ABSTRACT
The most commonly measured variables are mass, temperature, length, flow rate, pressure and level in tanks and hoppers. Commercially, flow measurement is one of the most significant. Laminar flow is said to occur when the fluid particles move in layers or laminae. Fluid particles close to a large plate will move in a plane parallel to the plate surface and parallel to each other. The theoretical modelling of non-steady flow is complex. Laminar flows have a lower resistance to flow and so are preferred in some situations such as long pipelines in order to give greater pumping efficiency. The correlation technique has been used in applications where the more traditional flowmeters cannot operate well. The measurement of flow using ultrasound has become an established technique in the process industries. Relative motion between a transmitter and receiver gives the well-known Doppler frequency-shift effect. The measurement of blood flow-rate is of significant importance in a number of clinical specialisms.
