The numerical simulation using a boundary element method is presented for a gas bubble bursting at a free surface in a potential flow with a viscous fluid assumption. Systematic comparisons are given with experimental data on the first "jet drop" size in relation with the parent bubble size, and on the critical bubble radius above which no jet drop forms. The computations were made for different liquids. It is pointed out that an exact description of the jet formation and break up requires the complete Navier-Stokes equations only in the final phase of the evolution.

Our paper aims at assessing the way in which EPANET estimates the efficiency of variable speed pumps operating at speeds different from the nominal speed. An experimental setup, existing at the Technical University of Civil Engineering Bucharest, was modelled in EPANET 2. The facility allows the measurement of the characteristic curves of two identical pumps driven by electric motors with the rotational speed ratio of ½. The pumps curves were fed into EPANET and results for different rotational speeds were compared to measured values. Results show that EPANET does not alter pump's efficiency curve when operating at different rotational speeds.

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The present study proposes a chlorination schedule calibrated for the Drinking Water Distribution Network (DWDN) of Buzau  a medium sized city, in South-Eastern Romania. The numerical model of Buzau's DWDN was set up in EPANET, considering the main pipes of the network that interconnect 4 pumping stations and 45 booster stations (viewed here as end-users). The calibration of the numerical model was based on real-time recordings available for January and July 2014. The chlorination scheduling was simulated at each reservoir supplying a pumping station, by a variable injection pattern added to the EPANET DWDN model. The injected amount of chlorine was determined by values of the chlorine concentration obtained at 4 key monitoring points, spread over the network. The simulations were performed over an extended time period of 72 hours. The system behaviour has been analysed for two cases: with all pumping stations in operation, and with the biggest pumping station shutdown. For each case, the proposed schedule corresponds to the injection in the network of less chlorine than the corresponding recorded values for January and July 2014, and yet obtaining at the 4 key points a chlorine concentration variation similar to the recorded one, while the chlorine concentration at the end users was within the admissible range, across the whole DWDN.

No abstract