The influence of self-aeration on resistance in smooth and rough steep channels

• DOI: 10.1007/bf01560459
• Publication Date: 2005-04-27T19:30:36Z
• Authors: Antonio Petrillo; Matteo Ranieri
• Keywords: Froude number; Flow resistance

Flow resistance was examined in a wide rectangular channel with the bed sloping between 4° and 12°. The working hypothesis was that a uniform flow occurs in the resulting self-aerated stream at the gauging section. Analysis of data taken in the channel, both with a smooth and rough bottom, showed that in the portion of the stream formed essentially by water - and for which wall stress was calculated by assuming depth h05, where air concentration is 5%, as significant - the resistence index can be calculated with the laws applicable to pipes without any need to use the shape factor. The experimental relationship that relates Froude's number of the stream to depth h05 was used to calculate the hydraulic proportions of the channel. The overall characteristics δh and δq of the aerated layer are given. The paper shows that these characteristics depend on turbulence in the water layer and on discharge.