One uses the Bernoulli principle. The Bernoulli principle says that in the same fluid, the flow rate is large and the pressure is small; the flow rate is small and the pressure is strong. The fluid will automatically flow from high pressure to low pressure. When passing through the trigeminal tube (the specific picture can not be drawn, I understand it), the low-speed flowing water flows to the high-speed flowing air. The water is torn by a high-speed air into a small drop (assuming that the water flowing out of the faucet is slow at the beginning, it is a water column; but then the speed gradually increases and becomes a drop). When these small water droplets are sprayed out, they become fog.
The second type is to press water into the thin tube to cause high-speed water flow, and the high-speed water flow breaks into obstacles and then breaks into small water droplets. The situation is like blocking the faucet and blocking it with your fingers. Household sprayers use this structure and are low in cost.
The third is to let the water carry a charge (water is a dielectric), using the same kind of charge to repel each other and divide the water into droplets. The droplets of this method are small. The same principle is also used to paint cars.
The fourth type is ultrasonic atomization. Vibration can cause "spray" on the surface of the water. The vibration frequency of the ultrasonic wave is very high, so its "wave" has a very small wavelength, so its "spray" - small water droplets are also small, and these small water droplets become fog. In the hospital, the throat machine for treating respiratory diseases is atomized by ultrasound.

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