Assessing the drop size distribution of simulated rainfall in a wind tunnel

The installation of a rainfall simulator inside the wind tunnel of I.C.E. (International Center for Eremology, Ghent, Belgium) enables to study the combined effect of wind and rain on the erosion processes. Simulated rainfall characteristics assessed were: the spatial distribution of the intensity in the working area of wind tunnel and the drop size distribution under different operating pressures and wind speed. The rainfall intensities varied between 37.9 mm h(-1) to 143.0 mm h(-1) depending on the number of operating nozzles, the applied pressure and the wind speed. Areas for different rain intensities with a uniformity coefficient higher than 80% were determined in the working area of the wind tunnel. Under simulated rainfall the raindrop diameter varied between 0.2 and 3 mm and this was affected by the operating pressure and by the wind speed. A narrower raindrop distribution and a smaller sorting coefficient, (D-75 - D-25)/D-50, was obtained under wind-driven rain (oblique rain) compared to vertical rainfall (without wind). (C) 1998 Elsevier Science B.V. All rights reserved.