Effect of Roughness Height on the Length of B-jump at an Abrupt Drop

ABSTRACT: Normally downstream of any chute and sluice gate there is a hydraulic jump type stilling basin to dissipate the excessive energy of the high velocity flowing flow through the structure. The dimensions of this basin depend on the length of jump. In some cases there is a sudden drop on the bed of jump which alter the jump properties. The aim of the present paper is to study the effect of roughened bed on flow characteristics of hydraulic jump at abrupt drop. Total of 75 tests conducted in a wide flume of 80 cm in width and 15 meter long. Experimental tests were performed for wide range of Froude numbers ranging from 3.03 to 11.68. The experimental results show that roughening bed of stilling basin can reduce the jump length as much as about 40%. The results herein reported may be helpful in the design of a stilling basin with a negative step and rough beds.