Coherent Wall Structures: Dynamics and Contribution to Turbulent Activity - Transport and Coherent Structures in Wall Turbulence - page 214

Figure 4.13. Ratio of contributions of ejections and sweeps
in the inner sublayer at . The solid spots represent
the results found by Kim et al. [KIM 87]

Re

τ =

500

The results achieved by various teams looking into the
contributions are in relative agreement in terms of the
logarithmic sublayer, irrespective of the Reynolds number
[WIL 72, WAL 72, LU 73, BRO 74, KIM 87]. However, there
are significant differences in the results found near to the
wall. The contributions of the QI and QIII interactions, for
example, are overestimated near to the wall in the
measurements recorded by Wallace et al. [WAL 72]. The
effect of the probe size, which becomes large when dealing
with large Reynolds numbers, can partially account for these
differences. The distributions of the ratio c II

c IV at different

Re values are relatively consistent.

The residence time T i , i.e. the percentage of time for which
( u , v ) is in the particular quadrant i , is defined by

IV
∑ , where N i is the number of events in Qi . The

T i = N i N i

i = I

residence times T II and T IV vary relatively little in the inner
sublayer (see Figure 4.14). The percentage of time accounted