Yeri Sutopo, FT Teknik Sipil and Budi S. Wignyosukarto, - and Bambang Yulistyanto, - and Istiarto, - Self and Artificial Air Entrainment in Steep Channel. In: The 5th International Conference of Euro Asia Civil Engineering Forum (EACEF-5), 15-18 September 2015, Surabaya.

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Abstract

High flow velocity causes a low pressure even negative, especially in steep channel bed. Force caused by negative pressure will lift the bed surface and side walls of the building hydraulic structures, which can lead to flaking on the bed surface and side walls of the building. In supercritical flow, air from the atmosphere enters into the body even reach the bed flow. Air entrainment enters into the body and bed flow can prevent or reduce the phenomenon of cavitation in channels bed. The purposes of this study were: (a) describe concentration distribution of air bubbles in the developing regions of the self air entrainment; (b) describe concentration distribution of air bubbles in the artificial air entrainment; and (c) aerator effectiveness test in increasing air bubble concentration in the steep channel bed. Three purposes of research were achieved using experimental methods implemented in the Hydraulics Laboratory of the Department of Civil and Environmental Engineering (JTSL), Faculty of Engineering, Gadjah Mada University (UGM). In this study, the steep channel having a length of 10 m, width 0.2 m, height 0.4 m with slope varies from 20º, and 25º, which was fused with the wall of the water tank. Discharge was 20.9 l/s. The conclusion of this research were: (a) the concentration distribution of air bubbles on the condition of self-air entrainment in slope channel bed 25º and discharge=20.9 l/s can be predicted using the results of the calculation equation Straub and Anderson (1958) modification; (b) the concentration distribution of artificial air entrainment on the slope of the channel bed=25º at a point 7.2 m from the inlet flume and in the free surface aeration, was the Gaussian or normal, and (c) on the slope of the channel bed=25°, at a point 7.2 m from the inlet flume on the condition of artificial air entrainment in the downstream flow region after the first aerator installed a new aerator is not required anymore.

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