NO. 4 PIONEER WIND TUNNELS RANDERS-PEHRSON 9 



The speed of the air at any point was indicated by the undulations 

 of the smoke bands caused by these vibrations. Judging from some 

 of the photographs where the measuring rod is seen, the speed was 

 about 30 centimeters per second. 



A number of very beautiful flow photographs were obtained by 

 Dr. Marey." 



A. F. ZAHM 



The first complete wind-tunnel laboratory, equipped for a wide 

 range of aerodynamical experiments and with instruments capable 

 of exact measurements, was devised by Dr. A. F. Zahm and erected 

 on the grounds of the Catholic University of America in the winter 

 of 1901. 



This laboratory was made possible by Hugo MattuUath, inventor 

 of a giant flying boat. Dr. Zahm having agreed to become, during his 

 spare time, the consulting engineer of Mattullath's company. 



The laboratory building was a one-story frame structure 30 by 80 

 feet and housed a wooden tunnel 6 feet square in cross-section and 

 40 feet long, with windows in the ceiling and walls. The wind was 

 drawn through at a speed of 27 miles per hour by a 5-foot suction 

 fan, driven by a 12 hp. electric motor. The intake end was covered 

 with one or two screens of cheese cloth or wire mesh to straighten 

 the wind. The air speed was held constant within a fraction of i per- 

 cent by a boy with a tachometer and a rheostat, controlling the fan 

 speed. For some researches movable liners were introduced in the 

 main tunnel, making the current contract trumpetwise to gain speed, 

 then run straight in a narrower stream, and finally discharge as an 

 open jet in the after part of the main tunnel. The testing model was 

 placed either between the parallel sides, where the wind speed was 

 greatest, or in the center of the current where it entered the experi- 

 mental chamber. 



The wind tunnel was equipped with a variety of instruments in- 

 vented by Dr. Zahm for showing the character of the air flow and 

 its action on the models. 



" C. R. Acad. Sci., vol. 131, pp. 160-163, July 16, 1900; vol. 132, pp. 1291- 

 1296, June 3, 1901. 



Ann. Rep. Smithsonian Inst., 1901, pp. 14, 332, 337-340, pis., 1902. 



Journ. phys. theroique et appliquee, 4th ser., vol. i, pp. 129-135, illus., 1902. 



Scientific American, n. s., vol. 86, pp. 75-76, illus., Feb. i, 1902. 



Nogues, P., Recherches experimentales de Marey sur le mouvement dans 

 I'air. France. Min. de I'air. Publ. sci. et techn., pp. 94-97, illus., 1933. 



