Search results
Results from the WOW.Com Content Network
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.
It is inversely proportional to the negative acceleration: a high number indicates a low negative acceleration—the drag on the body is small in proportion to its mass. BC can be expressed with the units kilogram-force per square meter (kgf/m 2 ) or pounds per square inch (lb/in 2 ) (where 1 lb/in 2 corresponds to 703.069 581 kgf/m 2 ).
Note the minus sign in the equation, the drag force points in the opposite direction to the relative velocity: drag opposes the motion. Stokes' law makes the following assumptions for the behavior of a particle in a fluid: Laminar flow; No inertial effects (zero Reynolds number) Spherical particles; Homogeneous (uniform in composition) material
These deceleration constant factors can be verified by backing out Pejsa's formulas (the drag curve segments fits the form V (2 - N) / C and the retardation coefficient curve segments fits the form V 2 / (V (2 - N) / C) = C × V N where C is a fitting coefficient). The empirical test data Pejsa used to determine the exact shape of his chosen ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
The most typical case of air resistance, in case of Reynolds numbers above about 1000, is Newton drag with a drag force proportional to the speed squared, =. In air, which has a kinematic viscosity around 0.15 cm 2 /s, this means that the product of object speed and diameter must be more than about 0.015 m 2 /s.
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.