39 Fluid dynamics

Based on the image you sent, here's an overview of fluid dynamics:

Fluid dynamics and aerodynamics

Fluid dynamics is the study of how gases and liquids flow around objects. Aerodynamics, a branch of fluid dynamics, specifically deals with airflow and is relevant to designing aircraft, vehicles, and structures. Aerodynamic testing can be conducted in wind tunnels by blowing air at high velocity, and analysis can be done using computational fluid dynamics (CFD) with complex simulation software.

Drag

Aerodynamic drag (or simply drag) is the resistance an object experiences when moving through the air. It's quantified by the drag coefficient. Streamlined objects have low drag coefficients, reducing the force exerted on them by airflow. There are different types of drag:

• Form drag: Depends on the shape of the object.
• Skin friction: Drag caused by air flowing over the surface of the object.
• Pressure drag: Results from the pressure difference between the air upstream and downstream of the object.
• Interference drag: Depends on the amount of turbulence around the object.

Laminar and turbulent flow

In aerodynamics, engineers focus on the airflow in the boundary layer (the air close to the surface of an object). If an object is streamlined, the airflow in the boundary layer will be laminar, following a direct, clean path. A less streamlined object creates turbulent airflow, which is disturbed and messy. Turbulent flow produces more drag than laminar flow and generates a bigger wake (the V-shaped zone of turbulent air behind the object). Wakes contain vortices, twisting flows similar to water going down a plughole in a bath.

Aerofoils

Aerofoils are components designed to manipulate airflow in specific ways. Examples include:

• Aircraft wings: Generate lift (upward aerodynamic force).
• Propeller blades and helicopter rotor blades: Generate thrust to propel aircraft through the air.
• Wings on racing cars: Generate downforce (downward aerodynamic force).

Aerofoils have cross-sectional shapes with their leading edge (the front edge relative to the airflow) shaped differently from their trailing edge (the rear). The behavior of air around an aerofoil depends on airflow velocity and the aerofoil's angle of attack (or pitch) relative to the airflow.

Ответ: See above for a detailed summary of the fluid dynamics concepts from the image.

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