164 



SYMPOSIUM ON AERONAUTICS. 



hill has followed him in working- out a great number of cases with 

 great skill. In Fig. 3 we see the flow past a camibered wing, with 

 stream-lines continuous in Fig. a, causing no pressure, and in Fig. h 

 with the stream splitting along the dotted line, part going up and 



Fig. 3(7. 



part down, with discontinuity along the lines AB, CD, between 

 which the fluid is comparatively at rest. From this assumption of 

 the flow it is possible to calculate the thrust and the turning. But 

 even this assumption about the flow is not true in practice, but 

 the air forms vortices, wdiich cause a calculation to be still more 



Fig. 2)^. 



difficult. Accordingly it becomes necessary to determine the laws 

 of pressure by actual experiments on small scale models in wind 

 tunnels, such as those of M. Eifi^el in Paris, Professor Prandtl in 

 Gottingen, Professor Joukowsky in Moscow, or that at the Massa- 

 chusetts Institute of Technology used by Mr. Hunsaker in his ex- 

 periments. In all these cases a steady stream of air is caused to 

 flow through the tunnel by means of a blower, and the model is 

 hung in the w^ind upon balances which enable the forces, their 

 points of application and direction to be carefully measured for all 

 angles of attack. We may expect in the next few years to see many 

 such wind-tunnels constructed in this country, and large increases 

 made in our experimental knowledge. 



