AN EXPERIMENTAL AND NUMERICAL STUDY OF FLOW PATTERNS AT A 30 DEGREE WATER INTAKE FROM TRAPEZOIDAL AND RECTANGULAR CHANNELS

Abstract

Knowing flow pattern, especially stream tube dimensions at the vicinity of a lateralintake is important to study flow discharge and sediment rate entering to the intake as well as tobetter design a measure for controlling sediment entry into the intake. Previous studies have beenfocused on intake from rectangular channels. In the present study, however, different experimentaltests were carried out at a 30 degree water intake installed at bank of a trapezoidal channel tomeasure the three components of flow velocities; these data were then applied to calibrate thenumerical SSIIM2 model; by running the SSIIM2 model for different flow conditions, more datawere obtained. From the analysis of both experimental and numerical data the flow patternsupstream of intake were plotted and the stream tube dimensions were obtained for all flowconditions. It was found that the dividing stream width for intake from trapezoidal canal at thebottom is less than it is for intake from rectangular canal for the same flow conditions; the width atany elevation was found to depend directly on the diversion flow ratio. Relations for predictingdividing stream width as a function of diversion flow ratio have been presented for intake fromboth rectangular and trapezoidal cross sections. Also, computed secondary current strength at theintake entrance, which is an effective parameter in transporting sediment to the intake, showed thatit is a function of flow diversion ratio and for intake from trapezoidal channel it is less than fromrectangular channel.