Airfoil Design – Boundary Layer

The most important part of an airplane is the airfoil, airflow around the airfoil generates lift.Airflow around an airfoil is like the fluid in Bernoulli’s principle. Other factors apart from the speed of air past the airfoil involved are the size of the airplane ,the shape of the aircraft and the density of the air. The pattern of airflow past an airplane depends mainly on its shape and its attitude relative to free stream airflow.

The behavior of airflow in and around the surface of the airfoil is most important. The layer we are referring to is the boundary layer. There is friction between the surface of the airfoil and the airflow , it changes the relative speed of the airflow. The air particles that are actually in contact with the surface have a relative velocity of zero. This layer is only several millimeters thick.

Smooth airflow is known as laminar airflow, at some point the air close to the airfoil changes from laminar to turbulent airflow this point where it changes is called transition point. You could ask why does the air turn turbulent? This is because on the upper surface of the airfoil there is lift being generated. There is a lower pressure (with respect to ambient pressure) developed on the upper surface of the airfoil which is curved, there comes a point when the air cannot follow the curved surface and becomes turbulent.

There is also another point on the airfoil known as separation point, this occurs during stalls and takes place when airflow on the surface of the airfoil leaves the airfoil. This point is always after the transition point.

Do remember transition point, separation point , laminar airflow and the boundary layer are all found on the surface of the airfoil. As you carry on learning you will have to remember these basics.

There are going to be points that you might not understand right now but for this level the information we have provided is more than sufficient. We are giving you the basics in the simplest form possible, so keep referring to My Aviation Tutor and you are bound to find any information related to aviation.