Abstract
ABSTRACT Rainfall Simulators (RS) have been used as tools for researches involving the estimation of runoff and infiltration on permeable pavements as well as in evaluating storm build-up and wash-off processes on pavements and roofs. Data obtained with the use of RS allows building a database with parameters which are useful in the implementation of BMPs taking local environment conditions into consideration. The purpose of this study was to develop and calibrate a handy and low-cost RS for hydrological researches. The developed RS can reproduce rainfall with intensities from 40 mm h-1 to 182 mm h-1. The RS is able to simulate rainfall events with drops of median diameter (D50) of 2.12 mm and kinetic energy of 22.53 J mm-1m-2, which represent 90.12% of the kinetic energy produced by a natural rainfall. Spatial distribution of simulated rainfall, which is expressed by the Christiansen's Uniformity Coefficient, was considered satisfactory with a value of up to 87.80%. The developed RS can be used as an alternative for the acquisition of hydrological data in a reduced period of time, under standardized experimental conditions and independently of natural rainfall events. The RS is also capable to simulate rainfall events with varying intensity.
Highlights
Rainfall simulators (RS) are equipment used to create rain events with specific pre-established characteristics
Renard (1985) presents some limitations of rainfall simulator (RS) use, being: (a) the area plots used in the experiments are usually small, ranging from a fraction of square meter to hundreds of square meters, depending on the simulator, and small areas cannot be representative of the researched area; (b) most RSs do not produce raindrop size distribution that represent drop size of natural events; (c) several RSs do not simulate events with rainfall intensity with the temporal variation of natural rainfall, and (d) some RSs do not produce raindrops that reach the terminal velocity of natural raindrops
The objectives of this research were: (a) to design and construct a RS for studies of urban hydrology that seeks to overcome some limitations of other RSs already developed; (b) to evaluate the rainfall produced in terms of drop size, fall time, terminal velocity, kinetic energy and spatial distribution of simulated rainfall, and (c) determine the effect of simulation time and rainfall intensity in the spatial distribution of simulated rainfall
Summary
Rainfall simulators (RS) are equipment used to create rain events with specific pre-established characteristics. Its use allows greater experimental control over variable properties that govern natural rainfall events, such as intensity and duration of the event, drop size, kinetic energy and rainfall spatial distribution. RSs have many advantages, such as the ability to reproduce rainfall events with similar characteristics, possibility of raindrop diameter variation, kinetic energy, rainfall duration time and intensity. Renard (1985) presents some limitations of RS use, being: (a) the area plots used in the experiments are usually small, ranging from a fraction of square meter to hundreds of square meters, depending on the simulator, and small areas cannot be representative of the researched area; (b) most RSs do not produce raindrop size distribution that represent drop size of natural events; (c) several RSs do not simulate events with rainfall intensity with the temporal variation of natural rainfall, and (d) some RSs do not produce raindrops that reach the terminal velocity of natural raindrops. There are RSs that works at high pressure, which can reach the kinetic energy of natural rainfall
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