a formula to calculate rate of flow of fluid in a conduit or through an opening —note 1. for steady flow discharge, Q = AV, where Q is rate of flow (ft³/sec), A is cross-sectional area (ft²), and V is mean velocity (ft/sec) —note 2. it is used to calculate the mean velocity, V, for uniform flow in pipes or open channels —see Manning's formula This definition last updated 07/17/2008