Calibrazione di un simulatore di pioggia per lo studio dei fenomeni di dilavamento atmosferico = Calibration of a rainfall simulator for the study of atmospheric deposition

During experimentation, it is very difficult to use natural rainfall because its timing and intensity are not reproduced reliably. Rainfall simulators are research instruments designed to study water in a similar way to storm events. They are useful for obtaining data on erosion, infiltration, surface runoff and sediment transport. The main problem it presents in replicating the characteristics of a specific natural storm event, to have representative results it is essential to have a representative natural rainfall. This thesis work, aims to calibrate the rainfall simulator in the laboratory of hydraulics of the Turin Politecnico in order to generate intensities similar to those that occur in Turin. Since there is a variation in the behavior of the simulator increasing temperature, the thesis work proposes a new calibration curve for those increments. The scope of the simulation is to study the abatement of the atmospheric particulate thanks to the processes of wet deposition. The simulator set-up consists on a drip surface at 10,70 m with a 3,50mx4,00m surface. A tank located on the top of it powered the distribution system and guarantee a constant head. The intensities that it can produces are in the range from 2mm/h to 150 mm/h. The calibration of the simulator was carried on with volumetric methods, these tests allow us to determinate the intensity variating the head. The rainfall distribution of Turin was obtained using a disdrometer located at Politecnico. These results were compared with the rainfall distribution of the simulator using a disdrometer inside it. The behavior of the simulator in front of the variation of the temperature was valuated studying the variation of the intensity of a single needle in a smaller set up cooling and heating the water used in this experimentation. Using different types of aerosols, specifically ISO Fine, Pollen, BioCarb and Fly Ash, an attempt was made to study the abatement generated by simulating rainfall drops. In this way, some results regarding the dispersing methods measures with an electrical low-pressure impactor (ELPI) and dry deposition were obtained.