Chapter 11 Flashcards
What are the 2 types of drag experienced when an object is in an airflow
Form drag
Skin friction drag
What types of drag fall under parasite drag?
Form Drag
Skin friction drag
Interference drag
What factors effect skin friction drag?
Speed: The faster the speed of the airflow, the greater the speed
difference between adjacent layers of molecules in the boundary laver,
leading to higher shear forces and thus greater skin friction drag.
Surface Area: A larger aircraft has more skin friction drag because it
has a larger surface area, covered by a boundary layer, which slows a
greater volume of air.
Boundary Layer Conditions: A turbulent boundary layer causes more
skin friction drag than a laminar boundary layer.
What happens to induced drag as speed is increased?
When speed is increased induced drag deceases as the aircrafts angle of attack decreases to maintain straight and level flight. The pressure differences between the top and bottom of the wing decreases thus decreasing wing tip vortices.
When does induced drag increase?
Aircraft mass. Heavy aircraft requires more lift.
Manoeuvre. An aircraft requires excess lift to manoeuvre. More drag in the turn.
What is form drag effected by?
Air speed. The greater the airspeed the greater the drag.
Frontal area. Large frontal area means more drag.
Shape and streamlining. Streamlining reduces drag.
Surface. Rough surface means more drag.
What does total drag comprise of
Form drag and parasite drag.
What is the formula for induced drag?
induced drag = ½ p V2 S Cd
Coefficient of induced drag is
Inversely proportional to aspect ratio
Directly proportional to coefficient of lift squared.
What type of drag do fairings and fillets help reduce
They help reduce interference drag
