Aerodynamics Cheat Sheet

The core ideas of Aerodynamics distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Lift

The aerodynamic force acting perpendicular to the oncoming airflow that supports an object against gravity. It is generated primarily by a pressure difference between the upper and lower surfaces of a body such as a wing.

Drag

The aerodynamic force acting opposite to the direction of motion, resisting the movement of an object through the air. It has two main components: pressure drag (form drag) and skin-friction drag (viscous drag).

Bernoulli's Principle

A statement derived from conservation of energy for a flowing fluid: in a steady, incompressible, inviscid flow, an increase in fluid speed occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

Boundary Layer

The thin layer of fluid adjacent to a solid surface where the flow velocity transitions from zero at the wall (no-slip condition) to the free-stream velocity. It can be laminar or turbulent and significantly affects drag and heat transfer.

Reynolds Number

A dimensionless quantity that characterizes the ratio of inertial forces to viscous forces in a flow. It determines whether a flow will be laminar or turbulent and is defined as Re = (density x velocity x characteristic length) / dynamic viscosity.

Mach Number

The ratio of the speed of an object or flow to the local speed of sound. It classifies flow regimes: subsonic (M < 1), transonic (M near 1), supersonic (1 < M < 5), and hypersonic (M > 5).

Angle of Attack

The angle between the chord line of an airfoil and the direction of the oncoming relative airflow. Increasing the angle of attack generally increases lift up to a critical point, beyond which stall occurs.

Stall

A condition in which the airflow separates from the upper surface of a wing due to an excessive angle of attack, causing a sudden loss of lift and a sharp increase in drag. It is an aerodynamic event, not an engine failure.

Vortex and Induced Drag

Drag that results from the generation of lift on a finite wing. High-pressure air beneath the wing spills around the wingtips to the low-pressure region above, creating trailing wingtip vortices that deflect the oncoming airflow downward (downwash).

Computational Fluid Dynamics (CFD)

A branch of fluid mechanics that uses numerical analysis and data structures to solve and analyze problems involving fluid flows. Computers simulate the interaction of fluids with surfaces by solving discretized forms of the governing equations.

Key Terms at a Glance

Aerodynamics:The branch of fluid dynamics dealing with the study of air and its interaction with solid bodies in motion.

Airfoil:A cross-sectional shape designed to produce an aerodynamic force (lift) when moving through air.

Angle of Attack:The angle between the chord line of an airfoil and the direction of the oncoming undisturbed airflow.

Aspect Ratio:The ratio of wingspan to mean chord, indicating how long and narrow or short and wide a wing is.

Bernoulli's Principle:A statement that in steady, incompressible, inviscid flow, increases in velocity correspond to decreases in static pressure.

Boundary Layer:The thin region of fluid adjacent to a surface where the flow velocity varies from zero at the wall to the free-stream value.

Camber:The curvature or asymmetry between the upper and lower surfaces of an airfoil.

Chord Line:The straight line connecting the leading edge to the trailing edge of an airfoil.

Circulation:The line integral of velocity around a closed curve enclosing a body; directly related to lift via the Kutta-Joukowski theorem.

Computational Fluid Dynamics:The use of numerical methods and algorithms to simulate fluid flow by solving discretized governing equations on computational grids.

Drag:The aerodynamic force acting opposite to the direction of motion, resisting an object's movement through air.

Downwash:The downward component of airflow deflected by a lifting wing, which reduces the effective angle of attack and creates induced drag.

Flow Separation:The detachment of the boundary layer from a surface due to an adverse pressure gradient, creating a recirculating wake region.

Induced Drag:Drag that is a byproduct of lift generation on a finite wing, caused by wingtip vortices and downwash.

Laminar Flow:Smooth, orderly fluid motion in which adjacent layers slide past one another without mixing.

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