What is aerodynamics and why is it important?

Definition Aerodynamics: 

Aerodynamics is the study of how air flows around objects like aircraft, trains, cars, and buildings. The term "air" refers to any gaseous medium, including helium or other gases, depending on the situation. Aerodynamic forces and moments generated by the flow of air past an object enable it to fly. 

These flows can occur due to an aircraft's motion through the air or the motion of flowing air past a stationary model in a wind tunnel. Aerodynamics is a crucial component of aerospace engineering.

There are three approaches to modern aerodynamic studies: experimental, theoretical (analytical or semi-analytical), and computational fluid dynamics (CFD). 

Each approach has its advantages and disadvantages. Typically, the most effective approach is to combine experimental and theoretical/CFD investigations in a rational manner to solve specific problems.

Experimental studies are performed in wind tunnels, where aerodynamic measurements are taken on scaled-down models of prototypes. 

Measurements of pressure on the model surface, forces and moments acting on the model, wake surveys and flow visualization are conducted to gain valuable insight into the flow problem. 

However, this approach has some drawbacks, including high capital and running costs of wind tunnels, the need for skilled personnel to manufacture models accurately and acquire data, and the difficulty of maintaining the Mach and Reynolds numbers simultaneously, which are essential for maintaining dynamic similarity between the flow past a scaled-down model in a wind tunnel and that around an actual prototype in flight.

Theoretical and CFD studies have led to a valuable understanding of a wide range of flow problems. However, these approaches also have limitations. 

The main limitation arises from the fact that the Navier-Stokes equations, which describe real viscous compressible flow around an object, cannot be solved theoretically in general. 

While the equations are capable of providing a detailed description of all flow regimes of interest to aerodynamicists, highly accurate numerical solutions of the governing equations are required, subject to suitable initial and boundary conditions, making the computations extremely expensive and impractical for routine use. 

Therefore, simplified forms of the Navier-Stokes equations are often used, with the simplest form being the Laplace equation under the assumption of inviscid, incompressible, and irrotational flow. 

A variety of correction schemes have been developed to incorporate effects due to viscosity and compressibility in the solution of the Laplace equation. These correction schemes provide alternative solutions to the Navier-Stokes equation. 

Applications: 

In the past, most aerodynamic research was carried out in wind tunnels. However, nowadays computers are used to model airflow. This means that we can study aerodynamics without the need for expensive and dangerous experiments.

Aerodynamics is an important part of many different fields. For example, in racing, aerodynamic principles are used to make cars go faster. In golf, aerodynamic principles are used to design clubs that help the ball travel further.

Aerodynamics is a fascinating subject that is constantly evolving. It is important because it helps us to understand how things fly and to make them more efficient.