STUDY OF FLOW CHARACTERISTICS OVER A SHARP-CRESTED TRIANGULAR WEIR USING CFD

Abstract

The focal objective of this study was to evaluate the effect of the slope of the channel on the coefficient of discharge for the Sharp crested triangular weir using CFD software (Ansys fluent) for clear flow and simulations on plane gravel bed. Weirs are regularly used to control the stream paces of waterways during times of high release. Floodgate entryways (or now and again the stature of the weir peak) can be adjusted to increment or diminishing the volume of water streaming downstream. In this work, we calculated different parameters including point velocities for the channel and weir. For the validation of results, experimental data for the same setup were being used where data was collected for the clear flow and gravel bed in a rectangular flume over a triangular weir. Modelling of the same setup was done in Ansys fluent using VOF (Volume of Fluid) multiphase analysis and results were compared. Percentage error is thus calculated which was found to be in 5-10% range. Also with the increase in slope the coefficient of discharge tends to increase upto 3% of slope, after that it minutely decreased for next 1% of positive slope. Using Discrete phase modelling with Erosion/accretion physical models, particles (sizing of 20 microns to 200 microns) were traced with their residence time and 95% of the particles were found to be passing over the triangular weir. Also with Eulerian multiphase model in a 2-Dimensional setup, sediment analysis was done using sand with the help of patch tool. And their flow behavior was tracked down until they went into suspension state.