Obstruction by buildings and tree lines

Any obstruction to wind flow, including buildings and trees will produce disturbed air, manifested as wind shear and turbulence, that can significantly affect drone operations.

Effects may become very marked in strong winds on the lee side of obstructions. The figure above shows some of the effects, which are:

  • flow is disturbed to approximately three to four times the height of the obstruction [h] and 50 h downwind
  • a cushion of air with weak eddies extends 2 h to 5 h upwind;
  • the wind is accelerated above and leeward of the barrier, the greatest increases in speed being at approximately 2 h to leeward and 2.5 to 4.5 h above the ground;
  • strong eddies occupy the area up to 10 h to 15 h downwind to 2 h above the ground.

If the airflow passes through gaps in the barrier, such as with an open stand of trees, then the disturbance effects are greatly reduced. The eddy area in the lee of the barrier will be much smaller and usually does not extend above the height of the barrier.

error: Content is protected !!