280
R. A. ANTONIA AND R. E. LUXTON
' " ' 1 A . O n
to 1
( b )
% ' o
.'
A
W
.
":
0
0 0
10-3 r C O O 10'
5116' to' '
R*
FIG. 12. Frequency rpectra for smooth to r o w hterarl layer, normalired with T and 6,.
(a) w component; (b) uw. x& = 410: 0, rid, = 457; 0,O.M; A, 1.15. x/6, = 3.14:
a, 2 ~ 6 ,
= 0.67; A, 0.89.
concerned. This is substantiated by the t$,(k+) results of Figs. 9% 9b, and 1Oa
for z = 2.54 mm and a range of X stations. The &(k+) and t$,(k+) spectra
of Fig. 13 show surprisingly good collapse even at low wave numbers as does
the +,(k+) which is not shown here. A major dinirence between the smooth
to rough and the rough to smooth spectra is a substantial increase in the low
wave number part of t$,(k+) across the smooth to rough internal layer but
not across the rough to smooth internal layer. This is consistent with more
energetic diffusion in the smooth to rough case leading t o a more rapid
growth of the internal layer.