvarious angles of incidence while they were always kept at right anglesacross the current. The short end carried a sliding counterweight soas to balance the testing plane. The drag was measured by a springsteelyard connected to a lever from the vertical spindle, close to thebase of the machine. The lift was read ofif by a vertical spring steel-yard.The balance with the testing planes was placed in front of thetunnel at a distance of 2 feet, a wooden shield covering the balanceand leaving only the planes exposed to the wind. Lift and drag weremeasured simultaneously, two persons making the observations. Onlyplane surfaces were tested, the largest being 18 inches across, thesame width as the tunnel. They were placed at various angles from15° to 60° ; tests on smaller angles were found to be very desirablebut could not be achieved with the instrument at hand.In spite of the crudeness of the tunnel and the shortness of the timeallotted for experiments, the results were the most satisfactory of thekind obtained to that time. The experiments were very encouragingto aviation enthusiasts, as they proved that the lift at small anglesexceeds the drag to a much greater extent than had previously beensuspected. The desirability of a large aspect ratio and the location ofthe center of pressure near the leading edge were also demonstrated.The test data were published in tabular form in the Report of theAeronautical Society. These tables were widely used and were alsomade the Ijasis for actual conslructi(Mi, particularly by Thomas Moy
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSONfor his " aerial steamer ", the first large power-driven airplane modelto rise from the ground in tethered flight/Twenty-five years later Wenliam expressed the wish that he mighthave an opportunity to build a large tunnel that would convey a current
" at rates varying from a gentle breese, up to a tornado that could ripthe clothes off your back, or blow you away like a feather, but noflying man should mind this effect." In 1900, at the age of 76, heactually rigged up a fan blower for experiments ; it ran at 1,700 revolu-tions per minute and gave a current of 25 miles per hour. Apparentlyit was driven by hand, as he says : ^
I could not get beyond this as it absorbed all my strength to work it, stillthe current was definite and steady with proper arrangement to measure liftand drift [i. e., drag]. I attached various models in the blast, consisting ofdifferent forms of supporting surfaces. 25 miles an hour would be a sufficientspeed to begin to fly with. HORATIO PHILLIPSNext to use a wind tunnel was another Englishman, HoratioPhillips. He produced his air current by means of a steam jet, hopingin that way to avoid the fluctuations of the wind which had marredWenham's experiments.
Fig. I.—Phillips' wind tumiel, 1884.
Phillips' tunnel was 17 inches square and 6 feet long. Attached toone end was " an expanding delivery tube of sheet-iron ", which was6 feet long, 12 inches wide where it entered the box, contracting to8 inches, and again expanding to 2 feet. In its narrowest part wasintroduced a ring of iron pipe pierced with holes, through which steamwas fed from a large boiler under 70 pounds pressure. This producedby suction an air current in the square part of the tunnel. In order toincrease the speed of the current, the square box was partly closed by a
^Aeronautical Society of Great Britain, 6th Ann. Rep., pp. 75-78, 187 1
;
7th Ann. Rep., pp. 6-12, 1872; 9th Ann. Rep., pp. 6-7, 1874.
^ Unpublished letters from F. H. Wenham to Octave Chanute, now in theLibrary of Congress.
4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93
solid packing of wood, leaving a space 10 by 17 inches in cross-section,where a speed up to 60 feet per second was obtained, as measured by awater gage.The balance consisted of two uprights, pivoted at the base and con-nected by a horizontal wire at the top. This passed through eyes ontwo stifif wires attached to the leading edge of the testing surface. Dragwas measured by weights in a scalepan, attached to the model mountingby a string running over a pulley, and lift was measured by a weightsuspended under the testing surface at the supposed center of pressure.The balance was pushed into the tunnel where the current was swiftest,so that the scalepan was outside the tunnel, and the suspended weightin a hole in the wood packing.^4 9Fig. 2.—Phillips' balance.While Wenham studied planes only, Phillips turned his attention tocurved surfaces. His were the first systematic studies of cambered air-foils, a subject about which practically nothing was known before.Phillips noticed the partial vacuum above the airfoils. He patented anumber of profiles, and introduced the downward curving leading edge,now in almost universal use. Several of the airfoils developed byPhillips had a maximum lift-to-drag ratio of about 10, an efficiencyadequate for pioneer flying and not known to have been surpassedbefore the arrival of modern wind tunnels.^The " Venetian blind " airplane built by Phillips, on the basis of dataobtained in his wind tunnel, readily lifted itself in tethered flight, andwas, with its cambered surfaces, a distinct improvement over itspredecessors. LUDWIG MACHDr. Ludwig Mach of Vienna in 1893 was the first to use a windtunnel to photograph the flow of air. The tunnel had a cross sectionof 18 by 25 centimeters ; one side was of glass and the others black onthe inside. The air was sucked through by means of a centrifugal fan
* Engineering, vol. 40, pp. 160-161, illus., London, Aug. 14, li
"British Patent, no. 13,768, 1884; and no. 13,311, 1891.
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON
at the rate of lo meters per second. A piece of wire mesh over theopening served to straighten the current. By the use of silk threads,cigarette smoke and glowing particles of iron, the flow could be ob-served. Streams of heated air were also introduced, invisible to theeye, but recording on a photographic plate. A series of good flowphotographs was obtained.*JOHAN IRMINGER AND H. C. VOGTThe first wind tunnel measurements of pressure distribution weremade by Johan Irminger, and H. C. Vogt, of Copenhagen. Vogt, whowas a marine engineer, had made extensive studies on sails and airpropellers and had found that the partial vacuum on the leeward sidewas responsible for the greater part of the thrust. Phillips was firstto notice a rarefaction, but did not press his investigation of this factorvery far. Vogt, in conjunction with Irminger, director of the Copen-hagen Gas Works, undertook a series of wind-tunnel experiments toestablish this fact conclusively.
Fig. 3.—Irminger and Vogt's tunnel, 1894.There was at the gas works a smokestack too feet high and 5 feetin diameter, serving a large number of gas furnaces. In order to utilizethe draft in this chimney for experimental purposes, an opening wasmade in its side and a rectangular box inserted, 40 inches long and4i by 9 inches inside cross-section. The inside of the box was polishedand a shutter was used to control the speed of the air current, whichranged from 24 to 48 feet per second.To determine the pressure distribution on plane surfaces, two piecesof sheet iron were placed i/io inch apart, joined along the edges toform a shallow closed box. To the interior of this a water gage was
* Zeitschr. LuftschifFahrt und Phys. Atmosphare, vol. 15, pp. 129-139, pis.I-III. i8q6.
6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93
connected by means of a pipe. A number of small holes were made inboth surfaces, of which one at a time was opened. Two such testingplanes were used ; both were i^ inches wide, one 4^ inches long, reach-ing entirely across the tunnel, the other 2-V inches long. The testing
Section X-y
Fig. 4.—Pressure measuring apparatus used by Irminger and Vogt.planes were placed in the middle of the tunnel and could be set atdifferent angles that were indicated by a pointer on the outside.Measurements of pressure distribution were also made on bodies ofvarious shapes, as prisms, spheres, etc., and on models of buildingsand gas tanks.
^
Ingenioren, p. loi, Copenhagen, 1894.Inst. Civil Eng., Minutes of Proc, vol. 118, pp. 468-472, 1894.Engineering, vol. 60, pp. 787-788, illus., London, Dec. 27, 1895.
NO. 4 PIONEER WIND TUNNELS—-RANDERS-PEHRSONCHARLES RENARDCol. Charles Renard, constructor of the famous airship La France,conducted a large number of aeronautical experiments at the fitablisse-ment Militaire de Chalais Meudon, of which he was the director.Renard continued his experiments during a long period of years andemployed a variety of methods and equipment. The details weresecret at the time, and the information available is still meager.
Fig. s.—Renard's tunnel, iSome time during the latter half of the nineties a wind tunnel wasused. It was cylindrical, 80 centimeters in diameter and 4 meters long.The wind was produced by a blower fan and said to be " violent ".Fourteen meters per second is given in a published chart. There is nomention of any means for straightening the wind.In his tunnel Renard studied the stability and critical speed of air-ships.* Most of his equipment—balances, testing models, etc.—are pre-served in the aeronautical museum at Chalais Meudon.SIR HIRAM MAXIMFor the construction of his giant airplane. Sir Hiram Maxim realizedthe necessity for scientific data and utilized a number of testing devices.Among these was a wind tunnel which was in operation in 1896.Maxim's tunnel was a wooden box 12 feet long and 3 by 3 feet insidecross-section, connected with a shorter box 4 feet square. Two air-screws on the same shaft, placed in the wider section and driven by aloo-hp. steam engine, blew the air through the tunnel. To straightenthe airstream a number of wooden slats were placed in the tunnelhorizontally, vertically, and diagonally. The objects to be tested were
* C. R. Acad. Sci., vol. 138, p. 146, June 6, 1904.Aerophile, vol. 12, pp. 153-155, July 1904.IV congres Internationale d'aeronautique, Nancy 1909.rapports et memoires, p. 241.Aeronautiquc, vol. 6, p. 84, illus., Paris, April 1924. Proces-verbeaux,
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93placed in front of the tunnel and the balance measured both lift anddrag.Sir Hiram tested airfoils, struts, and airplane parts in his windtunnel, and also the efficiency of steam condenser pipes."PAUL LaCOURTwo wind tunnels were used by Paul LaCour, of Askov, Denmark,for windmill research. Both were made of sheet iron, cylindrical, 2.2meters long ; one was i meter in diameter and the other ^ meter. Thewind was produced by electric blower fans and straightened by radialfins inside the tunnels. A speed of 10 meters per second was used, andthis was kept constant by controlling the fan speed, which was readfrom a tachometer. The testing surfaces and windmill models wereplaced I meter out in front of the tunnel."ETIENNE MAREYEtienne Marey, of Paris, famous for his chronophotographic studiesof animal locomotion, in 1899 turned his attention to obtaining photo-graphs of air in motion. This was achieved by the use of narrowbands of smoke in a small, vertical wind tunnel.The tunnel was 20 by 30 centimeters in cross-section, with frontand sides of plate glass and the back covered with black velvet. Theair was drawn down through the tunnel by a small suction fan andstraightened by passing through fine silk gauze of very even weave.Smoke was supplied through a row of fine tubes at the top of thetunnel and descended in straight bands, clearly showing the flow pastsmall models that were inserted. Photographs were taken by meansof a magnesium flash, burnt in a ventilated box close to one side ofthe tunnel.Among the scientists that were interested in these experiments wasSamuel P. Langley. He provided funds from the Smithsonian Insti-tution for their continuance, and the next year Marey built a new andimproved tunnel. This was 20 by 50 centimeters in cross-section, andthe smoke tubes, 60 in number, could be made to vibrate laterally10 times a second.
° The Aeronautical Annual, 1896, pp. 50-61, illus., Boston.Maxim, Hiram, Artificial and natural flight, pp. 50-61, illus., New York andLondon, 1908.
"'LaCour, Paul, Forsogsmollen, pp. 14-15, Copenhagen, 1900.Ingenioren, no. 10, Copenhagen, 1897.
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON 9The speed of the air at any point was indicated by the undulationsof the smoke bands caused by these vibrations. Judging from someof the photographs where the measuring rod is seen, the speed wasabout 30 centimeters per second.A number of very beautiful flow photographs were obtained byDr. Marey." A. F. ZAHMThe first complete wind-tunnel laboratory, equipped for a widerange of aerodynamical experiments and with instruments capableof exact measurements, was devised by Dr. A. F. Zahm and erectedon the grounds of the Catholic University of America in the winterof 1901.This laboratory was made possible by Hugo MattuUath, inventorof a giant flying boat, Dr. Zahm having agreed to become, during hisspare time, the consulting engineer of Mattullath's company.The laboratory building was a one-story frame structure 30 by 80feet and housed a wooden tunnel 6 feet square in cross-section and40 feet long, with windows in the ceiling and walls. The wind wasdrawn through at a speed of 27 miles per hour by a 5-foot suctionfan, driven by a 12 hp. electric motor. The intake end was coveredwith one or two screens of cheese cloth or wire mesh to straightenthe wind. The air speed was held constant within a fraction of i per-cent by a boy with a tachometer and a rheostat, controlling the fanspeed. For some researches movable liners were introduced in themain tunnel, making the current contract trumpetwise to gain speed,then run straight in a narrower stream, and finally discharge as anopen jet in the after part of the main tunnel. The testing model wasplaced either between the parallel sides, where the wind speed wasgreatest, or in the center of the current where it entered the experi-mental chamber.The wind tunnel was equipped with a variety of instruments in-vented by Dr. Zahm for showing the character of the air flow andits action on the models.
" C. R. Acad. Sci., vol. 131, pp. 160-163, Julj' 16, 1900; vol. 132, pp. 1291-1296, June 3, 1901.Ann. Rep. Smithsonian Inst., 1901, pp. 14, 332, 337-340, pis., 1902.Journ. phys. theroique et appliquee, 4th ser., vol. i, pp. 129-135, illus., 1902.Scientific American, n. s., vol. 86, pp. 75-76, illus., Feb. i, 1902.Nogues, P., Recherches experimentales de Marey sur le mouvement dansI'air. France. Min. de I'air. Publ. sci. et techn., pp. 94-97, illus., 1933.
10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93The air speed was measured with a pitot-static tube, connected withan extremely sensitive manometer." This consisted of two thin metalcups, inverted over coal-oil and supported from opposite ends of aweighing beam. Two tubes, one from underneath each cup, werejoined respectively to the inner and outer tubes of the speed nozzle.To test the accuracy of this instrument a " balloon anemometer " wasdevised. A toy balloon floating downstream intersected on its waytwo thin pencils of light focusscd on the moving plate of a longcamera constructed for that purpose. This was an adaptation of theingenious chronograph previously invented by Dr. Zahm for his re-searches on the speed of bullets."The manometer was also used for the study of pressure distribution.Several aerodynamic balances were developed, among them the wiresuspension balance, now in general use, and the bell crank balance,now often called the N. P. L. balance. It was called the " universalpressure balance " in 1902, and consisted of a bell crank with hori-zontal axle mounted on knife edges above the tunnel, having a gradu-ated horizontal arm with scalepan and sliding weights, and a verticalarm running down through a streamline wind shield to hold the modelsin the air stream.The laboratory was built and equipped early in 1901 and a descrip-tion was communicated to the American Association for the Advance-ment of Science June 30, 1932, and was privately printed (200 copies)in a small pamphlet which is now a great rarity."Mattullath died in December 1902, and the flying-boat project wasabandoned, but the scientific work in the laboratory went on inter-mittently until 1908. Money grants for special researches were madeby the Smithsonian Institution and the Carnegie Institution in 1904and 1905. Results of the investigations were communicated to scientificjournals and societies. The most important of these was Dr. Zahm's
" Exhibited before the Washington Philosophical Society, May 24, 1902
;
described in Phys. Rev., vol. 17, pp. 410-423, December 1903. In this paper,p. 417, the term " wind tunnel " is used for the first time." The resistance of the air determined at speeds below one thousand feet asecond, with description of two new methods of measuring projectile velocitiesinside and outside the gun. Thesis, Johns Hopkins Univ., 46 pp., illus., 1898."New methods of experimentation in aerodynamics; outline of some experi-ments made by H. Mattullath and A. F. Zahm, at the Catholic University ofAmerica. Paper communicated to the meeting of the American Association forthe Advancement of Science, at Pittsburgh, June 30, 1902. 12 pp., illus., signedA. F. Zahm, Washington, D. C, 1902.
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON II
epoch-making paper on "Atmospheric Friction 'V° read before thePhilosophical Society of Washington, February 27, 1904.This paper disclosed for the first time the fact that skin frictionis responsible for the major part of the total drag. The tests weremade in the wind tunnel on carefully constructed boards up to 16 feetlong suspended on the wire balance.Tests were also made on various spindle- and fish-shaped bodies,establishing the best form for airship hulls and giving, for the firsttime, the reason why the now universally accepted torpedo shape ispreferable. The resistance of wires, struts, wings, and other airplaneparts was also studied.The tunnel was also used for instruction at the University, severalstudents taking part in the experiments. Occasionally, special testswere made for other investigators ; for instance, Octave Chanute senta stufifed buzzard for lift and drag measurements, and Emile Berlinerhad a monoplane model tested.WRIGHT BROTHERSThe Wright Brothers' gliding experiments at Kitty Hawk in 1901,although they seemed successful to other observers, were very dis-appointing to the Wrights themselves, as the new glider did not at allperform according to their calculations based on the aerodynamictables of Lilienthal. On returning to Dayton in August, they decidedto find out by laboratory methods what was wrong.Their first testing machine consisted of a bicycle wheel mountedhorizontally on a spar projecting from the front of a bicycle. Therelative aerodynamic efficiency of various surfaces was found bymounting them on this wheel, balancing one against the other andriding the bicycle at a fairly constant speed.Next they sent the blast from a fan through a square tube andmounted their surfaces as blades on a vane in the stream, balancing acurved surface against a plane surface.By the middle of October 1901 a small wind tunnel was completed.It was 16 inches square inside and about 6 feet long, with a glass top.The wind was forced through by a blower fan, and passed through a
"Atmospheric friction with special reference to aeronautics, pp. 237-276,diagrs., 1904. From Bull. Philqs. Soc. Washington, vol. 14, 1904.Also printed in England: Atmospheric friction on even surfaces, withcommentary note by the Rt. Hon. Lord Rayleigh, F. R. S. Reprinted from thePhilos. Mag., July 1904, pp. 58-67, diagrs.
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93honeyconil) wiiul-straightencr. The air speed was estimated to be40 feet per second.The balance was based on the principle of using the normal pres-sure on a plane surface to measure the lift of an airfoil. The wingmodel and the normal plane were mounted on separate horizontalcross-stream bars so linked together that the wind lift on the model
Fig. 6.—Schematic drawing of the Wright Brothers' halance, based on a photograph.
tended to move it across stream. The drag on the normal plane wouldtend to resist this movement. When the two were exactly balanced,the ratio of lift to the resistance of the normal plane was indicatedby a pointer.A l)alance of similar construction was later used by Orville Wrightin his wind tunnel in Dayton."
"Warner and Norton, Wind tunnel balances. U. S. Nat. .'\dv. Comni.Aeronautics, Rep. no. 72, pp. 39-40, 1920.
NO. 4 PIONEER WIND TUNNELS RANDEKS-PEHRSON I3About 200 wing models made of sheet metal were tested in thewind tunnel. Each model was tested at 14 different angles of inci-dence, varying from 0° to 45°. Tests were also made to ascertainthe effect of varying the aspect ratio, of superposing surfaces, etc.Great care was taken in making the tests ; no one but the o1)server wasallowed near the tunnel while it was in operation, and he kept the sameposition during the extent of the test, in order not to disturb the aircurrent. The results were meticulously noted, and when completedthey formed a valuable collection of aerodynamic tables which werelater used by the Wrights as the basis for their design. AroundChristmas 1902 these experiments came to an end, and the apparatuswas taken down."This construction and the Wriglit Brothers' investigations there-with formed one of the chief factors leading to their success at KittyHawk on December 17, 1903.
T. E. STANTONThe first wind tunnel at the National Physical Laboratory in Lon-don was set up several years before aeronautics became a subject ofresearch at that institution. This predecessor of the great modernN. P. L. tunnels was built in 1903 by Dr. Thomas E. Stanton, forinvestigation of wind pressure on surfaces and structures.Stanton's tunnel was vertical, the upper part a cylinder 2 feet indiameter and 4? feet long, terminating in a square box 4 by 4 feet,and I foot 3 inches deep where the balance was inserted. Underneaththis, connected by a shorter length of pipe of the same diameter asthe upper part of the tunnel, was the fan chamber. The fan, whichproduced the wind in the tunnel by suction, was driven by an electricmotor and could be regulated to give air speeds from 5 to 30 feet persecond.The balance comprising a horizontal lever carried on knife edges,had a sliding scale, and a scalepan with a dashpot for damping thevibrations. It was inserted in the center part of the tunnel, so thatthe model projected into the cylindrical section. The long arm of thelever was hollow and could be connected with a sensitive manometer
"Aeronautical Journ., vol. 20, pp. 73-74, July-Sept. igi6.Unpublished letters of Wilbur Wright to Octave Chanute, now in theLibrary of Congress.
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93for measurement of pressure. The speed of the current in variousparts of the tunnel was measured by a pitot-static tube connected tothe manometer.
Fig. 7.—Stanton's tunnel, 1903.
Experiments were made in this very carefully constructed littletunnel to determine the resultant pressure and the distribution ofpressure on round, square, and rectangular thin plates, normal andinclined to the current, on lattice work, cylinders, and finally on modelroofs and bridges. The tunnel was still in use at the time when the4-foot N. P. L. tunnel was constructed.'*
^' Inst. Civil Engineers, Minutes of Proc, vol. 156, pp. 78-139, illus., 1904.Great Britain Adv. Comm. Aeronautics. Rep. 1909-ia, p. 14.
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON I5
G. A. CROCCOIn the fall of 1903 an aerodynamical laboratory was establishednear Rome by the " Brigata Specialisti " of the 3rd Italian EngineerCorps. The laboratory was built under the direction of Lieutenant,now General, Gaetano Arthuro Crocco. It was well equipped withresearch apparatus, including, as the most prominent part, a windtunnel of novel construction.By means of a 2.5-meter centrifugal fan and a 30-hp. electric motor,air was driven into a large cylindrical chamber like a gasometer, 5meters in diameter and 3.5 meters high, which served to overcometurbulence and fluctuations. From here the wind was conveyed througha tunnel, the end of which was inserted in the laboratory wall, fan andair tank being outside. The cross-section of the mouth of the tunnelwas I by I meter square ; also a cross-section of 80 by 80 centimeterswas used, and cylindrical mouthpieces of smaller diameter.The tests were made in the open jet, balance and models beingmounted on a support on the floor, on a light carriage, or sometimeson floats swimming in water. The principal balance, constructed byCrocco in 1904, was an improvement on the dynamometric balanceof Renard.For some researches the part of the laboratory where the air entered,was closed off to form a second air-straightening chamber, and thewind continued through a tunnel within the laboratory building. Thistunnel was 8 meters long and 0.85 by 1.50 meters in cross-section."The investigations at the laboratory of the Brigata Specialisti werechiefly concerning air propellers and the resistance and stability ofairships. The construction of the first Italian military airship in 1907was based on these tests.Results of the investigations were also presented in several im-portant papers by Crocco, published in various places, and reprintedin his " Problemi aeronautic!, degli albori fino alia guerra." 524 p.,illus., 27 pis. (Roma, A. Stock, 1931).
D. RIABOUCHINSKYThrough the efforts of D. Riabouchinsky, a wealthy patron ofscience and himself a scientist, Russia took its place in the front rankwith regard to pioneer aerodynamic research.
" Boll. Soc. aeronautica ital., vol. 2, p. 209, illus,, Nov.-Dec. 1905.Marchis. Le Navire aerien. Appendix, pp. I22a-i27a, illus. Paris, 1909.
i6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93
U
[IH
NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON 1/At Koutchino, not far from Moscow, Riabouchinsky erected, athis own expense, a complete aerodynamic laboratory with severalbuildings and an adequate stafif. According to a suggestion by Prof.N. E. Joukovsky, the laboratory was equipped with a cylindrical windtunnel, 14.50 meters long and 1.20 meters in diameter. Wind wasproduced by a suction fan, driven by an electric motor. Great painswere taken to render the wind uniform. After several experimentsthat did not give satisfactory results one end of the tunnel was en-closed in a cylindrical hood 2.2 meters in diameter and 3.5 meters long,coaxial with the tunnel itself. This admitted the air in such a waythat a sufficiently even current was obtained. The testing section, inthe middle of the tunnel, was provided with windows, from which theaction of models could be observed.A great variety of aeronautical and hydrodynamical subjects werestudied. Among the researches in the wind tunnel, the experimentswith propellers, particularly lifting propellers were important. A bul-letin was published by the laboratory in six large issues, the lastin 1920.'° LUDWIG PRANDTLWith the construction of the first wind tunnel at Gottingen we areapproaching modern times. This was the first return-flow tunnel,built by Dr. Ludwig Prandtl for Motorluftschif^studiengesellschaftand completed in July 1908.^This tunnel was superseded in 1916-17 by a much larger tunnel withopen jet and return flow, which is now called the Gottingen type.
A. RATEAUWith the aid of the Societe d'fitudes de Locomotion Aerienne,A. Rateau built a wind tunnel in Paris in 1909. A 4-foot propellerblew the air into a rectangular chamber, 1.60 meters in cross-section,with an outlet contracting to a nozzle 70 centimeters square. Thecurrent was straightened by passing between a number of wooden
'^ Institut aerodynamique de Koutchino. 8 pp., 17 pis., St. Petersbourg, 1905.Institute aerodynamique de Koutchino, 1904-1914. Moscow, 1914.Bulletin de I'lnstitut aerodynamique de Koutchino. Fasc. 1-6. Moscow,1909- 1920." Motorluftschiffstudiengesellschaft m. b. h. Berlin, Jahrbuch 1907/08-1912/13.Zeitschr. Ver. deutsch. Ingenieure, vol. 53, pp. 1711-1719, Oct. 16, 1909.
l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93
slats, and the nozzle made possible speeds of up to 35 meters persecond.'"
• GUSTAVE EIFFELGtistave Eiffel built his first wind tunnel on the Champ de Mars in1909. It was the open-jet nonreturn tunnel with an airtight testingchamber, known as the Eiffel type. The air current was cylindrical,1.5 meters in diameter, later enlarged to 2 meters.^In 1911 Eiffel moved to Auteuil and built a new and larger labora-tory, which he later turned over to the French Government.NATIONAL PHYSICAL LABORATORYThe N. P. L. built its first large wind tunnel in London in 1910. Itwas 4 by 4 feet in cross-section and was supported inside another tun-nel 8 by 8 feet. The space between the walls of the two tunnels was areturn passage for the air, which was drawn through the 4- foot tunnelby a Sirocco fan, driven by a 15 hp. engine.^This tunnel was not very satisfactory and was replaced in 1912 witha closed-jet nonreturn flow tunnel.The tunnels of Prandtl, Eiffel, and the N. P. L. have been verybriefly described, as their main features are generally known, and fulldescriptions are readily available.^" They end the pioneer period andbegin a new era in wind-tunnel history. Before these three laboratorieswere established, powered flight had become a proved fact, and air-ships had met with considerable success. The necessity for reliablelaboratory research soon became universally recognized and wind-tunnel laboratories were built and maintained by governments andinstitutions, as well as by private agencies.
"Aerophile, vol. 27, pp. 266-268, illus., June 15, 1909.Soc. ingenieurs civils France, Mem. et C. R. Traveaux, vol. 65, pp. 61-78,illus., July 1912." Eiffel, Gustave, Installation d'un laboratoire d'aerodynamique. Paris, 1910.La resistance de I'air et Taviation, experiences effectuees au Laboratoire duChamp de Mars. Paris, 1910. The resistance of the air and aviation, experi-ments conducted at the Champ de Mars Laboratory. Translated by Jerome C.Hunsaker. London and Boston, 1913.
"Great Britain Advisory Committee for Aeronautics, Rep. 1909-10, pp. 14-15,2 folded plates.Flight, vol. 2, pp. 226-227, March 26, 1910.^ Zahm, A. F., Report on European aeronautical laboratories, SmithsonianMisc. Coll., vol. 62, no. 3, 23 pp., 11 pis., 5 figs., 1914.
NO, 4 PIONEER WIND TUNNELS RANDERS-PEHRSON I9
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20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93
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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93, NO. 4, PL. 1
1. MAXIM'S Tunnel, 1896
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2. LA CouR's Two Tunnels, 1897
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93, NO. 4, PL. 2
Marey's Tunnel, 1900
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93, NO. 4, PL. 3
1. A. F. Zahm's Aerodynamic Laboratory, 1901
2. ZAHM'S Tunnel with intake Cone removed
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93, NO. 4, PL. 4
Balance and Group of Test Models Used in Zahm's Tunnel
RIABOUCHINSKY-S TUNNEL, 1905