Rectangular concrete blocks properly anchored into the cistern floor and projecting up to one-fourth the full supply depth are simple, effective and commonly used devices for dissipating surplus kinetic energy in hydraulic structures. The spacing between the blocks in a row is kept
about twice the height of the blocks. Depending upon the need, two or more staggered rows of these friction blocks may be provided (Fig. 10.7).
Flow
Fig. 10.7 Staggered friction blocks
The ‘arrows’ are specially shaped friction blocks (Fig. 10.8). The plan form of these arrows is approximately an equilateral triangle with rounded corners. The back face of arrows is vertical. The top of arrows is sloped from the front rounded corner to the back edge to give an upward deflection to stream filaments.
