Novel orifice plate flowmeter: Fractal design and jet characteristics

Fractal theory was introduced to design multi-hole orifice plates (MHOP), and a novel fractal orifice plate (FOP-G2) flowmeter was proposed. Computational fluid dynamics was used to investigate the measurement and jet characteristics of various orifice configurations. The results show that FOP-G2 has significantly superior measurement properties compared to conventional designs: lower pressure loss, higher differential pressure, and faster recovery. The pressure loss ratio of FOP-G2_5 was reduced by 5.27% compared to that of the single-hole orifice plate, and by 5%-10% compared to that of other MHOPs. These superior characteristics originate from the local merging and combined development of small-scale jets. The fractal configuration’s self-similarity creates self-similar jet structures. Among these, the local combined region (LMR) plays a key role in enabling rapid pressure recovery. The dimensionless LMR length using the generalized convergence diameter D c yields a constant λ = 0.126. The FOP-G2 jet displayed abundant small-scale columnar and circumferential vortex structures, inducing nonuniformity in the near-wall circumferential flowfield. Additionally, global jet oscillation instability in FOP-G2, due to the Kelvin-Helmholtz instability and Coanda effect, was observed, with the Strouhal number of jet oscillations increasing with larger D c .