Rotor induced air movements and their effects on droplet dispersal

Abstract

The dispersal of droplets sprayed from an aircraft, be it fixed or rotary winged, is affected by influences which can be placed in four categories:1. Particle characteristics e.g. terminal velocity.2. Aircraft wake.3. Meteorology.4. Nozzle or atomiser position.Although all four categories combine to produce a particular application the relative importance of each influence varies with particular circumstances. Large particles for instance, are little influenced by air movement and so aircraft wake and meteorology are unimportant. Small droplets, on the other hand, have low terminal velocities and are more easily affected by air movements. Situations where wake predominates over meteorology are usually those where flying heights and wind speeds are low. For example, in Ultra Low Volume spraying, Lawson and Uk (1979) found wake effects at low flying heights.