Effect of aerofoil geometry on droplet size distribution in a pneumatic spray nozzle by VOF simulations

Spray nozzles for pesticide spraying in unmanned drones have in recent years increased in interest. In this application, achieving a consistent droplet size from the nozzle is essential for the success. In this study, the effect of geometrical changes of a pneumatic nozzle, operating at ReD = Ub,aD/nu(a) = 20,000, on droplet size distribution is investigated by applying CFD using the Volume of Fluid method.In this study, we will analyse how geometrical changes of a pneumatic nozzle affect droplet size distribution, by applying CFD using the Volume of Fluid method for ReD = Ub,aD/nu(a) = 20, 000. The aerofoil geometry within the nozzle is altered by the addition of a step-like geometry to analyse how water separation occurs on the plate and thus impacts the droplet distribution. It is concluded that when adding steps, the water film is more likely to separate. This is pronounced at lower step counts and smaller step angles. This results in droplets of amore consistent size being formed. While keeping the step angle of 90 deg, a decreasing step count shows an increasingly uniform droplet size distribution. The same phenomenon is found for the step angle, where, at a constant step count of 4, a decrease in the step angle increases droplet size consistency.