An apparatus and method for measuring the flow rates of each component of two-phase flow consisting of a gas and a liquid or three-phase flow consisting of water, oil and gas, including a first volumetric flow meter stage, and second and third momentum flow meter stages coupled in a series flow path with the volumetric flow meter stage and in which a velocity ratio between the gas and the liquid in the series flow path is maintained to be one. A processor calculates flow rates of the components of flow by solving volumetric flow and momentum or energy equations defining flow through the first through third stages utilizing a volumetric flow output from the first stage and momentum flux outputs from said second and third stages, and an indicator displays flow of liquid and gas or oil, water and gas components of the flow. To measure three-phase flow, a water-cut meter is provided to determine the amount of water flow, which is then used by the processor to determine the flow of the rest of the liquid. The second and third momentum flow meter stages can be implemented by two separate momentum flow meters or by a single momentum flow meter, such as a venturi flow meter having a venturi nozzle including pressure taps for obtaining at least two differential pressure measurements. In the event that the density of the liquid component is known, a single momentum flow meter stage is sufficient. IMAGE
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