Choked flow is a phenomenon that limits the mass flow rate of a compressible fluid flowing through nozzles, orifices and sudden expansions. Generally speaking it is the mass flux after which a further reduction in downstream pressure will not result in an increase in mass flow rate.
The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems. Orifices and nozzles are typically used to deliberately reduce pressure, restrict flow or to measure flow rate. This article gives typical values of the discharge coefficient for common orifice and nozzle designs.
This article provides calculation methods for correlating design, flow rate and pressure loss as a fluid passes through a nozzle or orifice. Nozzles and orifices are often used to deliberately reduce pressure, restrict flow or to measure flow rate.
Restriction orifices and control valves are commonly used for pressure reduction and measurement of flow rates, however for a liquid system, excessive pressure drop across these items of equipment may result in cavitation. This article describes methods of predicting cavitation across restriction orifices and valves and proposes designs which may be used to avoid cavitation.