The Coanda effect is the phenomenon where a rapidly advancing air stream, instead of following a straight path, adheres to a nearby level and follows the slopes of the level.
This physical phenomenon is called the Coanda effect, named after the Romanian inventor Henri Coandă, who first detected it. Henri Coanda dealt with the issue when the prototype of the airplane he designed in 1910 crashed due to this event.
The most common application of this effect is in aviation. The winglets, which bend down to stop and land on aircraft wings, and up when taking off, are designed based on this effect.