Abstract
It is difficult to define the hydrologic and hydraulic characteristics of rain for research purposes, especially when trying to replicate natural rainfall using artificial rain on a small laboratory scale model. The aim of this paper was to use a drip-type rainfall simulator to design, build, calibrate, and run a simulated rainfall. Rainfall intensities of 40, 60 and 80 mm/h were used to represent heavy rainfall events of 1-hour duration. Flour pellet methods were used to obtain the drop size distribution of the simulated rainfall. The results show that the average drop size for all investigated rainfall intensities ranges from 3.0–3.4 mm. The median value of the drop size distribution or known as D50 of simulated rainfall for 40, 60 and 80 mm/h are 3.4, 3.6, and 3.7 mm, respectively. Due to the comparatively low drop height (1.5 m), the terminal velocities monitored were between 63–75 % (8.45–8.65 m/s), which is lower than the value for natural rainfall with more than 90 % for terminal velocities. This condition also reduces rainfall kinetic energy of 25.88–28.51 J/m2mm compared to natural rainfall. This phenomenon is relatively common in portable rainfall simulators, representing the best exchange between all relevant rainfall parameters obtained with the given simulator set-up. Since the rainfall can be controlled, the erratic and unpredictable changeability of natural rainfall is eliminated. Emanating from the findings, drip-types rainfall simulator produces rainfall characteristics almost similar to natural rainfall-like characteristic is the main target.
Highlights
Rainfall simulators are usually used to produce the artificial rainfall under controlled conditions, which is found to be useful in surface hydrology and studies of soil erosion whether in laboratory or in field
For 60 mm/hr, raindrops per minute are 192, with 13.3 grams per minute of a discharge. These results shows that the discharge rate and the 155 number of drops per minute increased as the rainfall intensity increased
A rainfall simulator was designed, calibrated, and tested to produce heavy rainfall intensities (40, 60 and 80 mm/hr), meeting 260 all of the major requirements formulated at the beginning of the conceptual planning
Summary
Rainfall simulators are usually used to produce the artificial rainfall under controlled conditions, which is found to be useful in surface hydrology and studies of soil erosion whether in laboratory or in field. Infiltration is useful 25 to model the behaviour of soil, in particular with the soil reaction under the influence of rainfall intensities. The impact of the rainfall on soil surface causing dislodging soil particles and splashing. Most of the splashed soil, resulting in surface pores clogging which in turn reduces water infiltration, increases water runoff, and increases soil erosion. Rainfall simulators can provide more consistent control over an experiment, as well as faster data collection and repeatable testing.
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