Fluids formulae – January 2012

BOUNDARY LAYERS

Displacement thickness: ∫ (

)

Momentum thickness: ∫

(

)

Shape factor:

Skin friction coefficient:

Drag coefficient:

Laminar boundary layer velocity profile:

(

)

Turbulent boundary layers:

, √

,

(viscous sublayer),

(overlap region)

:

Smooth flat plate boundary layers Quantity Laminar flow

(103<Re<106) Turbulent flow

Re>106

Boundary layer thickness,

Displacement thickness,

Momentum thickness,

Shape factor, H 2.59 1.28 Skin friction coefficient, Cf

Drag coefficient, CD

Flat plate, fully rough:

(

)

,

(

)

LIFT AND DRAG

Lift coefficient

Drag coefficient:

Aspect ratio:

Increase in angle of attack:

Drag coefficient for finite aerofoil:

Stall speed : √

Safe minimum landing speed (FAA):

Spin ratio: