Consider flow exiting a nozzle into atmosphere, its static pressure will decrease through the nozzle as the molecules vectors align with the direction of the exit. However, as soon as it exits the static pressure should become atmospheric as contact with the atmospheres molecules will add perpendicular vectors and thus give it the same static pressure. This has been shown to be true through simple experiments measuring the static pressure inside flow emerging from a fan or hair dryer (see the first link).

Then how come it can be demonstrated that a flame will bend towards the emerging airflow from a hairdryer? (see second link). In all texts i've found it has been explained by bernoullis principle. Except there should not be a lower static pressure, is it actually because of entrainment?




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