# Aerodynamic 2

Flow classification[ edit ] Flow velocity is used to classify flows according to speed regime. Building on these developments as well as research carried out in their own wind tunnel, the Wright brothers flew the first powered airplane on December 17, Compressible flow accounts for varying density within the flow.

This difference most obviously manifests itself in the case of a fluid striking an object. Of these, lift and drag are aerodynamic forces, i.

Main article: History of aerodynamics Modern aerodynamics only dates back to the seventeenth century, but aerodynamic forces have been harnessed by humans for thousands of years in sailboats and windmills, [2] and images and stories of flight appear throughout recorded history, [3] such as the Ancient Greek legend of Icarus and Daedalus.

Effects of compressibility are more significant at speeds close to or above the speed of sound. Density, flow velocity, and an additional property, viscosityare used to classify flow fields.

During the time of the first flights, Frederick W. Further information: incompressible flow An incompressible flow is a flow in which density is constant in both time and space.

Conservation laws[ edit ] The assumption of a fluid continuum allows problems in aerodynamics to be solved using fluid dynamics conservation laws.

## Aerodynamic 2

Above Mach 0. Subsonic flows are often idealized as incompressible, i. William John Macquorn Rankine and Pierre Henri Hugoniot independently developed the theory for flow properties before and after a shock wave , while Jakob Ackeret led the initial work of calculating the lift and drag of supersonic airfoils. Flows for which viscosity cannot be neglected are called viscous flows. Main article: Hypersonic In aerodynamics, hypersonic speeds are speeds that are highly supersonic. In its most complete form, the momentum conservation equations are known as the Navier-Stokes equations. A fourth classification, hypersonic flow, refers to flows where the flow speed is much greater than the speed of sound. In many aerodynamics problems, the forces of interest are the fundamental forces of flight: lift , drag , thrust , and weight. In the s, the term generally came to refer to speeds of Mach 5 5 times the speed of sound and above. The validity of the continuum assumption is dependent on the density of the gas and the application in question. For example, many aerodynamics applications deal with aircraft flying in atmospheric conditions, where the mean free path length is on the order of micrometers and where the body is orders of magnitude larger.

Internal aerodynamics is the study of flow through passages in solid objects.

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