When any hydraulic structure like a dam, weir, barrage or bridge is built across a waterway, the regimen conditions of the waterway gets altered. Due to the raising of the water level on the upstream section of the structure, the velocity of the discharge through and downstream of the structure becomes more than what it was before the structure was built. This results in the erosion of the bed of the waterway, to prevent which care must be taken to dissipate the energy of the flow before the flow reaches the bed of the normal waterway.
Stilling basins and their appurtenances are being designed from a long time to destroy this detrimental flow energy. Enormous amount of work has been done to improve and formulate the general principles of basin design, though of course, ad-hoc procedures are to be sought to meet certain design requirements which may be peculiar to a particular basin.
The use of friction blocks to destroy the energy of flowing water under hydraulic structures has been investigated by quite a good number of of investigators. Investigators like Thomas, Blaissdell, Bradley, Patrica and many others have contributed a lot to the subject and in the Hydraulic Research Liboratory atthe Indian Institute of Science, the investigations have been carried out to arriveat the best geometry for the body to dissipate the flow energy. Of the several shapes tested, the rectangular body shape was found to be the most efficient in dissipating the flow energy at high velocities. This paper deals with the test data based on the experiments conducted to know the energy characteristics of certain types of friction blocks which may be used as hydraulic energy dissipators in stilling basins.
