SEWER PRESSURIZATION MODELLING BY A RIGID-COLUMN METHOD

Mathematical modelling of pressurization transient by a rigid-column method is studied based on previous laboratory testing. Of course, such a method is not able to simulate the experimental intense pressure oscillations; however, it is considerably simpler than other feasible methods and more easily implementable within drainage network models. Starting from this operative point of view, the paper aims at recognizing “what” and “how much” of the transient can be simulated by a rigid-column method. Actually, better results were obtained than it was expected. The model proves to be successful in simulation of the filling pipe stage as well as the stabilization stage of flow to the final steady values, during which it reproduces rather well the “mean” surge (i.e. the surge filtered out of the oscillations). This means that, in order to study floods in urban drainage networks, oscillation simulation is not necessary, whereas it is necessary in stability analysis of sewers. Comparison between the simulated and experimental pressure diagrams allows one better to recognize the different stages of the total phenomenon as well as the influence of some geometric and hydraulic parameters. Simulation of the intense oscillations and investigation of their true nature will be tackled in further papers.