Numerical Analysis and Optimization on Vortex Shedder by the Linearity of Strouhal Number against Reynold Number

Abstract—The design parameters and blockage ratio of the bluff body called vortex shedder of the vortex flowmeter strongly influence on the flowmeter performance. The released frequency only depends on the size of vortex shedder and flow rate of fluid while independent of the fluid properties. In the condition of constant Strouhal number, the flowmeter is not affected by the properties such as temperature or pressure of measuring fluids. Thus, optimization a flowmeter design by considering the linearity of Strouhal number against the Reynold number becomes one of the ideas of designing the flowmeter. In the present work, the unsteady flow past a bluff body of diamond-shape with slit has been carried out to analysis on the Strouhal number using FLUENT, a CFD code. The numerical analysis was conducted for non-circular cross-section pipe of 7.457mm hydraulic diameter in the Reynold number range of 2400 to 60000. The blockage ratio from 0.16 (about 1/6) to 0.30 (about 1/3) were considered and for the slit ratio, 0.10-0.16 were used. We took only three angle, 45o, 60o, and 90o for this work as longer and more slender shedding bodies result in weaker and less coherent shedding. The optimized design was achieved by the linearity of Strouhal number against Reynold number. And, the linearity is determined by the error percentage of Strouhal number. According to the results, it has been found that the bluff body with the parameters of 0.24 blockage ratio, 0.14 slit ratio and 60o apex angle is the best design.

Index Terms—Linearity of Strouhal number against Reynold number, diamond-shape with slit, non-circular cross-section pipe, numerical analysis.

The authors are with the College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin, 150001, P.R. China (e-mail: sumyatnyein.me@gmail.com, railway_dragon@sohu.com).

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Cite: Su Myat Nyein and He Xu, "Numerical Analysis and Optimization on Vortex Shedder by the Linearity of Strouhal Number against Reynold Number," International Journal of Materials, Mechanics and Manufacturing vol. 4, no. 3, pp. 204-207, 2016.