Finite lifetime of turbulence in shear flows

Bjorn Hof, Björn Hof, Jerry Westerweel, Tobias M. Schneider, Bruno Eckhardt

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Generally, the motion of fluids is smooth and laminar at low speeds but becomes highly disordered and turbulent as the velocity increases. The transition from laminar to turbulent flow can involve a sequence of instabilities in which the system realizes progressively more complicated states, or it can occur suddenly. Once the transition has taken place, it is generally assumed that, under steady conditions, the turbulent state will persist indefinitely. The flow of a fluid down a straight pipe provides a ubiquitous example of a shear flow undergoing a sudden transition from laminar to turbulent motion. Extensive calculations and experimental studies have shown that, at relatively low flow rates, turbulence in pipes is transient, and is characterized by an exponential distribution of lifetimes. They also suggest that for Reynolds numbers exceeding a critical value the lifetime diverges (that is, becomes infinitely large), marking a change from transient to persistent turbulence. Here we present experimental data and numerical calculations covering more than two decades of lifetimes, showing that the lifetime does not in fact diverge but rather increases exponentially with the Reynolds number. This implies that turbulence in pipes is only a transient event (contrary to the commonly accepted view), and that the turbulent and laminar states remain dynamically connected, suggesting avenues for turbulence control. © 2006 Nature Publishing Group.
    Original languageEnglish
    Pages (from-to)59-62
    Number of pages3
    JournalNature
    Volume443
    Issue number7107
    DOIs
    Publication statusPublished - 7 Sept 2006

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