Development of a rainfall simulation system using hypodermic needles

摘要

A rainfall simulation system of 10 m x 1.4 m size has been developed by using hypodermic needles. The development was based upon the findings of a calibration test performed to obtain an appropriate combination of design variables like needle size, needle to needle spacing, line to line spacing and operating water pressures so as to obtain generated rainfall parameters in the range which commensurates with natural rainfall. It was observed that the developed rainfall simulation system generates continuous rainfall with its intensity in the range of 63.0 mm h~(-1) to 170.8 mrnh~(-1), uniformity coefficient87.52% to 92.1%, drop size 3.05 mm to 4.67 mm and the terminal velocity of raindrops 7.674 m s~(-1) to 9,496 m s~(-1) for 20 no. size of hypodermicneedle at aneedle to needle and line to line spacing of 20 cm x 20 cm with operating water pressures in the range of 0.1 kg cm~(-2) to 0.6 kg cm~(-2). The developed rainfall simulation system is simple and economical in construction, easy in operation and is capable of generating rainfall with its parameters fairly comparable with the natural rainfall.