GREAT WIND TUNNEL

Evening Post, Volume CXIX, Issue 104, 4 May 1935, Page 18

GREAT WIND TUNNEL

AEROPLANE RESEARCH

' THE OPENING CEREMONY

frEAL TESTS OF DESIGN

(From "Tho.Post's" Representative.) '•■<:.' , ■'■■'■ ■■■'■■ LONDON, April 6.

A certain New Zealand engineer is justifiably, proud to have accomplished a very important work in this country. Yesterday, the Marquess of Londonderry (Secretary of. State for Air) officially opened what is probably the most up-to-date wind tunnel in the world. America has a larger one, but no country has one which is more «cientificially constructed and capable of sq; wide a range of research. Mr. GedrgV; N. Pill (of Auckland) is "responsible for the design of the building ahd'the'construction. Mr. Pill has been the : representative of Messrs. Boultbn and Paul, the main contractors, and has been in charge since July, 1932. Aeronautical engineers have designed the actual tunnel and mechanism, and all the accumulated knowledge on the subject has been available and improved upon. The British Thomson Houston Company designed the electric motor ■which drives the tunnel fan and installed the necessary electrical work lor the motor. The main balance used for, measuring the forces to which an aircraft is subjected when in the airstream was designed and installed by Sir Howard Grubb Parsons and Co., and other firms are responsible for lifts, ventilating systems, and other sections of the tunnel. . BUILDING AND PLANT. The building is not low and tubular, as its name would.imply. It is 90ft in height, and from the topmost tower a wonderful panorama of;' the country that surrounds the Royal Aircraft Establishment at Farnborough may be obtained.; Camberley, Aldershot, and all thevvfllages in this military area are visible, with the Hog's Back in the distanced The building is of steel and concrete, and the floor space beside the tunnel is great enough to hold the largest aeroplane built. The tunnel'itself is in the form of the capital letter C. In the gap the aeroplane-is mounted. In the mouth of the 16'wer arm-of the C is the great fan sucking-in the air and pushing it round, to come out again through the, 24ft jet at the end of the upper arm of the,C., ; A-3006 'hbrsfr-power electric motor turns the-.fan;at:Qver 200 revolutions a minute; generating! a wind across the working section of 200 miles an hour. During recent y.ears it has become evident that certain data obtained from small scale models may not be applicable with sufficient accuracy to the detail design of the full-size aeroplane.. With this tunnel the tests may be made on an/actual aeroplane or parts:pf aii'actual'.a'eroplane. What it means iis jhat.iristead of, testing an aeroplane moving at*2oo miles an hour in the.air, scientists may sit comfortably below or fin the aeroplane itself •with the engine running and have the exact conditions of an aeroplane moving through the air Jat 200 miles an hour. ■■;■■•■ ■■; ■ ■ ,'•'/■ .-. CONTR.OI^OF; A WIND STORM. For ,th«C larger :aerbplanes it will not be possible,: to include the-full span of the Yfiigs, s .bj*t4his, is;..unimportant. There;*s:oittle to *e/learned about the wings now, but-much to be learned ? bou* ithj^"isf?ect £ ,pti:air pressure pn the Jo^VPf^e wnigs,ithe fuselage; the tail^andrithV/enginel:;;-;. r ' xlt is, possible to walk through the ufnnel, and to inspect the remarkable eoncrete-^worfc —Across the-mouth of the collector^ 30ft in diameter a trellis of wire is stretched to stop any flying d6^^.:???. 1?? -being sucked against the fan. It,is interesting. to learn 'that it takes.:an extra.. 60 horse-power to make up for -this, ifee obstruction. The rotary, motion of the air caused by the fan is taken out' of the air stream by a system,- of str^ighteners behind the air-screw.; 'These- consist of a series of concrete pillars, one. side of which is flat. The^whirling air.-strikes the flat side and is straightened out. Then;the air stream has to be turned round two corners. If it were allowed :to ; find its own way round, eddies and disturbances would be set up which would interefere with accurate calculations. At each corner there are at series ■;■ of curved pillars close enough to one another to allow a man: to ;pass -sideways between two. By"this t tune .the tunnel grows wider and;Mgher, and' 'ttie backward course is through a chamber about 50ft .in height; so that, a 200 miles speed' at the riozzle jis; only 80.miles an hour through the. chamber. Once,more the air stream', has to .be ■ gjiided round semi-circular pillars and so back to the nozzle: -.-,■■ :', ;;,■■-■..-: ■• . ■ ~■:.-' Mrl.Pill, .acting as a [ demonstrator, was particularly proud of the accuracy of the construction.'. Concrete work was,:dpiie to' not more. than .an eighth of an inch iriaccuracy, and the centre of the nozzle was so nearly opposite the centre -of the fan that it would have cost a great deal dfinoney to pro- ' duce an-instrument to1 detect any inaccurafcy. ■•- - ■ .-r:-> /•./.■.- -■■■- ~ Roun4;the nozzle and the collector are perforations which lead' into de-tache-d, chambers. ■ Because of friction, the .air if "apt ; to be heated,.and if the engine\of th£:aeroplane' isf in'm'otion the ah-will'; become polluted. Through these perforations, therefore, fresh air may.be 4niroduced to .keep- an * even temperature "ami. to get rid ■ of. ■■ impurities. MEASURING MFT AND' DRAG. Ah aeroplane Jpr; testing is mounted on a frame. This frame is connected with an' lelabprate skeleton work en-, closed irt ; a chamber below. The skeleton work takes/the upward strain and the- drag independently, and these two pressures are registered on machines in another chamber where the operators,take..up-their station.- . The tunnel is capable of dealing with aircraft;of up; to,s6ft in span and COOOlb. in weijght.,.Full r scale tests in the tunnel;will-include -such investigations as cleanness of. design of the en-tu-e centre portion of ; the aircraft effect, on performance of possible improvements and alternative detail arrangement,, drag, and cooling of aircooled engines;—tests of radiator" systems, and schemes to improve the comfort of the crew. Opening;. .<he_.buildip4»,,,iord Londonderry sajd: "We a£a«here to inaugurate thei largest .'wßa-Hyiiiiel in this country;,and,onejpftbe^largest'in the world. Experience of the"information which can be extracted from models in,.smaller wind tunnels has led naturally to the expectation and hope _ that, by building a tunnel of sufficient size to carry out studies feom^the model; scale to full scale, we should haye a, most important instruwith which t0 extend IpSc^^w t^ c,? ontiers of our knowledgegn |he; field of aeronautics. We have,^fact, provided ourselves with ence-being that instead of sending our aeroplane up into the air we havf gg" 'ffie air down to i^ THE COST OF RESISTANCE. "I am told,;and I sincerely hope it is teue,that,if.we,can succeed by means of this \tunnel in reducing the resistance of aircraft, by one-tenth of its we should save n° less than £40,000 in the petrol bill of the Royal Air Force. I feel that the Treasury might welcome this modest addition

to future Budget surpluses. On the other hand, we could achieve substantially higher air speeds, with a corresponding increase in the fighting efficiency of the service. I will offer that prospect to those,who question the adequacy of our existing equipment. I am not prejudging the issue. I am only indicating the "amount of the prize money. "

. "We have aimed at equipping our research workers with a tunnel' capable of a large output of, work, and I am sure that it will meet.every demand likely to be made upon it for many years to come. The .tunnel has been under consideration arid . construction since 1928—for the thoughts of science, .like those of youth, are long.Tldng -arid, we; may have confidence that every care has been expended to make this the most serviceable and valuable . instrument for its purpose of which; the united skill and ingenuity of our mathematicians and scientists and constructors are capable." '■■■'/• IMPRISONED GENIUS. Before setting the giant ; fan ih motion Lord- Londonderry said: "It is now my duty to awaken the imprisoned genius of this place, and to start him, and 'those whom he> will serve, upon their labours for the benefit of aviation. . There is. much to be accomplished before,he will yield up all his- secrets; ;but, yield' them he shall, so that \ we-may- ride -him to* our greater safety: and outside in the space and freedom of his own element. May good attend, and success reward, the v/ork that is done within these waUs.'':i •::,;. . . I

The' Secretary of- State then pressed a button arid in the course of a minute the 30ft fan was revolving at high speed, the wind was leaping across the gap past a small fighting , aeroplane, but little or no breeze or draught was felt by those who sat within a few yards of the tornado-like air stream.