CFD investigation of flow through an orifice inside a pipe

Abstract

Flow measurement is found in a large variety of industries and for different types of fluids. Orifice flow meters are widely used for measuring the flow rate in pipelines due to its small size in the piping system and ability to output the flow rate with satisfying accuracy. The main problems with the orifice flow meter are the unrecoverable pressure loss and due to the shear forces exerted from the orifice walls onto the flow, inaccurate flow rate measurement as well as the vortex shedding behind the orifice. Numerical studies have been performed using the open source CFD code OpenFOAM to investigate the flow through a circular square edged orifice with various thicknesses and diameters inside a pipe. The orifice thickness to pipe diameter ratio (t) varies between 0.125 ≤ t ≤ 2 and the orifice diameter to pipe diameter (𝛽�) varies between 0.25 ≤ 𝛽� ≤ 0.75. The discharge coefficients for the different orifice characteristics at different Reynolds numbers have been determined. Simulations are performed in two different regimes, a laminar flow regime at 0 ≤ 𝑅�𝑒� ≤ 400 and a turbulent flow regime at 2 500 ≤ 𝑅�𝑒� ≤ 40 000. The effects of different 𝑅�𝑒�, 𝛽� and 𝑡� on the flow characteristics are discussed by presenting the streamwise velocity contours, streamlines and 𝑄�-criterion contours. The results of the present study have been compared with the previous published numerical and experimental results as the validation study. The discharge coefficients are in satisfying agreement with the previous published numerical and experimental data.