Study Of Flowrate Measurement Characteristics Of A Circular Cylinder With A Slit

Vortex flowmeter is a kind of flowmeter based on the performance of flowaround a bluff body. It is widely used in gas, liquid and steam flow measurement.Flow around a bluff body is a complex phenomenon which is influenced by suchfactors as bluff body structure, fluid flow condition and so on. Bluff body is a keycomponent of vortex flowmeter and it affects flow measurement property andresistance characteristic of vortex flowmeter. Circular cylinder with a slit is a newtype of bluff boy structure which can stabilize vortex shedding and enhance theintensity of vortex. This paper takes circular cylinder with a slit in vortex flowmeterand the mainly works are listed as follows:1、Mechanism of flow past a circular cylinder with a slit was analyzed in theory.In the process of vortex periodic shedding boundary layer suction and blowingproduced by fluid on both side of the slit change periodically. The slit can be thoughtof as a feedback channel. In the process of vortex generation and shedding on a sidesuction and blowing function can speed up vortex formation on the other side andenhance vortex intensity.2、Fluid field of flow past a circular cylinder with a slit at different Reynoldsnumber was simulated. The relationship between vortex frequency and velocity andthe distribution of circumference wall static pressure was obtained. Vortex sheddingprocess was analyzed as well. The comparing results of vortex signal property amongcircular cylinder with a slit, circular cylinder and trapezoidal cylinder indicates theadvantages of circular cylinder with a slit. Finally the best signal detection positionof circular cylinder with a slit was obtained.3、In order to study the control function of slit to vortex flow field the influenceof slit width on flow properties was calculated. By analyzing the fluid flow status inslit, flow relationship between vortex frequency and velocity, pressure loss andvortex geometrical characteristic an optimal slit width was given.4、The experimental system of vortex flowmeter was constructed. The hardwareand software design of vortex signal detection were finished as well and vortex signal acquisition function was realized. Vortex signal characteristics of circularcylinder with different slit width and circular cylinder and trapezoidal cylinder werestudied. Series parameters such as vortex frequency, the relationship between St andRe, the intensity of vortex signal, signal to noise ration and pressure loss wereextracted in order to explain the feasibility of circular cylinder with a slit applying tovortex flowmeter. This study provides reference for bluff body optimization andperformance enhancement of vortex flowmeter.