REYNOL.DS STRESS STRUCTURE IN TURHULENT BOUNDARY LAYER 305
1.0'
0. a
0
-
0
I
0. a
0.4
0. I
0.8
1.0
O L -
0
Y h
FIG. 16. Distribution of the ratio U'tiJ&.,
with H = 0, Re, -5 4230 (with permission of
J . Fluid Merh.).
one measurement for the high Reynolds number flow, it is conjectured that
the Reynolds number similarity may hold. This would imply that the nature
of the fluctuating turbulent structure in the wall region is similar above
Re, Y 4OOO but that at very low Re,, as in the work of Wallace et al. (1972),
significant changes in the structure of the turbulent fluctuations occur. It is
interesting to note that at higher Reynolds numbers in the present work, the .
contribution to U U during the burst period is larger than that found oy
Wallace et al. (1972). However, a word of caution is in order; it is possible
that significant measurement errors may be caused by operating hot wires or
FIG. 17. The ratio
with H = 0 as a function or y ' . 0. Re, = 4230; .,
Re,, 2 38,OOO; A channel flow (Wallace ef 01.. 1972). Re very low (with permission of J . Fluid
Merh.).