Author(s): P. Y. Julien; D. M. Hartley

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Abstract: The formation of'a series of roll waves in laminar sheet flows in a smooth channel is examined both theoretically and experimentally. Roll waves were observed in subcritical flows at a Froude number as low as 0.74. The recommended theoretical relationship for the celerity of roll waves is a function of the momentum correction factor. This relationship is in good agreement with measured celerities of roll waves. The period of roll waves remained fairly constant throughout these experiments. Previous derivations of the length required for the formation of roll wave were modified because experimental evidence demonstrates that the simplified relationship for the celerity of roll waves does not hold true for laminar sheet flows. Using the modified relationship, the dimcnsionless distance displays an hyperbolic variation with the Froude number and good agreement is obtained with experimental data. This analysis also demonstrates that for supercritical flows the distance is proportional to the ratio of flow depth and slope. Alternatively an equivalent function of Reynolds number and slope can be used.

DOI: https://doi.org/10.1080/00221688609499329

Year: 1986