I hope some experts can offer guidance and explain the selection process for average velocity tube flowmeters in detail. Thank you!

The basic principle of these flow meters is the same; they are all flow meters that utilize the principle of dynamic pressure. The energy that fluid in motion retains as a result of its flow is known as dynamic pressure energy. The dynamic pressure energy of a fluid is related to its flow velocity; when the motion state of the fluid changes, its dynamic pressure energy is converted into dynamic force that acts on the object responsible for changing that fluid’s motion state. By measuring the force exerted on this object or directly measuring the dynamic pressure, it is possible to determine the flow velocity, and thus obtain the flow rate. ●　The ancestor of this type of flowmeter is the pitot tube (shown below). It measures dynamic pressure energy using an open tube that faces the flow stream (a dynamic pressure tube); in simple terms, when the flow hits the opening of the tube, it is obstructed, and the dynamic pressure is converted into pressure ； The pressure in the pipeline is measured using another tube with an opening perpendicular to the flow direction (a static pressure tube); the pressure difference between the two tubes is related to the flow velocity of the medium. Its output differential pressure (△P) and fluid average velocity (V) are given by the classical Bernoulli equation: 　　　　　V＝ K×(2／ρ×△P)＾(1/2) 　　where ； △P— the difference between total pressure and static pressure, kPa ； 　　　　　ρ — density of the fluid under operating conditions, Kg/m3 ； 　　　　　k — correction coefficient. 　　If expressed in terms of flow rate, the basic formula for calculating it is: 　　　　　Qv＝K×π/4×D2(2ΔP/ρ)＾(1/2) 　　Where: Qv represents the flow rate of the fluid passing through the measuring tube, in m3/h ； 　　　　　D — Inner diameter of the measuring tube in mm. ●　The pitot tube has a fatal flaw: it can only measure the flow velocity at one point in the pipe. The flow velocity of the medium at the center of the pipe and near the pipe wall is different. To solve this problem, the approach adopted is to measure the dynamic pressure at multiple points and take their average. Thus, a measuring tube shaped like a flute was developed; in China it is called a flute-shaped tube based on its shape, or a uniform-flow tube based on its function, while abroad it is known as an Anubas. ●　Thus, the basic problems of measurement have been resolved. But there are still some “minor issues” that affect accuracy. Those “ba” here and those “ba” there are actually the results of using different methods to solve these “small problems”. ●　The minor issues mentioned above can be roughly categorized into several types: the pressure at the opening of the dynamic pressure tube is uneven, with a pressure level close to the actual dynamic pressure in the center and lower pressures at the periphery; moreover, this pressure is affected by the flow pattern and flow velocity ； 　　To avoid the influence of the pipe walls, reduce disturbances to the flow field within the pipe, and for installation reasons, the static pressure tube is usually placed behind the dynamic pressure tube. Behind the obstacle in the fluid, a region of negative pressure as well as disturbances are formed (refer to the formation of vortex streets) ； 　　The effect of the measuring tube itself on the flow field within the pipe. ●　The general solutions include: changing the cross-section of the measuring tube to reduce the impact of the flow beam on the sampling port ； 　　Change the cross-section of the measuring tube to eliminate the influence of the flow beam behind it ； 　　Utilize the negative pressure behind the measuring tube to increase the signal amplitude and compensate for the effect of the flow beam on the dynamic pressure tube ； 　　………… ●　Toba is a variant of the pitot tube ； 　　Bitoba, Delta Ba, and Wei Li Ba are variations of Anuba ； 　　Ainiuba, uniform-speed tube, and flue tube are different names for the same thing. ●　As for the advantages and disadvantages of this “Ba” and that “Ba”, as well as their areas of application and the various claims made by manufacturers, users are basically unable to verify them. In my opinion, aside from the fact that it can indeed improve measurement accuracy, there is no significant difference. Moreover, this improvement in accuracy is largely due to an increase in manufacturing precision as well. So when making a selection, it mainly depends on the technical specifications provided; as long as they are suitable, that’s fine. .

Could this problem be approached from another angle, by treating the existing items that need to be measured as the issues to be resolved? It seems quite difficult to become familiar with all the flow meters available on the market; as technology advances, new measuring instruments will continue to emerge. This has little applicability to actual choices. If it is specifically for metrology* research, then it is a different matter. For reference.

It’s each manufacturer that comes up with its own name; essentially, they are all uniform-flow tube flowmeters