  Turbulent flow fields can be expanded into a series in a set of basic
functions. The terms of such series are often called modes. A master- (or
determining) mode set is a subset of these modes, the time history of which
uniquely determines the time history of the entire turbulent flow provided that
this flow is developed. In the present work the existence of the
master-mode-set is demonstrated numerically for turbulent channel flow. The
minimal size of a master-mode set and the rate of the process of the recovery
of the entire flow from the master-mode set history are estimated. The velocity
field corresponding to the minimal master-mode set is found to be a good
approximation for mean velocity in the entire flow field. Mean characteristics
involving velocity derivatives deviate in a very close vicinity to the wall,
while master-mode two-point correlations exhibit unrealistic oscillations. This
can be improved by using a larger than minimal master-mode set. The near-wall
streaks are found to be contained in the velocity field corresponding to the
minimal master-mode set, and the same is true at least for the large-scale part
of the longitudinal vorticity structure. A database containing the time history
of a master-mode set is demonstrated to be an efficient tool for investigating
rare events in turbulent flows. In particular, a travelling-wave-like object
was identified on the basis of the analysis of the database. Two
master-mode-set databases of the time history of a turbulent channel flow are
made available online at http://www.dnsdata.afm.ses.soton.ac.uk/. The services
provided include the facility for the code uploaded by a user to be run on the
server with an access to the data.
