NO. 4 



WIND TUNNEL EXPERIMENTS IN AERODYNAMICS 



33 



the static pressure. The arrangement of the holes appeared to have 

 no effect. Long- slots in the tube introduced large errors if the tube 

 were not pointed fair into the wind. The size of the tube appeared 

 to be immaterial. 



The results of comparison of three tubes with different arrange- 

 ments of holes from 4 to 24 in number are shown on figure 6. The 

 tubes are shown on figures 3, 4, and 5. The agreement is very close- 

 within ^ per cent at velocities above 10 miles per hour. 



Fig. 7. — Effect of inclining Pitot tubes to wind. 



Tests were made to determine the effect of inclining the tubes to 

 the wind. The tubes with holes show an error of but i per cent for 

 an inclination of 4 degrees. The results are shown on figure 7. 



The following conclusions may be drawn from these tests : 



( 1 ) Static openings should be small holes about 0.03 inch in diam- 

 eter to minimize effects of bad alignment or turbulence. 



(2) An error of 2 degrees in aligning the tube causes no impor- 

 tant change in velocity reading. 



(3) If a tube is correct at two speeds it remains correct at all 

 others within the range of our experiments. 



