The different flow speeds of gas and liquid generate pressure waves, breaking up the liquid into extremely fine drop particles.
The different relative speeds allow atomizing e.g. of viscous liquids at low pressure. Pneumatic atomizers operate both according to internal and external mixing principles, whereby gas and liquid mix inside or outside the nozzle. Depending on the nozzle design, liquid is either supplied by siphon action or by gravity. According to the configuration of the nozzle tip, different spray patterns may be obtained.