A Computational Fluid Dynamics Study on Characteristics of Flow Separation in Flow Rate Measurement Using Multi-Hole Plates †

Abstract

Flow rate measurement is a challenging task in the industry as there is no general-purpose measuring instrument for all appliances. However, orifice plates with multiple holes can be employed to measure the flow rate accurately. A computational fluid dynamics (CFD)-based numerical study was conducted to investigate the flow separation characteristics caused by the flow of water in multiple-hole orifice plates using ANSYS FLUENT R15.0 software. The study included single- and multiple-hole orifice plates, with orifices with a 36% area ratio, an equivalent diameter ratio (β-ratio) of 0.6, and hole number configurations of 1H, 4H, 9H, 16H, and 25H. The discharge coefficient for flow through multiple-hole orifices was obtained and compared for holes distributed in circular and square configurations. The significant parameters considered for the analysis were the hole number, distribution of holes, pressure drop, and reattachment points. A k-ε turbulence model was employed to study velocity fields, reattachment length, and discharge coefficient. We discuss the effects of hole numbers and their allocation on the reattachment length and discharge coefficient. Results are presented in the form of pressure variation comparisons, downstream recovery distance plots, recirculation zone plots, and percentage change in the coefficient of discharge. The study revealed that the number of holes in the plate significantly affects the pressure drop across the plate, the recirculation zone, and the orifice’s discharge coefficient.