Author(s): Menendez Ciro
Linked Author(s): Ciro Galo Menéndez Alcazar
Keywords: Low slope-stepped chute; Nappe flow; Skimming flow; Energy dissipation
Abstract: The present work is related with the experimental results obtained for low slope-stepped storm sewers (θ=5.71°) of the Historical Site of Quito city-Ecuador, for evaluating the energy dissipation for a discharge range between 1 and 10 m3/s, tested on a physical model of scale 1:8. For testing, two stepped chutes of 0.15 m width and h/l= 0.1, were taken, where h is the step high and l is the step length; chute 1 consisted of six 0.0625-m high, 0.625-m long horizontal steps while chute 2 had twelve 0.03125-m high, 0.3125-m long horizontal steps. Nappe, transition and skimming flow regimens were observed during the tests for the scaled discharge range from 5.5 l/s to 55/s. Velocity flow and water depth at cross sections upstream of the step edges and on the end downstream of the chutes-where hydrostatic pressure distribution was obtained for each discharge, were measured and mean pressures on the horizontal and vertical step face were measured as well. The results of data processing showed that for the chute with 6steps and ten discharges tested, the percentage of energy dissipated decreased from 78% to 52% for yc/h between 0.85 and 2.12 for nappe flow and from 46% a 37% for skimming flow for yc/h between 2.4 y 3.87. For the chute with 12 steps the energy dissipation decreased from 77% to 65% for yc/h between 1.7 and 3.5 for nappe flow, and from 57% to 41% for skimming flow for yc/h between 4.23 y 7.73; where yc is the critical depth for each discharge; therefore, for more number of steps on the chute more energy is dissipated on low slope-stepped chutes like on similar channel with higher slope.
Year: 2009