FORCES AND MOMENTS ACTINGON A FLIGHT VEHICLE:
EQUATION OF MOTION OF RIGID VEHICLE:
DIFFERENT TYPES OF DRAG:
Skin Friction Drag
That part of the drag which is caused by shear stress at all points on the body concerned where it is touched by the fluid in which it is immersed, it acts tangentially to the surface. It is due entirely to the viscosity of the fluid in which the body is immersed.
Is pressure drag due to flow separation.
Profile Drag is the sum of Form drag and Skin Friction drag. It is the drag to which the Drag Coefficient Cd refers, for two dimensional airfoil sections and that wings and rotor blades are three dimensional.
Induced drag is dependent upon lift production and is not usually associated with viscous effects. In fixed wing terms the induced drag is caused by part of the lift vector being inclined rearward due to the downwash created by the formation of vortices at the trailing edge which causes the relative wind to be inclined downwards, reducing the angle of attack of the aerofoil. Remember lift is defined as that part of the force which acts at 90 degrees to the relative airflow.