Tomographic particle image velocimetry
(TPIV) data were acquired in the logarithmic region of a zero pres-
sure gradient turbulent boundary layer ° ow at friction Reynolds number
Re¿ = 1160. Experiments were conducted in a suction type wind tunnel
seeded with olive oil particles of diameter »1¹m. The volume of interest
was illuminated by two Nd: YAG laser beams expanded with appropri-
ate optics into sheets of 8mm thickness in the wall-normal direction (z).
Images were acquired by four 2k x 2k pixel cameras, and correlation of
reconstructed ¯elds provided the full velocity gradient tensor in a vol-
ume of 0.7 ± x 0.7 ± x 0.07 ±, which resolved the region z + = 70-150 in
the log layer. Various vortex identi¯cation techniques, such as Galilean
decomposition and iso-surfaces of two- and three-dimensional swirl, were
utilized to visualize and analyze the eddy structures present in instanta-
neous ¯elds. The results of the present study will be compared to results
from earlier experimental studies that relied on planar PIV data only to
identify vortices and vortex packets as well as from a direct numerical
simulation of fully developed channel ° ow at comparable Re¿ .
(TPIV) data were acquired in the logarithmic region of a zero pres-
sure gradient turbulent boundary layer ° ow at friction Reynolds number
Re¿ = 1160. Experiments were conducted in a suction type wind tunnel
seeded with olive oil particles of diameter »1¹m. The volume of interest
was illuminated by two Nd: YAG laser beams expanded with appropri-
ate optics into sheets of 8mm thickness in the wall-normal direction (z).
Images were acquired by four 2k x 2k pixel cameras, and correlation of
reconstructed ¯elds provided the full velocity gradient tensor in a vol-
ume of 0.7 ± x 0.7 ± x 0.07 ±, which resolved the region z + = 70-150 in
the log layer. Various vortex identi¯cation techniques, such as Galilean
decomposition and iso-surfaces of two- and three-dimensional swirl, were
utilized to visualize and analyze the eddy structures present in instanta-
neous ¯elds. The results of the present study will be compared to results
from earlier experimental studies that relied on planar PIV data only to
identify vortices and vortex packets as well as from a direct numerical
simulation of fully developed channel ° ow at comparable Re¿ .
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