Abstract
Abstract: The accurate production of a rainfall environment similar to natural rainfall by a rainfall simulator (RS) is a crucial and challenging task in rainfall instrument testing or calibration. Although the spatial uniformity of rainfall accumulation is a key parameter of an RS, the spatial uniformity comparison between simulated rainfall and natural rainfall, and the spatial uniformity improvements for an RS are scant in the literature. In this study, a fine-scale natural rainfall experiment was studied using the same testing methods of an RS and the rainfall uniformity was evaluated using the Christiansen Uniformity Coefficient (CU). Simultaneously, factors influencing the spatial uniformity of natural rainfall, including the average rainfall accumulation (RA), the deviation of RA, and the area of the test zone, were analyzed. The results successfully reproduced some of the behaviors observed in natural rainfall experiments, showing that CU is dependent on these parameters. Based on these studies, we developed a rainfall simulator with a rotary platform (RSRP) and found that although spatial uniformity of the RSRP was greatly improved using an appropriate rotary speed, it was not consistent with the spatial uniformity of natural rainfall. Furthermore, we tested four tipping-bucket rain gauges using this imperfect RSRP, and found that the RSRP might acquire the instrumental errors associated with RA for a tested rainfall instrument.
Highlights
Theartificial spatial uniformity evaluated with measuring cups were to investigate discrepancy between rainfall andwas natural rainfall
The TBRGs tested in the discrepancy between rainfall and natural rainfall.instrument
In order to have a clear understanding of the improvements to the rainfall accumulation (RA) and rainfall intensity (RI), we summarize the statistical results of RA and RI for the TBRGs
Summary
A rainfall simulator (RS) that can produce a controllable rainfall environment similar to natural rainfall is important for studying soil erosion, soil hydrological processes, and rainfall instrument testing or calibration, and can save time compared to testing during natural rainfall events [1,2]. There are two types of RSs; the first is the nozzle type, which produces rain of very high intensity and a wide range of rainfall drops that tend to give lower overall uniformity, and the other is the needle type, which produces higher uniformity but is used when one needs to simulate rain to fall from a height of 5 m or more [6,7]. Colli et al [8] designed and conducted preliminary tests of an advanced needle-type laboratory RS capable of generating discontinuous droplets with a controlled rainfall intensity and drop size distribution (DSD), but it was difficult to produce drops. In order to solve these problems, Liu et al [9] designed a nozzle-type RS prototype, and evaluated it with the Christiansen Uniformity
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