What is free stream flow in an aircraft?

Free stream flow in an aircraft refers to the undisturbed flow of air relative to the aircraft. It is the air that the aircraft encounters as it moves through the atmosphere. The free stream flow is characterized by its velocity, density, and temperature.

The velocity of the free stream flow is determined by the aircraft's speed and the direction of the aircraft's flight path. The density of the free stream flow is determined by the altitude at which the aircraft is flying. The temperature of the free stream flow is determined by the ambient temperature and the aircraft's speed.

The free stream flow is important in aircraft design and analysis because it is the starting point for understanding how the aircraft interacts with the air. The free stream flow conditions are used to calculate the aerodynamic forces and moments acting on the aircraft. These forces and moments are used to determine the aircraft's performance, stability, and control characteristics.

The free stream flow can be affected by a number of factors, including the presence of other aircraft, buildings, or terrain. These factors can cause the free stream flow to become turbulent or unsteady, which can affect the aircraft's performance.

In order to accurately predict the aerodynamic forces and moments acting on an aircraft, it is necessary to have a detailed understanding of the free stream flow conditions. This can be done using computational fluid dynamics (CFD) simulations or wind tunnel testing.