Boundary layer

Boundary Layer is a concept in the field of fluid dynamics that describes the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. In the Earth's atmosphere, the boundary layer is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface.

Definition

The boundary layer is defined as the part of the flow where viscous effects play a significant role. It is typically very thin compared to the overall size of the body, but its behavior significantly affects the overall flow field and is of primary importance in many practical applications, such as aerodynamics and heat transfer.

Types of Boundary Layers

There are two types of boundary layers: laminar and turbulent.

Laminar Boundary Layer flow is characterized by smooth, constant fluid motion, while Turbulent Boundary Layer flow is characterized by chaotic, irregular fluid motion. The type of boundary layer that develops depends on the value of the Reynolds number, a dimensionless number used in fluid mechanics to indicate the type of flow.

Boundary Layer Transition

Boundary Layer Transition is the process by which a laminar boundary layer becomes turbulent. This transition is primarily dependent on the Reynolds number and the surface roughness.

Boundary Layer Separation

Boundary Layer Separation occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer relative to the object falls almost to zero. The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices.

See Also

• Fluid dynamics
• Viscosity
• Reynolds number
• Aerodynamics
• Heat transfer