a1 Department of Engineering, Cambridge University, Trumpington Street, Cambridge CB2 1PZ, UK
Three-dimensional (3D) measurements of a turbulent boundary layer have been made using high-speed particle image velocimetry (PIV) coupled with Taylor's hypothesis, with the objective of characterising the very long streamwise structures that have been observed previously. The measurements show the 3D character of both low- and high-speed structures over very long volumes. The statistics of these structures are considered, as is their relationship to the important turbulence quantities. In particular, the length of the structures and their wall-normal extent have been considered and their relationship to the other components of the velocity fluctuations and the instantaneous stress.
(Received April 08 2010)
(Revised September 27 2010)
(Accepted December 03 2010)
(Online publication March 14 2011)