Computer simulation of factors affecting drift from a forestry airblast sprayer

Sidahmed, M.M. and Brown, R.B. 2002. Computer simulation of factors affecting drift from a forestry airblast sprayer. Canadian Biosystems Engineering/Le genie des biosystemes au Canada 44: 2.272.35. Previous studies have demonstrated the adequacy of the computational fluid dynamics code (FLUENT) for simulating spray dispersal and deposition. In this study FLUENT was used to determine the effects of weather and operating parameters on the behavior of droplets and consequences on drift and deposition with an airblast forestry sprayer (Algonquin). The investigated parameters included initial droplet sizes (Do=20-300 :m), temperature (T= 293 and 301 K), relative humidity (RH= 40, 69, and 80%), airblast outlet velocity (U = 30 and 48 m/s), and droplet projection angle (2 = 0, ±22.5, and ±45). Temperature and RH had a pronounced influence on final droplet size, but had little effect on the horizontal distance traveled by droplets with Do>70 :m. Conversely, U and 2 had a significant effect on horizontal distance traveled by droplets with Do>70 :m, but had little influence on final droplet size. Maximum possible swath ranged from 15 to 21 m for the variation of parameters investigated. Low RH caused excessive evaporation and should be avoided even at low temperature. High RH and low T conditions retarded evaporation while increasing both deposition within a spray swath and particle and airborne drift. High airjet speed and abovehorizontal projection of droplets reduced deposition while increasing total particle and airborne drift. In all cases, drift would be drastically reduced by selecting nozzles that produce fewer small droplets (<110 :m) and orienting the nozzles downward (around –22.5).