Meaning
Local separation of a laminar boundary layer followed by transition and reattachment creates a localized region of stagnant flow on an aerodynamic surface. Known as a laminar separation bubble, this phenomenon increases drag and alters the pressure distribution along the wing or blade. This change can severely degrade the aerodynamic efficiency of drones and wind turbine rotors.
Boundary Layer
Adverse pressure gradients force the thin boundary layer to detach from the surface before it becomes turbulent. Inside the laminar separation bubble, the fluid circulates slowly before transitioning to a turbulent state that can reattach downstream. This behavior is highly sensitive to the angle of attack.
Aerodynamic Penalty
The presence of these bubbles can lead to premature stall and reduced lift at low Reynolds numbers. Understanding and managing the laminar separation bubble allows wind turbine blade manufacturers to optimize the contour of the airfoil. This optimization is required for maximizing energy production in low-wind conditions.
Performance Warranty
Contracts for the supply of wind turbines include strict energy yield guarantees that depend on the aerodynamic efficiency of the blades. If a blade design produces an unexpected laminar separation bubble, the resulting power output shortfall can trigger heavy financial penalties. In such cases, the blade manufacturer must deploy aerodynamic modifications, such as vortex generators, to eliminate the problem.
This correction is done at the expense of the supplier to restore the turbine to its warranted performance level.
