Aerodynamics is the branch of dynamics that deals with the motion of air and other gaseous fluids and with the forces acting on bodies in motion relative to such fluids. The Latin word for aero means air, and the Latin word for dynamics means power.
             Steady aerodynamics this term is used to describe situations where there is no rapid change in properties over time. For example, an aircraft cruising straight and level in the upper atmosphere, well above where any gust can reach it. When such situations are being analyzed, a lot of effort can be saved by neglecting terms in the equations, which describe rates of change of the flow properties or forces at any point on the aircraft.
             Time-accurate strong-interaction models for the coupling of a boundary-layer method with a method for three-dimensional, unsteady, compressible potential flow about elastically deforming wings are developed. The investigation of the flow behind on oscillating airfoil has shown that two waves of convected vortices can be distinguished: One wave convected at, roughly, the outside uniform velocity; and an inner wave in the core of the wake originating at the trailing edge which is convected at a much lower speed. At a certain distance behind the airfoil there is a partially destructive interference, which depends on the reduced frequency. For the flow above a circle-cylinder it is shown that giving small symmetric displacements from its equilibrium position to a vortex pair positioned near the circle-cylinder, periodic oscillations set in. Expressions for closed orbits and their periods are obtained. For the large amplitude case the vortex trajectories are calculated numerically. For a circle-cylinder with strakes the vortex motions may be periodic, quasi-periodic or the vortices may be swept away, depending on the initial conditions. From the equations of motion of flexible slender bodies with constant crosssections immersed in a uniform axial flow, expressio...