  Vortical structures of turbulence, i.e., vortex tubes and sheets, are studied
using one-dimensional velocity data obtained in laboratory experiments for duct
flows and boundary layers at microscale Reynolds numbers from 332 to 1934. We
study the mean velocity profile of intense vortical structures. The
contribution from vortex tubes is dominant. The radius scales with the
Kolmogorov length. The circulation velocity scales with the rms velocity
fluctuation. We also study the spatial distribution of intense vortical
structures. The distribution is self-similar over small scales and is random
over large scales. Since these features are independent of the microscale
Reynolds number and of the configuration for turbulence production, they appear
to be universal.
