STUDY OF SHAPE OF INTERMEDIATE SILL ON THE DESIGN OF STILLING BASIN MODEL

The stilling basins are used to dissipate the energy of flowing water and protect the downstream structures like spillways, canals, etc. from the scouring. The aim of the present experimental investigation is to design the new stilling basin models for non circular pipe outlet using intermediate sill of different shapes having height equal to the diameter of pipe outlet. The experimental study was carried out for three Froude numbers namely 3.85, 2.85 and 1.85 for pipe outlet. Scour index (SI) has been used to evaluate the performance of stilling basin models with different shapes of intermediate sill, tested using same sand base material and test run time. The scour pattern was measured for each test run and flow pattern was also observed. After twelve tests runs, it was found that scour process were reduced for a shaped of intermediate sill having height equal to the diameter of pipe outlet at a particular location of intermediate sill combined with end sill of particular size and shape along with impact wall. Performance of this model having square shaped intermediate sill was found to be much better than USBR VI impact basin model for similar flow conditions