Flat Plate Drag
Definitions
A boundary layer is a layer of stationary fluid surrounding a submerged moving object. The presence of a surface decreases the overall velocity, the momentum and the overall mass flow rate in the boundary layer.
Velocity boundary layer
Region of flow above the plate bounded by 𝛿 where the effect of viscous shearing forces caused by fluid viscosity are felt. The boundary layer thickness 𝛿 is typically defined as the distance y from the surface at which u = 0.99V
Boundary layer region
The viscous effects and the velocity changes are significant.
Irrotational flow region
The frictional effects are negligible and the velocity remains essentially constant.
Drag Coefficients for Laminar and Turbulent Flow
Whether the flow is laminar or turbulent flow will affect the behaviour of the flow over the plate.
Laminar zero pressure gradient flow over a plate:
If the Reynolds number is greater than 5x105 the flow is considered as turbulent and the following equations apply:
Turbulent boundary layer on a flat plate:
Turbulent boundary layer on rough flat plate:
