ABSTRACT
This chapter discusses the relationship between the volume flow and the differential head created when a restriction such as an orifice plate or a venturi section is placed in the flow stream. The magnetic flowmeter uses the principle of voltage induction, and the vortex meter uses vortex shedding as a means of measuring volumetric flow, and these instruments are gradually replacing the orifice plate and venturi meters. The bluff body presents an obstruction to the fluid flow, causing the flow stream to divide, and in so doing causes a change in the velocity profile of the stream, the lowest velocities being near the bluff body. Turbine flowmeters are constructed around a set of unpowered and freely rotatable hydro- or aerofoils held like an aircraft or marine propeller on the central longitudinal axis of the pipeline. The chapter concludes by stating that ultrasonics is used in flow measurement, and for this a source of the ultrasound and a receiver is needed.
