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Interference drag is greater when two surfaces meet at perpendicular angles, and can be minimised by the use of fairings. [6] [7] [5] Wave drag, also known as supersonic wave drag or compressibility drag, is a component of form drag caused by shock waves generated when an aircraft is moving at transonic and supersonic speeds. [1]: 25, 492, 573
Parasitic drag, or profile drag, is the sum of viscous pressure drag (form drag) and drag due to surface roughness (skin friction drag). Additionally, the presence of multiple bodies in relative proximity may incur so called interference drag, which is sometimes described as a component of parasitic drag. In aeronautics the parasitic drag and ...
is the drag coefficient – a dimensionless coefficient related to the object's geometry and taking into account both skin friction and form drag. If the fluid is a liquid, c d {\displaystyle c_{\rm {d}}} depends on the Reynolds number ; if the fluid is a gas, c d {\displaystyle c_{\rm {d}}} depends on both the Reynolds number and the Mach number .
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.
Wave drag is independent of viscous effects, [2] and tends to present itself as a sudden and dramatic increase in drag as the vehicle increases speed to the critical Mach number. It is the sudden and dramatic rise of wave drag that leads to the concept of a sound barrier .
Parasitic drag – also known as profile drag, [170]: 254 [171]: 256 is a type of aerodynamic drag that acts on any object when the object is moving through a fluid. Parasitic drag is a combination of form drag and skin friction drag. [172] [170]: 641–642 It affects all objects regardless of whether they are capable of generating lift.
In the simplest case of a flat plate parallel to the incoming flow, boundary-layer theory results in (friction) drag, whereas all inviscid flow theories will predict zero drag. Importantly for aeronautics, Prandtl's theory can be applied directly to streamlined bodies like airfoils where, in addition to surface-friction drag, there is also form ...
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 );