Numerical Analysis of the Differential Flowmeter: Standard Orifice and Slotted Orifices

Abstract

The paper presents the results of simulation studies of fluid flow through a standard orifice and two slotted orifices. The research that has been carried out concerns the analysis of the effect of the orifice geometry on the velocity profiles, turbulence kinetic energy and turbulence energy dispersion. The profile studies were conducted at different distances behind the orifice so that the results could be compared with each other. The studied flow included an airflow whose inlet velocity was 15 m/s. The turbulence model k-ε was used for numerical calculations. The tested orifices were characterized by an orifice constriction equal to β = 0.5. The calculations involved flow through a pipeline with a diameter of 160 mm. The results show that for a standard orifice, the maximum velocity of the flow is about 95 m/s and this is recorded at a distance of about 10–20 cm behind the orifice, and then it decreases, and at a distance of about 60 cm, the flow velocity is about 27 m/s. In the case of slotted holes, the maximum velocity is about 30% lower compared to the flow rate through a standard orifice design. The maximum velocity behind slotted orifices occurs directly behind the orifice, and in the cases of slotted orifice 1 and slotted orifice 2, was about 70 m/s and 67 m/s, respectively. For slotted orifice 1, at a distance of 20 cm behind the orifice, the flow assumed a velocity of about 19 m/s, whereas for slotted orifice 2, the flow reached a speed of about 18 m/s, at a distance of about 30 cm behind the orifice. The values of the maximum kinetic energy of turbulence for the tested orifices are about 420 m2/s2 for the standard orifice, and about 250 m2/s2 and 220 m2/s2 for slotted orifices 1 and 2, respectively. The obtained simulation results demonstrated that slotted orifices lead to faster stream homogenization and do not disturb the flow as much as a standard orifice. Slotted orifices exhibit a higher flow coefficient.