Wind tunnel analysis of spray drift of slow-evaporating herbicide carriers

Abstract

Research was conducted to compare the atomization and drift characteristics of several herbicide carriers under controlled environmental conditions in a horizontal wind tunnel. The wind tunnel had a height of 4.25 ft and was operated with a center air velocity of 150 fpm. Also, the air stream turbulence was reduced to a low level. Experiments were conducted under two different air conditions, 90°F - 20 percent relative humidity and 70°F - 90 percent relative humidity, having a high and low evaporative potential, respectively. Two types of experiments were conducted in the wind tunnel. One type involved the introduction of sprays from flat fan nozzles into the wind tunnel. Measurements of the amount of spray material drifting downwind from the nozzle were made. In the other type of experiment, discrete sizes of droplets were injected into the wind tunnel. The horizontal distance that a particular size of drop traveled before depositing on the tunnel floor was measured. The initial size of droplets ranged from 100 to 500 microns in diameter. ...