3 research outputs found
Rough-conduit flows and the existence of fully developed turbulence
It is widely believed that at high Reynolds number (Re) all turbulent flows
approach a state of "fully developed turbulence" defined by a unique,
Re-independent statistics of the velocity fluctuations. Yet direct measurements
of the velocity fluctuations have failed to yield clear-cut empirical evidence
of the existence of fully developed turbulence. Here we relate the friction
coefficient () of rough-conduit flows to the statistics of the velocity
fluctuations. In light of experimental measurements of , our results yield
unequivocal evidence of the existence of fully developed turbulence.Comment: 5 pages, 2 figure
Turbulent Friction in Rough Pipes and the Energy Spectrum of the Phenomenological Theory
The classical experiments on turbulent friction in rough pipes were performed
by J. Nikuradse in the 1930's. Seventy years later, they continue to defy
theory. Here we model Nikuradse's experiments using the phenomenological theory
of Kolmog\'orov, a theory that is widely thought to be applicable only to
highly idealized flows. Our results include both the empirical scalings of
Blasius and Strickler, and are otherwise in minute qualitative agreement with
the experiments; they suggest that the phenomenological theory may be relevant
to other flows of practical interest; and they unveil the existence of close
ties between two milestones of experimental and theoretical turbulence.Comment: Accepted for publication in PRL; 4 pages, 4 figures; revised versio