Aerodynamics

The branch of dynamics concerning the study of motion of air, particularly when it interacts with a moving object is known as aerodynamics. Aerodynamics comes under the topics, fluid dynamics and gas dynamics. Aerodynamics is mostly used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases. The motion of free air (often called a flow field) around an object enables to calculate the force and moments acting on the object. The properties which are used to calculate for a flow field include velocity, pressure, density and temperature as a function of position and time. By introducing the topic control volume around the flow field, equations for the conservation of mass, momentum, and energy can be defined and used to solve for the properties.

Need for Aerodynamics:

Aerodynamics in Car Design:

The manufacturers give first preference for the design of the car, with aerodynamics as an afterthought. With the help of aerodynamics much can be gained by tweaking the aerodynamics of these vehicles. The Aerodynamics is measured by a factor called the "coefficient of drag" or Cd. The Cd tells us how efficiently the vehicle slips through the wind. Lower Cd means better Mileage!

Aerodynamics in Aircraft:

As aircraft are design to travel faster, aerodynamicists realized that the density of air began to change as it came into contact with an object, leading to a division of fluid flow into the incompressible and compressible regimes. In the study of compressible aerodynamics, density and pressure both change, which is the basis for calculating the speed of sound. The first one to develop a mathematical model for calculating the speed of sound was Newton, but it was not correct until Pierre-Simon Laplace accounted for the molecular behavior of gases and introduced the heat capacity ratio. The ratio of the speed of sound to the flow speed was named the Mach number after Ernst Mach, who was one of the first to investigate the properties of supersonic flow which included Schlieren photography techniques to visualize the changes in density.