"resonance coefficient" and "substitution" methods, the author describes an instrument for the measure ment of the loss angle for frequencies up to 10 mega cycles per second. This instrument consists essentially of a radio frequency generator, an oscillator, a valve Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical voltmeter and a coupling device, the function of which Research Council, Reports and Technical Notes of the United States National Advisory Committee is explained. for Aeronautics and publications of other similar Research Bodies as issued. A system for obtaining standard conditions with controlled temperature and humidity was developed in connexion with this work. GREAT BRITAIN HE British Research Reports and Memoranda, The results of tests on low-loss ceramic materials, summaries of which appear below, are the first AERONAUTICAL RESEARCH COUNCIL conducted with this apparatus at Guidonia, are to be described as reports of the Aeronautical H.M. Stationery Office, London included. Research Council. The change of title, from Aero R. &M. No. 1993. The Effect of Openings on the nautical Research Committee, was announced by Sir Nos. 53-54. I Laboratori di Guidonia per le Prove Stafford Cripps, then Minister of Aircraft Production, Torsional Stiffness of Rectangular Section Tubes. di Resistenza dei Materiali. (The Laboratories at in the House of Commons on April 11, 1945, in the January, 1939. By H . J. Allwright. (2s.) Guidonia for Testing the Strength of Materials.) By following terms: It has been shown by Williams that holes or gaps in G. Montelucci. the cover skin of a stressed-skin wing may cause The Aeronautical Research Committee will, as After considering the criteria on which the organi considerably increased stresses; it was desired to from April 1, be known as the Aeronautical Research zation of the research was based, the author describes obtain quantitative information on the corresponding Council. The Council will consist of 14 members, of the group of laboratories concerned with the mechani reduction in torsional stiffness. whom eight (including the Chairman) will be non- cal and technological investigation of the materials Following the analysis given by Williams, an official members. used in aircraft construction. The laboratories include expression is derived for the torsional stiffness of a Following are the terms of reference and names of those for static tests, fatigue tests, for testing textiles, rectangular section tube with an opening through the the members: wood and rubber, for testing building materials, and upper and lower cover skins, when a concentrated 1. To advise the Minister responsible on scientific problems for testing hydraulic systems under pressure. torque is applied at an intermediate section outboard relating to aeronautics. 2. To keep under review the progress of aeronautical research of the opening. This stiffness is compared with the and to advise the Minister on the programme and the planning of stiffness of a similar tube with no opening, and the aeronautical research carried out for the Government of the effects of varying the length and position of the United Kingdom. 3. From time to time, to make recommendations to the Minister opening and of varying the flange area of the spars arc on research which the Council considers it desirable to initiate. examined for a torque applied at the three-quarter 4. When requested to do so, to tender advice upon any research span section. carried out by or on behalf of the aeronautical industry. 5. Subject to the needs of security, to make the results of Openings such as are necessary for fuel tanks and British research generally available, by the publication of research retractable undercarriages may cause serious losses reports. of torsional stiffness, and should bo made as short as 6. To advise upon aeronautical education in the United King dom in so far as it is relevant to research. possible in a spanwise direction. An opening of given 7. To maintain contact with similar bodies or institutions in the dimensions results in least loss of stiffness when very Dominions and foreign countries. near the wing root, but it then causes larger local 8. To make an annual report to the Minister. stresses than if positioned out along the span. Increase Non-Official Members of spar flange area above that necessary for flexural Sir Melvill Jones, C.B.E., A.F.C., M.A., F.R.S., F.R.Ae.S. strength has little effect in reducing the loss of torsional (Chairman).Professor L. Bairstow, C.B.E., D.Sc., F.R.S. , F.R.Ae.S. Dr. D. R. Pye,C.B,,M.A.,Sc.D.,M.I.Mcch.E.,F.R.S., F.R.Ae.S. stiffness. Sir William Stanier, M.I.Mech.E. Sir Geoffrey Taylor, M.A., F.R.S. Dr. II. Roxbee-Cox, F.R.Ae.S., D.I.C. Dr. S. Goldstein, No. 2001. The Supersonic Theory of Wings of M.A., F.R.S. Dr. A. G. Pugsley, O.B.E., A.M.I.Struct.E., Finite Span. October 2, 1944. By M . J . Lighthill. (3s.) A.F.R.Ae.S. Using the previous work of Schlichting, but work Official ing from rather a different point of view, a general Director of Scientific Research, Admiralty. Representatives of the Department of Scientific and Industrial Research and of the theory of wings of finite span, whose cross-section is National Physical Laboratory. Director-General of Scientitic constant along the span, is set out. Opportunity is Research and Development, Ministry of Supply. Director of the taken to outline all developments of the supersonic Royal Aircraft Establishment. Director of Scientific Research, Ministry of Aircraft Production. theory, along the lines of the "linearized equation", which have hitherto been made. Every effort has been shape. The pressure at any point on the outer and made to clarify the physical and mathematical bases inner surface is calculated in terms of the shape, and of the theory. hence the drag is known. Other points about the flow It is found that, for a rectangular wing of aspect arc discussed. ratio A, at Mach number M the effective angle of Finally a discussion of bodies at yaw is carried out, incidence is reduced by a factor, which is given, following the work of Tsien. For a shell the lift but there is no induced drag. coefficient is 2 per radian of yaw angle; the centre of For a wing of trapezoidal plan, the longer side pressure is also found. For a body pointed at both facing the stream, there would be no change in lift or ends, there is no lift but only a pure couple pV2ψT drag for sufficiently high Mach numbers: they would (ψ the yaw angle; T the volume of the body) tending be the same (related to the wing area) as for two- to increase the angle of yaw. dimensional flow. However, this modification may not be worth making in practice, seeing that the reduction-factor mentioned above is so little less than ITALY unity. ATTI DI GUIDONIA Direzione delle Cortruzione Aeronautiche Ufficiostudi R. & M . No. 2003. Supersonic Flow Past Bodies of Ministero del' Aeronautica, Rome Revolution. January 3, 1945. By M. J. Lighthill. (4s. 6d.) Nos. 49-50. Esperienze su Famiglie di Eliche Multi- This paper is a development of the work of Kármán pale. (Experiments with Families of Multi-Blade Air and Moore. For slender bodies of revolution pointed screws.) By A. Eula. at both ends, the slope of whose meridian section is With the object of investigating the advisability of continuous, a theory is developed which gives the adopting airscrews of more than four blades, experi velocity distribution over the whole field correct to ments have been conducted on families of airscrews of the first and second orders in the thickness of the body, two, three, four, five and six blades over a large range when it is placed in a uniform supersonic stream of blade angles and advance-diameter ratios. The tests flowing in the direction of its axis. The asymptotic were made in the 2-metre open-jet wind tunnel, hav value of the drag as the thickness tends to zero is ing a maximum velocity of 70 metres per second and found to be a turbulence factor of 1•25. The results are examined critically, compared with results of similar experi ments in other countries, including those at the N.P.L., and their applicability is discussed. Although where S(x) is the cross-sectional area of the body at a the research was not exhaustive, because the blades distance x along its length. The drag coefficient is thus were the same, only their number being varied, and be independent of Mach number to this approximation, cause the effect of the high tip-speeds was not taken and varies as the square of the fineness ratio (so that into account, the conclusion was reached that the for a given length the drag itself varies as the fourth adoption of airscrews of more than four blades may be power of the thickness). Possible limitations are advantageous in the case of power units of very great indicated. power at great altitudes and at great velocities. This The theory also holds for shells (if their noses are advantage could not, however, be estimated quantita fairly sharp) in the region ahead of the base, and (1) tively without further research. gives the correct expression for the wave drag (as Nos. 51-52. Sulla Misura a Radiofrequenza dell' distinct from the base drag and friction drags). Angolo di Perdita dei Materiali Isolanti Dielettrici. For both pointed bodies and shells, the minimum (On the Measurement by Means of Radio Frequency of wave drag is found (for given fineness ratio), and the Dielectric Loss Angle of Insulating Materials.) practical shapes with drag coefficients near to the By F . Bocci. theoretical optimum are in both cases given. After giving some general notes on methods of A theory is then worked out for supersonic flow in measuring the dielectric loss angle, and explaining the and around open tubes of approximately cylindrical 378 Aircraft Engineering
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Nov 1, 1946
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