Improved calibration of Cutthroat flumes
An analysis of laboratory data for a 0.914-m (3-ft) length Cutthroat flume with four different throat widths is presented. Significant differences with previously published calibration parameters were found. Special attention was given to non-hydrostatic pressures at the upstream and downstream piezometer taps, and the variations are presented in a series of three-dimensional plots. Variation in relative pressure at different tap heights was observed and was concluded to represent a shift from a concave to a convex flow profile between the 0.305- and 0.203-m throat widths. This significant alteration in the flow profile correlates with a sharp change in the nf calibration parameter, describing a non-linear relationship with flume throat width. Alternative equation forms were explored in an attempt to increase the predictive accuracy of the calculated flow rates for free- and submerged-flow regimes. The alternative equations showed a decrease in the percent error, in the submerged-flow regime, by more than 50%. Transition submergence was observed to vary not only due to flume size, but also to flow rate. An empirically fitted equation was developed to calculate the transition submergence as a function of throat width and flow rate. In addition, a separate calibration for free-flow parameters was defined based on measurements from an upstream point gauge. The flow measurement accuracy of existing Cutthroat flumes can be significantly increased, especially for submerged-flow regimes.
Cut‐Throat Flume Characteristics
The characteristics of cut-throat flow measuring flumes are examined with special attention to scale effects and the transition submergence at which the flow regime changes from undrowned to drowned. Three flumes were tested over a scale range of 1:4. The results for undrowned flumes indicate a small scale effect at low flow rates only. The noted scale effect is completely eliminated by adjusting the data to correct for dissimilar boundary layer growth. The results for drowned flow indicate no scale effect for relative submergences below 0.85. Above this value an apparent scale effect is noted although it is shown to be of little practical consequence. The value of transition submergence is shown to be nonconstant and dependent on the discharge through the structure. A physical explanation for this behavior is put forward. It is concluded that hydraulic model studies of cut-throat flumes are feasible provided the submergence is kept below 0.85 and the entrance and exit conditions are modeled correctly in addition to the flume itself.
A numerical study on liquid ring motion and fragmentation for the initial process of liquid explosive dispersal
For the explosive dispersal on liquid fuel of FAE technique, the expansion of gaseous detonation products, axisymmetric radial extension and fragmentation of a liquid ring were analyzed, then corresponding models were established. By those models coupled, the numerical simulation on motion and fragmentation of the liquid ring exerted by strong action was carried out. The results computed show that the models established are feasible, and present study can offer initial conditions for the numerical simulation on the process of liquid secondary breakup and gas-liquid mixing.