Transition Length Between Water And Air-water
Flows On Stepped Chutes
Author(s)
A. L. A. Simões, H. E. Schulz & R. M. Porto
Abstract
This study presents the steps followed to obtain mathematical models for the
length of the transition region between the \“full-water” and \“full-mixed” flows in
stepped spillways. This transition length is defined here as the distance along the
flow, parallel to the pseudo-bottom, starting at the end of the \“full-water” region
and ending at the beginning of the \“full-mixed” region. The definition is
proposed based on experimental profiles of the surface obtained with an acoustic
sensor in a stepped chute, which allows one to locate adequately the minima and
maxima of the profile. A set of profiles obtained for different flow conditions is
shown, and a comparison between predicted and calculated transition lengths is
made. Experimental data and theoretical predictions superpose adequately for the
present set of data.
Keywords: air-water flow, aeration, transition length, stepped spillways.
1 Introduction
For the design of stepped chutes it is necessary to know the behaviour of the airwater
mixture along the flow. In many cases it is necessary to build bottom
aerators that must be conveniently placed, for which the position of the inception
point is needed (the section where the air begins to be captured by the water at
the upper surface). It is also necessary to know the length of the black water
region (upflow of the inception point), and the length along the flow needed for
the air to travel until the bottom of the channel (downflow of the inception
point). This length is here called \“transition length”, and is defined as the
Keywords
air-water flow, aeration, transition length, stepped spillways
Related Book
Other papers in this volume
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