 Discharge coefficient

A discharge coefficient multiplies an ideal inviscid opening-flow rate to represent contraction and dissipative losses. Its value depends on the opening geometry and flow regime.

The discharge coefficient (often denoted as \( C_d \)) is a dimensionless number used in fluid dynamics to characterize the flow through an orifice, nozzle, or other flow constrictions. It represents the efficiency of the flow as it passes through a restriction relative to the theoretical flow predicted by Bernoulli's equation.