Analyse expérimentale des écoulements transitoires diphasiques dans le système de drainage urbain

The operational problems and rapid filling of sewer network systems can generate a pressurization wavefront, by which the air can be entrapped and get highly pressurized. Also, during the emptying process and returning to the normal condition, a depressurization wavefront is generated, the air can enter the sewer network systems, and a sub-atmospheric pressure can occur in the systems. Note that, during both pressurization and depressurization processes, the hydraulic infrastructure can be seriously damaged. The consequences can include burst, collapse, contamination of the water table, or flooding. Therefore, the transient flows in sewer network systems are studied in two different experiments. In the first experiment, the emptying process of a pressurized flow is simulated under two different initial conditions: 1) when the water is stagnant in the pipe (zero flow) and 2) when the water flows at a constant rate (steady flow). In the second experiment, a partially pressurized flow, a pressurized flow at upstream, and a free-surface flow at downstream, is developed in a pipe, which is supplied by a reservoir connected at the upstream end. The air existing at the top of the free-surface flow is entrapped by suddenly obstructing the downstream end. Note that the results of this experiment are also used to study the effect of unsteadiness behavior of friction losses in numerically simulating the flow variables, including pressure and flow rate.