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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.
Drag is a force that acts parallel to and in the same direction as the airflow. The drag coefficient of an automobile measures the way the automobile passes through the surrounding air. When automobile companies design a new vehicle they take into consideration the automobile drag coefficient in addition to the other performance characteristics ...
For an object with well-defined fixed separation points, like a circular disk with its plane normal to the flow direction, the drag coefficient is constant for Re > 3,500. [17] The further the drag coefficient C d is, in general, a function of the orientation of the flow with respect to the object (apart from symmetrical objects like a sphere).
Sometimes different reference areas are given for the same object in which case a drag coefficient corresponding to each of these different areas must be given. For sharp-cornered bluff bodies , like square cylinders and plates held transverse to the flow direction, this equation is applicable with the drag coefficient as a constant value when ...
The drag curve or drag polar is the relationship between the drag on an aircraft and other variables, such as lift, the coefficient of lift, angle-of-attack or speed. It may be described by an equation or displayed as a graph (sometimes called a "polar plot"). [1] Drag may be expressed as actual drag or the coefficient of drag.
Universal sedimentation equation — drag coefficient, a function of Reynolds number and shape factor, 2D diagram Universal sedimentation equation — drag coefficient, a function of Reynolds number and shape factor, 3D diagram. This is why mathematically all Newtonian, incompressible flows with the same Reynolds number are comparable.
In mechanics and aerodynamics, the drag area of an object represents the effective size of the object as it is "seen" by the fluid flow around it. The drag area is usually expressed as a product , where is a representative area of the object, and is the drag coefficient, which represents what shape it has and how streamlined it is.
English: Drag coefficient C d for a sphere as a function of Reynolds number Re, as obtained from laboratory experiments. The dark line is for a sphere with a smooth surface, while the lighter-colored line is for the case of a rough surface. The numbers along the line indicate several flow regimes and associated changes in the drag coefficient: