# Aerodynamics

Aerodynamics ( from Ancient Greek ἀήρ aer, air and δύναμις dynamis, force) is part of the fluid dynamics and describes the behavior of bodies in compressible fluids ( eg air). The aerodynamics describes the forces that make it possible, for example aircraft to fly or to move sailing ships, with the help of the wind through the water. Many other areas of technology, such as civil engineering or the vehicle must come to grips with the aerodynamics.

## Specialties

Aerodynamics is a subfield of fluid mechanics (including fluid dynamics) and contains several special interest areas that are specialized in different areas:

- Wing theory: a wing movements in dense gas
- Aerospace Aerodynamics: This area deals with the aerodynamics of flight and re-entry of spacecraft
- Supersonic aerodynamics missiles move faster than sound (Mach 1 to Mach 3 )
- Hypersonic aerodynamics, missile moving at very high speed in dense gases ( Mach 3 )
- Boundary layer theory: it tight-fitting layer is viewed at close range to the body around

## Theoretical models

The most comprehensive model, the Navier -Stokes equations. It is a system of nonlinear partial differential equations of 2nd order, which describe completely a Newtonian fluid. In particular, turbulence and the hydrodynamic boundary layer are included.

A simpler model are the Euler 's equations which do not reflect a result of the friction neglected the boundary layer and do not contain any turbulence, which, for example, a stall can not be simulated by the model. This coarser mesh is substantially suitable to solve the appropriate equations. For those parts of the flow where the boundary layer does not play a significant role, the Euler equations, however, are very suitable.

The potential equations are finally useful especially if gross predictions are to be made. For them, the entropy is assumed to be constant, which means that no strong shock waves can occur because of this, the entropy is even discontinuous.

## Application

Nowadays, the aerodynamic design of aircraft and vehicles will take place mainly on the computer. Of great importance is the numerical flow simulation (CFD ), in which good approximations to real flow processes can be achieved by computerized with appropriate computational effort. For many applications, measurements are due to the complexity of the phenomena occurring in wind tunnels needed to verify the design.