Rainfall Energy Characteristics of a Modified Kamphorst Simulator

This manuscript presents the characterization of a modified Kamphorst rainfall simulator performed in the laboratory of the Department of Agricultural, Food, and Forest Sciences of the University of Palermo. In particular, the factory capillary tubes of the Kamphorst simulator (10 mm long, with an inner diameter of 0.6 mm) have been substituted by using stainless-steel capillary tubes having a length of 28 mm and an inner diameter equal to 0.6 and 0.8 mm, respectively. The original and the two modified configurations have been characterized in terms of rainfall kinetic power and momentum using different pressure head and water temperature conditions and by applying weighing and photographic techniques. Specifically, the mean mass of single raindrops was assessed by weighing a fixed number of drops, while their fall velocity was measured for several falling heights by analyzing the displacement of a single drop between two consecutive frames obtained by a high-resolution and high frame-rate video. This analysis aimed to understand how, for a fixed test condition, the geometric features of the capillaries could influence the simulated rainfall characteristics, such as the intensity and the energetic characteristics. Finally, the reliability of the recently proposed relation- ships for estimating the simulated rainfall intensity, momentum, and kinetic power are tested for the original and modified Kamphorst simulators.