37 
903 
CY. S)caty: 
er 4) ay 
NR and Ng are, of course, both positive. 
In (.02ng * .98), 
g (np - 1) 
Then, if g > 0.02, 
zy, when nm, 2 1. 
Hence 
(11.5) nR 2 n 
; R when n, 2 1. 
Np - 1 > eae oy Rn < 
By (11,1-4) 
Ba? Bs 
Hence, if a block must be of thickneee dp to satisfy (11,1), 
and of thickness dg to satisfy (11.2), 
(11.6) dg > dg. 
Turbulence 
12. The Reynolds number, R, corresponding to flow in a tube, is 
(72,3) R= vet 
where v #= velocity of flow, 
D = diameter of tube, 
Pp = density of fluid, 
/ = viscosity of fluid. 
The pressure difference necessary to maintain turbulent flow 
along a tube of length, s, is 
(12.2) Ap = As pz 
= 13 = 
