Required Head Loss over Long-Throated Flumes

Long-throated flumes, all with the same trapezoidal throat, were laboratory tested. The flume throat was first fitted with two entrance transitions with plane bottoms converged respectively 1:2, and 1:3, as measured relative to the flume center line. The 1:2 transition has no significant influence on the flume calibration. The throat was then tested with six downstream transitions of which the expansion ratio ranged from 1:0—1:10. Two flume series were tested with these transitions. The modular limits and related required energy head losses were analyzed. An equation is presented to estimate the modular limit for any long-throated flume placed in an arbitrary canal; a procedure to calculate this modular limit is also presented.