282 Lecture 15 
Fig. 15.3. Transducer bank. 
8 
u 0) 
6 x A 
© 
z © 
% 4 
o 
Py © WILLIS 
[F © WILLIAMS 
2 X BULL 
4 WILLMARTH 
5 10 15 2-0 
Mach number (Free stream) 
Fig, 15.4. Over-all rms pressures. 
cps and below occurs, and this aspect is being further investigated. 
In view of the smallness of the pipe and our interest in pressure fluctuations 
at a point rather thanthe fluctuating loads over an area, Willis [2] at Southampton 
developed extremely small lead—zirconate—titanate pressure transducérs in a 
bank of twenty or more (Fig. 15.3) to determine the relative properties of the 
pressures at neighboring points. 
Figure 15.4 indicates the over-all pressure levels obtained in the various 
experiments. It is seen that both Willis [2] and Bull [1] agree very well with the 
