  For several flows of laboratory turbulence, we obtain long records of
velocity data. These records are divided into numerous segments. In each
segment, we calculate the mean rate of energy dissipation, the mean energy at
each scale, and the mean total energy. Their values fluctuate significantly
among the segments. The fluctuations are lognormal, if the segment length lies
within the range of large scales where the velocity correlations are weak but
not yet absent. Since the lognormality is observed regardless of the Reynolds
number and the configuration for turbulence production, it is expected to be
universal. The likely origin is some multiplicative stochastic process related
to interactions among scales through the energy transfer.
