Aerodynamic Forces, Moments & Wind Engineering – Key Vocabulary 2

Vocabulary flashcards covering core aerodynamic forces, moments, principles, coefficients, drag types, and related wind-engineering terms from the lecture notes.

Aerodynamic Forces

Forces generated by air flowing over a body; primarily lift and drag.

Lift

Upward aerodynamic force perpendicular to the freestream flow that counters weight and enables flight.

Drag

Resistive aerodynamic force acting parallel and opposite to the direction of motion.

Resultant Force

Vector sum of lift, drag, and weight acting on an airborne object.

Pitching Moment

Torque about the lateral (y-) axis that raises or lowers an aircraft’s nose.

Bernoulli’s Principle

Fluid-dynamics law: as velocity increases, static pressure decreases.

Newton’s Second Law of Motion

Acceleration is proportional to net force and inversely proportional to mass (F = m a).

Newton’s Third Law of Motion

For every action there is an equal and opposite reaction.

Airfoil

Cross-sectional shape of a wing or blade designed to generate lift when air flows around it.

Angle of Attack (AoA)

Angle between an airfoil’s chord line and the incoming airflow; key factor in lift and stall.

Lift Coefficient (CL)

Dimensionless number expressing lift capability of a surface; L = ½ ρV²S CL.

Drag Coefficient (CD)

Dimensionless measure of an object’s resistance to flow; D = ½ ρV²S CD.

Pitching Moment Coefficient (CM)

Dimensionless value representing pitching moment magnitude; M = ½ ρV²Sc CM.

Reynolds Number (Re)

ρVL/μ; predicts laminar vs. turbulent flow regimes.

Mach Number (M)

Ratio of object speed to local speed of sound (V/a).

Skin Friction Drag

Drag due to shear stress between air molecules and a body’s surface.

Form Drag

Pressure drag arising from an object’s shape and flow separation regions.

Induced Drag

Drag generated as a by-product of lift; caused by wingtip vortices and spanwise pressure differences.

Wave Drag

Additional drag produced by shock waves as an aircraft approaches transonic/supersonic speeds.

Center of Pressure (CoP)

Point on an airfoil where the resultant aerodynamic force acts.

Mean Aerodynamic Chord (MAC or c)

Average chord length of a wing; reference length for moments and coefficients.

Freestream Velocity (V∞)

Undisturbed airspeed far ahead of a body; used in aerodynamic calculations.

Air Density (ρ)

Mass per unit volume of air; influences lift, drag, and moment magnitudes.

Wing Surface Area (S or A)

Planform area of a wing; directly proportional to generated aerodynamic forces.

Skin Friction Coefficient (Cf)

Non-dimensional quantity indicating shear drag on a surface.

Gust Load

Transient force and moment spikes caused by sudden wind velocity changes.

Thrust

Propulsive force pushing an aircraft forward, counteracting drag.

Weight

Gravitational force acting downward on an aircraft’s mass.

Stall

Condition where excessive AoA causes lift to drop sharply due to flow separation.

Wave Drag Divergence Mach

Flight Mach number where wave drag rises steeply due to shock-wave formation.

Aerodynamic Stability

Ability of an aircraft to return to equilibrium after a disturbance without pilot input.

Wind Engineering

Field studying wind effects on structures, vehicles, and environments for safety and efficiency.

Induced Angle of Attack

Effective change in AoA due to downwash from wingtip vortices.

Newton’s Second Law of Motion

“The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.”