Recirculation

Imagine the airflow which was directed to the ground to create the air cushion in a  ground effect is now rebounding off the ground going back up into the top of the rotor system. When it passes back through the rotor again it gets accelerated. This process may continue with the air velocity increasing each time as it passes through the rotor. Eventually, the velocity is so great that the air going into the rotor from above causes a loss of lift and the helicopter will sink toward the ground unless the pilot increases power. This means that if recirculation is occurring, the helicopter will need mone power to hold a constant height. Recirculation will not always happen but will be aggravated by the type of ground or nearby obstacles causing the air which is trying to escape out to the sides of the helicopter to be directed back up toward the rotor system. The result is 'recirculation' of downwash air.



The following Scratch Project explains the whole process of recirculation in a very interactive way.

Recirculation of Helicopter


Simple simulation to explain recirculation in helicopters.

The helicopter can be controlled using the arrow keys.

The helicopter will show air movements based upon the position.

If the helicopter goes near the obstacle on the right, increased airflow towards the right side of the rotor will push it away.




Mobile Version of Recirculation of Helicopter on Scratch









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