A dimensionless number used in momentum transfer in general and free settling velocities and resistance to flow calculations in particular. Proportional to (Gravitational force) / (Inertial force).

CD = (g (rho-rhof) L) / (rho V2)

g: gravitational acceleration, L: characteristic dimension of object, rho: density of object, rhof: density of surrounding fluid, V: velocity


Back to Dimensionless Numbers