Flow field, turbulence and critical condition at a horizontal water intake.

This paper presents a study on the flow structure and turbulence characteristics of a horizontal water intake. The geometry is a basic configuration that is instrumental in the validation of experimental and numerical procedures, which could then be developed to a more complex geometry with more complicated flow patterns. Parallel to the experimental investigations, a three-dimensional numerical code for the prediction of any gravitational turbulent flow has been developed. This code assumes a flat free surface, but allows pressure contours over it. The three velocity components and their fluctuations at different water depths inside the intake bay are measured with a laser Doppler anemometer. This is then used to show the transition from the approach channel to the pipe and its importance on the flow structure and critical condition. A notable feature is that the streamwise component of the velocity in the channel accelerates from upstream to reach the pipe velocity in a length that is limited to twice the pipe diameter. The turbulence intensity is an index that identifies positions where free surface and subsurface vortices may form. Measurements and predictions are possible for the critical condition and its corresponding water level. The notable observation is that critical condition in this symmetric intake occurs with no swirl at the free surface. [ABSTRACT FROM AUTHOR]