Volumeflow

Volumeflow, or volumetric flow rate, is a measure of the volume of fluid that passes through a cross-sectional area per unit time. It is commonly denoted Q and is used in engineering, physics, and fluid dynamics to quantify how much fluid moves through a system.

Mathematically, Q equals the cross-sectional area A times the average fluid velocity v perpendicular to the area, Q = A v. For nonuniform flows, the volumetric flow rate is the integral of the velocity field over the cross-sectional area, Q = ∫_A v · dA. The SI unit is cubic meters per second (m^3/s); it is also common to use liters per second (L/s) or gallons per minute in engineering practice.

Volumetric flow is related to mass flow rate ṁ by ṁ = ρ Q, where ρ is the fluid density. In compressible or temperature/pressure varying flows, Q can depend on state conditions, and standard volumetric flow rates may be reported at reference temperature and pressure (STP). For liquids with nearly constant density, Q is approximately constant for a given operating condition; for gases, Q can vary significantly with pressure and temperature.

Measurement of volumetric flow can be done with various flow meters, including differential-pressure devices (Venturi, orifice plates) that infer Q from a pressure drop, turbine meters that relate rotative speed to flow, and ultrasonic or electromagnetic meters that infer velocity profiles. Some instruments measure mass flow directly, from which Q can be derived if density is known.

Applications include water supply and treatment, chemical processing, HVAC and aeronautics, and many industrial process systems where the rate of fluid delivery is critical.