We study experimentally the power consumption P of a confined turbulent flow at constant Reynolds number Re. We analyze in details its temporal dynamics and statistical properties, in a setup that covers two decades in Reynolds numbers. We show that nontrivial power fluctuations occur over a wide range of amplitudes and that they involve coherent fluid motions over the entire system size. As a result, the power fluctuations do not result from averaging of independent subsystems and its probability density function $\Pi \mathrm{}\left(P\right)\mathrm{}$ is strongly non-Gaussian. The shape of $\Pi \mathrm{}\left(P\right)\mathrm{}$ is Reynolds number independant and we show that the relative intensity of fluctuations decreases very slowly as Re increases. These results are discussed in terms of an analaogy with critical phenomena.

• Received 28 September 1998

DOI:https://doi.org/10.1103/PhysRevE.60.R2452