July, 1929 AIRCRAFT ENGINEERIN G 179 [Unde r this heading will be published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee Report s and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodie s as issued.—Ed.] (Published by H.M. Stationery Office, London) The lift coefficient of the Blackburn wing R . & M . No. 1214 (Ae. 373). (December, (chord 9·1 8 in.) and of a R.A.F. 32 section wing R . & M . No. 1204 (Ae. 365). September, 1928. On a Metho d of Delaying the Opening (chord 3 in.) were measured behind three air 1928. Wind-Tunnel Experiments on the of a n Autoslot. (Wind Tunne l Experiments.) screws of 5·75 in. diameter, and the relative Desig n of an Automatic Slot for R.A.F. 34 By F. B. Bradfield and R. A. Fairthorne. positions of the wing and airscrews were Section . By F . B. Bradfield and F. W . G. (Price : 6d.) varied. Greener . (Price: 9d.) I n general, a n autoslo t which forms an efficient Th e increase in lift coefficient of the 3-in. slot at incidences near the stall will start to The tests form par t of a wind-tunnel investiga chord wing, centrally placed with regard to the open at too high a speed, thus increasing the tion of autoslots on wings of various sections. airscrews, is consistent with the assumption drag of the wing; and a method of delaying An aerofoil of R.A.F. 34 section has been tha t the lift of the portion of the wing in the th e opening is being sought. A model wing of tested with an auxiliary aerofoil whose chord is slipstream is increased in the ratio of th e square R.A.F.34 section fitted with an autoslot has 15 per cent. of the main chord. A range of of the slipstream velocity to the square of the been modified in such a way that, when the linkages was tested. The free position of the forward speed. The increase in lift coefficient slot is closed, the auxiliary aerofoil touches auxiliary and the lift of the wing when slotted of the 9·18-in. wing under similar conditions is th e main aerofoil a t its leading edge, but the along the whole span have been measured, and abou t half the amoun t which would b e estimated trailing edge is raised clear of the upper surface the drag was measured for one linkage. b y this method. of the main aerofoil. The free settings of the The maximum lift coefficient with the links When the 3-in. chord wing is close behind auxiliary aerofoil and the lift and drag of tested was 0·83. The slot opens too early, th e airscrews the lift coefficient is greater with th e wing have been measured. The opening of and the profile drag coefficient of a wing the airscrews above the wing; when the wing th e slot ma y be delayed by this means, but the slotted along the whole span rises a t k = 0·2 L is 8 in. behind the airscrew, it is greatest with slot will now close a t a higher speed tha n tha t at from 0·006 to 0·010. Forms of linkage which th e airscrew in line with the wing. which it opens. The opening is very sudden, give a later opening of the slot lead to impaired Some suggestions are made as to the effect and since the lift and drag alter as th e auxiliary control on the climb. of the inclination of the airscrew axis to the aerofoil opens, this may make flying at this Free settings, lift and drag, will be measured wind direction and the effect of the ratio of speed unpleasant. With one flap open and with the linkage modified, so tha t the trailing airscrew diameter to wing chord on the lift th e other closed, the aeroplane would be edge of the auxiliary aerofoil stands u p from the coefficient of th e wing in th e slipstream. seriously out of trim. Fabric sag, or badly- wing when the slot is closed. More systematic wind-tunnel tests are wanted fitted links, may give unintentionally a linkage to provide data on this subject. which is effectively of this type. R. & M . No. 1208 (Ae. 369). November, 1928. A Dash-Pot for use in Spinning R . & M . No. 1215 (Ae. 374). January, R . & M . No. 1209 (Ae. 362). November, Experiments on a Model Aerofoil. By T . H. 1929. The Accelerated Motion of a Cylin 1928. Wool-Tufts. A direct method of Fewster. (Price: 4d.) drical Body throug h a Fluid . By H . Glauert, discriminatin g between steady and turbulent Describes a dash-pot made to damp out the (Price : gd.) airflow over the wing surfaces of aircraft in oscillations in a balance for measuring the Fo r many purposes, it is convenient to flight : applied to explore the region of effect pitching or yawing moments produced on a represent the motion of a cylindrical body by of the slot on a Bristol Fighter wing. By model aerofoil due to continuous rotation about a suitable distribution of vorticity over its a rolling axis in a wind tunnel. It is thought Flight-Lieut . J. A. G . Haslam, D.F.C. , M.C . surface. The standard equations for the tha t a small dash-pot of this kind may be found (Price : 4d.) pressure distribution over the surface of a body useful for a variety of purposes. in accelerated motion have therefore been Describes a series of experiments made with converted into a form which involves only the tufts of wool sewn to strips of fabric doped on R . & M . No. 1212 (Ae. 371). November, first power of th e relative velocity or vorticit y on to the wing surfaces. By varying the positions 1928. Preliminary Tests on the Effect on th e surface, the only limitation on the analysis of the tufts and watching their behaviour in th e Lift of a Wing of the Position of the being that the circulation round the body is flight, it was possible to study the nature of Airscrew s Relative to It. By F . B. Bradfield. th e air-flow. In this way, the air-flow across constant in order that the flow shall remain (Price : 9d.) th e wings at and near the stall was explored. irrotational. The equations are applied to I n another experiment, the effect of the a n elliptic cylinder in accelerated motion and To explain the small measured increase in lift t o a straight line aerofoil describing a circular opening of the slot on the air-flow was coefficient due to the slipstream which was pat h with constant speed and angle of incidence. examined. found in model tests on a Blackburn Monoplane. 6 to 7·4 . The best result obtained, in the case The National Physical Laboratory of a body alone, was stated to be H E annual inspection of the National two bodies with radial engines slung side by These rings are so made that a section by an Physical Laboratory at Teddington took side, one being fitted with the Townend ring axial plane is that of an aerofoil working at Tplace on June 18, when all the Depart and the other not. By means of a botto m light, a high lift coefficient (tending to burst the ring ment s were thrown open to a large number of shadows of the models were thrown upwards outwards) and producing a downwash. This visitors. In the Aerodynamics Departmen t there and the fact optically demonstrated that the causes the flow to adhere to the body and so were displayed in th e various wind tunnel s exam ring caused a reduction of resistance in the reduces the turbulent wash in rear of the cylin ples of th e work tha t has been proceeding during order of 30 per cent. Further models and ders. th e pas t year. In th e large Duple x tunnel investi photographs showing the application of these Other research work demonstrated was that gations into change from laminar to turbulent rings in various shapes for the reduction of on wing and tail flutter, exploration of the flow in the boundary layer were demonstrated. resistance of radial air-cooled engines were boundary layer of an aerofoil by means of a The exploration was carried out by a hot wire, arranged on a table below the Duplex tunnel. small Pitot tube held from inside the aerofoil, and it was shown tha t the changes in th e current I n the case of a particular model of a complete and measurements of the effect of varying can not only be measured electrically, but can monoplane with a 9-cylinder engine, degrees of surface roughness on the drag of be rendered audible through amplification circular cylinders. The latest model of the into a loud-speaker. In the 7-foot No. 2 compressed air tunnel was also shown. tunne l was shown an extreme case of "inter ference effect" in connection with a general investigation that is proceeding into this was shown to be 0·7 3 subject. A stub wing was fitted below the nose Th e Parseval-Naat z Airship of an American stream-line airship shape, The German Parseval-Naatz 28 airship des tha t the ring produced 11 per cent. increase th e inter-action between wing and body being cribed in our last issue made a trial flight on of speed for a given horse-power. The overall so great that the combined drag was actually Jun e 6 at Seddin, remaining up for an hour negative and the body moved forward against during which she was thoroughly tested and is maximu m was a t the same time increased from th e air flow. The 7-foot No. 1 tunne l contained reported to have proved satisfactory.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: May 1, 1929