The physical principle of "candle that can't be blown out" is "wall-attached effect". When the funnel is used to blow out candles, air flows out along the wall, forming an air vortex in the funnel. If the candle is put far away, it will not stop blowing; If you put it close, the flame of the candle will run in instead, as if it had been sucked.
where the convection is fast, the air pressure is weak, and the blown air will be pushed back by the larger air pressure around the candle before it reaches the candle. So even if you blow hard, it won't work.
Extended information
Discovery of the wall attachment effect:
The early description of this phenomenon was provided by Thomas Young in his speech to the Royal Society in 18: the lateral pressure of pushing the flame of a candle blowing from the air pipe into the air flow in the future may be completely similar to the pressure of relieving the inflection point of the air flow near the obstacle.
mark a long and thin air flow pit on the water surface. Contact the convex body with one side of the fluid, and the position of the pit will immediately show that the current deflects towards the body; If the body can move freely in every direction, it will be forced to develop in the current direction.
one hundred years later, Henry Kolandi discovered his Coand in his experiment. -The application of the 191 plane, which designed an unusual engine. Electric turbines push hot air backwards, Coand? Notice that the airflow is attracted to nearby surfaces.
in 1934, Coand? A patent for "Method and device for transferring fluid to another fluid" was obtained in France. This effect is described as "deviation of the average jet of a fluid permeating another fluid near the convex wall".