Theory of differential pressure flow measurement
Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full

A fluid is considered incompressible if its density does not vary significantly under the effect of the negative pressure used to measure its flow velocity. Since this article is primarily concerned with the engineering and practical aspects of flow measurement using depressurizers, we will confine ourselves to theoretical developments, which can be consulted in the basic literature. A brief summary can be given, however, based on the energy conservation equation established in 1738 by Daniel Bernoulli for an incompressible fluid: