February 20, 19 13] 



NATURE 



EXPERIMENTAL STUDIES IN AERO- 

 DYNAMICS.^ 



M EIFFEL has contributed much to the 

 experimental study of aerodynamics and 

 aeronautics, and his experiments at the Eiffel 

 Tower some years ago upon air resistance at high 

 velocities will be recalled as establishing the truth 

 of the squared law for velocities up to 40 metres 

 a second. His subsequent researches at his 

 laboratory in the Champ de Mars will be familiar 

 to all students of the subject, and more particularly 

 to those concerned with the more practical aspects 

 of aerodynamics as pertaining to the design of 

 aeroplanes. In this paper he describes some recent 

 researches, and also the apparatus and equipment 

 at his new laboratory in the Rue Boileau, Auteuil, 

 which the writer has had the opportunity of 

 inspecting, thanks 

 to the courte.sy of 

 M. Eiffel and of 

 M. Rith, his able 

 collaborator. 



This laboratorv 

 was designed on a 

 more extensive 

 scale than that of 

 the Champ de 

 Mars, for the wind 

 tunnel in the latter 

 only allowed velo- 

 cities of j8 metres 

 a second. As the 

 speed of aero- 

 planes consider- 

 ably exceeds this, 

 it was deemed ad- 

 visable to con- 

 struct new appara- 

 tus to obtain velo- 

 cities more nearlv 

 those attained in 

 actual flight. The 

 large wind tunnel 

 in this laboratory 

 consists of a tube 

 provided with a 

 fan, the tube 



being made on the Venturi pattern, and in 

 that part corresponding to the "throat" is 

 situated the room containing the delicate register- 

 ing apparatus, in which the attendants can watch 

 and work the tests upon aerofoils of large size 

 suspended in the current (Fig. i). The current 

 traverses this room, the outlet and inlet being on 

 opposite sides. The cone collector has diameters 

 of 4 and 2 metres with a length of 330 metres, 

 and the diffuser (or discharge end of the tube) has 

 a length of 9 metres and ends with a fan 4 metres 

 in diameter (Fig. 2). With this large tunnel veloci- 

 ties of 2 to 32 metres per second are obtained. 



Parallel with this tube, and passing through 



the same instrument or measuring room, is 

 another, i metre in diameter, by which velocities 

 of 40 metres per second (89 miles per hour) can 

 be obtained. The registering apparatus is carried 

 upon a chariot running on rails, and may be moved 

 from one tube to the other, as desired, across 

 the instrument room. So much for the design 

 of this laboratory, at present the largest of its 

 kind in existence, and very complete in all that 

 pertains to experimental aerodynamics. 



The first tests made at the Auteuil laboratory 

 and described in the paper before us were upon 

 model aeroplanes to determine, if possible, the 

 laws of similitude between an aeroplane and its 

 model. For this purpose an exact model, con- 

 structed to a scale of i to i4'5, was made of the 

 aeroplane used by Col. Bouttieaux and M. Meudon, 

 of the militarv aeronautical laboratorv at Chalais- 



TAviation faites aux lah 

 M. G. Eiffel. Exirait d 

 France. (Bulletin de Ju 



i et d'Ante 

 Ing^nieuri 



Meudon, for experimental purposes and equipped 

 with registering apparatus. By pressing a button 

 the pilot, Lieut. Saunier, when flying on an abso- 

 lutely calm day, could register photographically 

 the following data: — (i) the kinetic thrust of the 

 propeller, or head resistance, usually called 

 " drift " ; (2) the speed of the propeller ; (3) the 

 velocity of the aeroplane relative to still air ; (4) 

 the angle of attack or angle made by the chord 

 of the aerofoils with the line of flight. 



The model of this aeroplane was subjected to 

 tests in the laboratory at velocities about the same 

 as those of the actual flight, and curves were 

 drawn giving the values of lift and drift for 

 different angles of attack. When these resist- 

 ances, horizontal and vertical, are compared for 

 the aeroplane and its model, they are found to 



NO. 2260, VOL. 90] 



