TRANSITION SUBMERGENCE AND HYSTERESIS EFFECTS IN THREE-FOOT CUTTHROAT FLUMES

摘要

New and detailed hydraulic laboratory measurements for a 3-foot Cutthroat flume with fourrndifferent throat widths were collected and analyzed. It was found that there is no definitelyrnobservable transition submergence at which the regime changes from free to submerged, andrnvice versa. It was also found that no hysteresis effect on the calibration is observable in the 3-ftrnCutthroat flume when moving from low to high submergence, or from high to low submergence.rnThe laboratory data demonstrate that previously published transition submergence, S_t, values dornnot accurately describe the hydraulic behavior of this Cutthroat flume because S_t is not constantrnfor given flume dimensions – it varies with flow rate. Various criteria were applied to thernlaboratory data to define the curvilinear relationship of S_t with flow rate, thereby providing arnmore accurate application of the traditional free- and submerged-flow equations, in those casesrnwhere their continued use is desired. The observed S_t at the maximum discharge in each of the four throat widths was strongly correlated with the previously published St values.