What makes things aerodynamic

At the same time, a force that retards the forward motion of the aircraft is developed by diverting air in this way and is known as drag due to lift. Another kind of drag is caused by the slowing of air very near to the aircraft's surface; this can be reduced by making the surface area of the craft as small as possible. At low speeds below Mach.

The Columbia Electronic Encyclopedia, 6th ed. All rights reserved. It is harder to reshape those parts to keep airflow attached to reduce pressure drag. As the layers of air move over a rough surface, the air particles in the layer closest to the surface collide with the surface.

This makes the air particles slow right down and right at the surface, they completely stop! These particles then collide with air in layers a bit further out and make them slow down as well. As you move further away from the surface, the speed of the air particles is not affected.

The region of air where the speed of the particles has been changed is called the boundary layer. For a cyclist, the thickness of the boundary layer grows from a few millimetres to a few centimetres. The best way to reduce skin friction drag is to keep surfaces as smooth as possible. Wearing tight skinsuits makes a large difference to the speed a cyclist can reach. Frontal area is the area you see if you look at a cyclist from the front.

Reducing this area means that there are fewer collisions with the wind. Ways to reduce it include using the handlebar drops or aerobars. When the airplane is in level flight at a constant speed, the force of the thrust is just enough to counteract the aerodynamic drag. Moving air can also generate forces in a different direction from the flow. The force that keeps an airplane from falling is called lift. Lift is generated by an aircraft wing.

The path over a wing's curved top is longer than the path along the flat bottom of the wing. This causes the air to move faster over the top than it does along the bottom. With all other factors being equal, faster moving air has lower pressure than slower moving air, according to Bernoulli's principle, stated by Daniel Bernoulli , one of the most important pioneers in the field of fluid dynamics. This difference is what allows the slower moving air to push up against the bottom of the wing with greater force than the faster moving air is pushing down against the top of the wing.

In level flight, this upward force is just enough to counteract the downward force caused by gravity. Aerodynamic forces are also used to control an aircraft in flight. When the Wright brothers made their first flight in , they needed a way to control their aircraft to climb, descend, bank and turn. They developed what is known as three-axis control for pitch, roll and yaw. Pitch nose pointing up or down is controlled by an elevator the "flaps" on the back or trailing edge of the horizontal stabilizer in the tail section.

Roll tilting left or right is controlled by ailerons also flaps on the trailing edges of the wings near the tips. Yaw nose pointing left or right is controlled by the rudder on the trailing edge of the vertical stabilizer in the tail section.

These controls employ Newton's Third Law of Motion because they generate force by deflecting the airflow in the opposite direction of the desired movement. This force is also what allows aerobatic planes to fly upside down. A pilot may also use flaps on the inboard section of the trailing edge of the wing during takeoff and landing. When in the downward position, flaps increase both lift and drag to allow the plane to fly slower without stalling.

Some larger aircraft can also extend slats on the front or leading edges of the wings to increase lift at low speeds. When the smooth airflow over a plane's wing is disrupted and this reduces the amount of lift, a stall can occur.