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The drag equation may be derived to within a multiplicative constant by the method of dimensional analysis. If a moving fluid meets an object, it exerts a force on the object. Suppose that the fluid is a liquid, and the variables involved – under some conditions – are the: speed u, fluid density ρ, kinematic viscosity ν of the fluid,
The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface.
is the frictional force – known as Stokes' drag – acting on the interface between the fluid and the particle (newtons, kg m s −2); μ (some authors use the symbol η ) is the dynamic viscosity ( Pascal -seconds, kg m −1 s −1 );
Skin friction drag is a type of aerodynamic or hydrodynamic drag, which is resistant force exerted on an object moving in a fluid.Skin friction drag is caused by the viscosity of fluids and is developed from laminar drag to turbulent drag as a fluid moves on the surface of an object.
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation. [8] [4]
The force required to drag an "attached" layer of air with the body is called skin friction drag. Skin friction drag imparts some momentum to a mass of air as it passes through it and that air applies a retarding force on the body. As with other components of parasitic drag, skin friction follows the drag equation and rises with the square of ...
The force F required to overcome drag is calculated with the drag equation: = Therefore: = Where the drag coefficient and reference area have been collapsed into the drag area term. This allows direct estimation of the drag force at a given speed for any vehicle for which only the drag area is known and therefore easier comparison.