Handbook of Compressible Aerodynamics

Chapter 1

Aerodynamics: Aims, Areas of Application and Current Issues

The aim of aerodynamics is the study of the flow of air around a body, in general an air or land vehicle, this also includes an engineering structure, the rotor of a helicopter, the blades of a turbo engine or even a wind turbine, just to mention a few examples. More precisely, the intended aim is to determine the effect of the flow on the body. In fact, all fluids that flow over a material surface exert contact actions (pressure and friction) on it, which results in a force referred to as an aerodynamic force or aerodynamic resultant, obtained by integration over the whole body. This force is applied on a point called the pressure center, which generally does not coincide with the center of gravity of the body; hence an aerodynamic moment tends to make the body rotate around its center of gravity. The first goal of aerodynamics is to determine the components of force and moment. These two components play a particularly important role. The component perpendicular to the velocity of progress is the lift, which, for an aircraft at cruise conditions, is a force directed upwards, compensating the weight of the aircraft. It defines the lifting capacity of the plane, thus the payload (number of passengers and mass of freight). In a car, we instead look for a lift directed towards the ground, which pushes the vehicle to the road. The component of the aerodynamic resultant along to the velocity is drag, which opposes ...