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Aviation History
1925
1925 - 0020.PDF
TESTS OF ROTATING CYLINDERS : The upper photograph, Fig. 15, shows the streamlines at 600 r.pon. In the centre, Fig. 16, they are shown at 1,200 r.p.m. and in Fig. 17 at 2,400 r.p.m. The air- speed in all three cases was 5 metres per second. JANUARY 8, 1925 very limited range. The slopes of the curves of Ccw vs. r are much lower than the preceding ones, even though the coefficients were computed on the basis of projected area of the cylinder rather than the transverse projection of the strut. As regards L/D ratio, the smaller gap is best, and it is felt that if it had been possible to use still smaller clearance and practically eliminate any flow through the gap, much better results might have been realised. It is evident that with any appreciable gap, the circulation around the entire assembly is reduced by the flow between the cylinder and fairing. It will be seen that lift appears at the smallest values of r observed. . . , Conclusions • » The controlled combination of translational and circulatory velocities has shown that:— 1. The air forces obtainable by superposition of a circula- tory flow upon the one arising from translation of a doubly symmetric body are several times greater than have ever been observed on any unsymmetric body. 2. Lift increases with circulation, although the law con- necting the variables is not definitely established or its limits of application known. 3. The rate of increase of lift with rate of revolution seems practically independent of the shape of the rotating body, provided it is symmetrical about both axes in its plane of rotation, except at the very low speeds. 4. The drag of a blunt body in rectilinear air flow may be considerably reduced by the addition of a circulatory flow. (It seems probable that this results in a reduction in the width of the turbulent area behind the cylinder before any " downwash " or change in the direction of the discharged airstream appears. This is in accord with the Karman theory of resistance as given in Joukowski's " Aerodyna- mique." p. 203). Bibliography Reference 1.—Technical Report No. 116: Applications of Modern Hydrodynamics to Aeronautics. By L. Prandtl. 1921. Certain experiments have been carried out at the Dutch experimental laboratory on an aerofoil into the leading edge of which was fitted a cylinder. Tests were carried out with the gap between cylinder and wing closed and open, and with the cylinder stationary and rotating at various speeds. It was found that a very considerable increase in lift coeffi- cient could be obtained in this way. Next week we hope to publish a brief resume of the Dutch experiments.—ED. •jf New Year Honours AMONG the names mentioned in the New Year Honours list the two following are of special interest in connection with aviation : Knights Bachelor : Alfred Henry Ashbolt, Esq. Royal Victorian Order, G.C.V.O. : TheRt. Hon. Weetman Dickinson, Viscount Cowdray. The former was lately Agent-General in London for Tasmania, and took a keen interest in the question of an airship service from England to the various Colonies. Viscount Cowdray will be remembered as being the first Air Minister in the world, it being in January, 1917, on the occasion of the reconstruction of the Air Board, that this office was created and filled by Viscount Cowdray. The Home Defence Air Force ON January 1, Britain's new Home Defence Air Force officially came into existence, and Air-Marshal Sir John Salmond took up the appointment of Chief of this new Force. There are at present some 18 defence squadrons in existence, and this number will be increased to 52 squadrons. A Gordon Bennett Balloon Race this Year A SECOND Gordon Bennett Cup for balloons has been definitely decided upon by the Belgian Aero Club, and will be competed for on June 7, starting at Brussels. German Low-powered Aeroplane Competitions DURING 1925 some 300,000 marks will be offered as prizes for low-powered aeroplane competitions in Germany. The competitions will be divided into three classes—for aeroplanes fitted with engines of 40 h.p., 80 h.p., and 120 h.p., respectively, while the prizes will be made up of the following : The Otto Lilienthal (105,000 marks) ; the " B.Z. " (100,000 marks) ; the Boelcke (50,000 marks) ; and the Richthoven (45,000 marks). In the " B.Z. " section machines will have to make five circular tours in Germany of from 120 to 750 miles, and extending over a period of ten days. An American Transatlantic Airship Co. WITH the object of operating transatlantic airship services between Boston and London, and Boston and San Francisco, a commercial airship company, with a capital of $50,000,000 (£10,000,000) is being formed in Boston. It is proposed to build twenty airships, each capable of carrying about 100 passengers and 50 tons of freight, and the passenger tariffs will be the same as the present steamship and rail fares. Pulham Station to Re-open PREPARATIONS are being made to reopen Pulham Airship Station, where the R.33 is expected to arrive next month. The R.33 will carry out tests here with the 100 ft. steel mooring mast. •: • The American World-Flight THE U.S. Secretary of War has approved the plan of the War Department to advance Captain Lowell H. Smith, who led the American World-Flight, 1,000 files on the promotion list, and Lieutenants Wade, Nelson, and Arnold 500 files each. For Captain Smith the advancement is equal to 13 years' service, and for the others four years' service. The increases in seniority become effective after they have been approved by the President and Congress. Mr. Austin Chamberlain received the following message from the U.S. Ambassador in London :—Under instructions from my Government, I have the honour to express the deep apprecia- tion of the American Government for the many courtesies and assistance extended by the British authorities to the American aviators in their recent flight around the world. The American Government fully realises that without the co-operation of the various foreign Governments over whose territory the flight passed this achievement would not have been possible, and it is, therefore, particularly happy to express its gratitude to H4s Majesty's Government for its cordial co-operation. 20 .._,-•".•
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