Assessment of Velocity Profile Variation of Hydraulic Jump in Relation to Changes in the length of Roughness

In this study, the variation of velocity profile at different sections of hydraulic jump were evaluated in
relation to changes in the length of roughness on a rough bed performing the tests in a flume with
length of 12m, width and the height of 0.40m. Nine profile variation tests were carried out for 3
Froude numbers and 3 lengths of roughness. In each test, four sections of hydraulic jump were
selected in which the velocity was measured at 1 cm intervals. The impact of changes of roughness
length on velocity profile was surveyed at short, medium and long reaches of effective length. The
results indicated that although the dimensionless velocity profiles on the rough bed are similar, their
shapes are different from that of on a smooth bed. The boundary layer was another subject studied in
this research. The results showed that the boundary layer thickness increased with an increase in the
length of roughness and finally dimensionless boundary layer thickness reaches the values of 0.26 for
short and 0.37 for medium and long roughness lengths.