  The elementary structures of turbulence, i.e., vortex tubes, are studied
using velocity data obtained in laboratory experiments for boundary layers and
duct flows at microscale Reynolds numbers 332-1934. While past experimental
studies focused on intense vortex tubes, the present study focuses on all
vortex tubes with various intensities. We obtain the mean velocity profile. The
radius scales with the Kolmogorov length. The circulation velocity scales with
the Kolmogorov velocity, in contrast to the case of intense vortex tubes alone
where the circulation velocity scales with the rms velocity fluctuation. Since
these scaling laws are independent of the configuration for turbulence
production, they appear to be universal at high Reynolds numbers.
