MEASUREMENT OF FORCE VS TIME RELATIONS FOR WATERDROP IMPACT

Force vs. time relationships of waterdrop impact are important for understanding the process of erosion caused by soil splash. Waterdrop impact forces were measured for 3. 31-, 3. 83-, 4. 51-, and 5. 25-mm diam drops falling from a height of 14. 0 m onto piezoelectric transducers with rise times of 2 and 5 mu s. Peak forces occurred within 13 to 21 mu s of initial contact, ranged from 1. 0 to 3. 8 N, and decreased to 0. 5 N after approxiamtely 100 mu s. Average pressure under impact were calcualted from the force measurements and an approximation of waterdrop contact area as a function of time and decreased to 100 kPa after 50 mu s. The results indicated that the times and magnitudes of the force of impact were poorly predicted from currently used models and that the compressional wave generated in the water upon impact is probably an important parameter in determining the level and time distribution of forces during impact.