发音101—Day 29

Laminar flow

The laminar boundary layer is a verysmoothflow,createsless skin frictiondragthan the turbulent flow but isless stable. Boundary layer flow over a wing surfacebegins as a smooth laminar flow.As the flow continues back from the leading edge, the laminar boundary layer increases in thickness.

Turbulent flow &transition region

At some distance back from the leading edge, the smooth laminar flowbreaks downand transitions to a turbulent flow. It is advisable to have the transition from laminar to turbulent flowas far aft on the wing as possibleor have a large amount of the wing surface within the laminar portion of the boundary layer.

Airflow separtion

Airflow separation occurs when the airflow breaks away from an airfoil. Thenatural progressionis from laminar boundary layer to turbulent boundary layer and then to airflow separation. Airflow separation produceshigh drag and ultimately destroys lift. Theboundary layer separation pointmoves forward on the wing as the angle of attack (AOA) is increased.