Jawaharlal Nehru Technological University Hyderabad B.Tech II AERODYNAMICS I Previous Question Paper (September/October - 2023 - R13)

The Buckingham Pi theorem states that if a physical process involves n physical variables that are expressible in terms of m fundamental dimensions (such as mass, length, and time), then the relationship between these variables can be described by n - m independent dimensionless parameters, commonly referred to as Pi terms (π terms).

The center of pressure is the point on an airfoil chord line where the total aerodynamic force (the resultant of lift and pressure distribution) acts. At this specific location, the net moment produced by the pressure distribution is zero.

Mathematically, if the lift force is L and the moment about the leading edge is M_LE, the location of the center of pressure (x_cp) measured from the leading edge is given by:

For a symmetric airfoil, the center of pressure remains fixed at the quarter-chord point (25% of the chord) regardless of the angle of attack. For cambered airfoils, the center of pressure shifts as the angle of attack changes, moving forward as the angle of attack increases. In a diagram, this is represented by a vector originating from the center of pressure point, pointing perpendicular to the relative wind to represent lift and parallel to represent drag, with the chord line serving as the reference axis.