An annubar is similar to a pitot tube used to measure the flow of gas or liquid in a pipe. The pitot tube measures the difference between the static pressure and the flowing pressure of the media in the pipe. The volumetric flow is calculated from that difference using Bernoulli's principle and taking into account the pipe inside diameter. [1] The biggest difference between an annubar and a pitot tube is that an annubar takes multiple samples across a section of a pipe or duct. In this way, the annubar averages the differential pressures encountered accounting for variations in flow across the section. A pitot tube will give a similar reading if the tip is located at a point in the pipe cross section where the flowing velocity is close to the average velocity. (Wikipedia)

Flow analysis around an annubar in a circular pipe has been carried out using computational fluid dynamics (CFD) code, ‘FLUENT’ to establish the effect of body shape on the annubar factor. It is found out that the annubar factor for elliptical shape with high slenderness ratio has the highest annubar factor and minimum permanent pressure loss. Rounding of the edges of a standard diamond shaped annubar improves its performance. The permanent pressure loss is comparatively lower than that for the orifice meter and the annubar factor is constant above a critical Reynolds number. The annubar factor reduces with increase in blockage factor. (Analysis of the effect of body shape on )

This paper analyses the defects in the construction of conventional Annubar flowmeter and explores a new Annubar flow sensor with piezoelectric crystal. A new detection scheme is also decided on the base of theoretical analyses and a great number of experiments. An integrated Annubar flowmeter whose core is PIC microprocessor is developed in order to lower costs (The application of piezoelectric element)