Approximation of velocity distribution in open channel flow

Abstract eng:
The paper deals with approximation of spatial distribution of mean downstream velocity of sub-critical turbulent flow in an open rectangular channel with rough bed. New formulae of the local downstream velocity component Vx(y, z) dependence on the vertical coordinate y and lateral coordinate z were introduced. The vertical velocity profile was approximated by log-law and the power law was used to describe the effect of channel walls on the horizontal velocity profile. The suggested formulae of spatial downstream velocity component distribution were calibrated and verified using the experimental data obtained by PIV method. The proposed approximation is in good agreement with experimental data, the difference between experimental and calculated data is in range of 5 - 10% except the area near the channel’s corners and water level, where the maximal difference reaches 60% and 30% of experimental values, respectively. Introduction A velocity distribution of one-dimensional flow in open channels is traditionally described by a log-law or by a power law. The log-law and the power law can be used not only for vertical velocity distribution, but also for a lateral distribution of local velocity. In this paper we shall suppose that the spatial velocity distribution can be approximated by the log-law for the vertical velocity profile and by the power law for the horizontal velocity profile and for the description of the channel walls effect. A logarithmic law and power-law (see, e.g. Schlichting, 1979): u=

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