Experimental and Numerical Investigation of Turbulent Jets Issuing Through a Realistic Pipeline Geometry: Asymmetry Effects for Air, Helium, and Hydrogen

TL;DR

This study combines experiments and simulations to analyze how realistic pipe-issuing turbulent jets of air, helium, and hydrogen behave, revealing asymmetries and effects of buoyancy that impact gas dispersion predictions.

Contribution

It provides new insights into the asymmetry and buoyancy effects of realistic turbulent jets from pipes, improving understanding beyond traditional round jet models.

Findings

Jets are asymmetric and deflect about the vertical axis.

Heavier gases cause more deflection due to buoyancy.

Realistic jets decay faster and spread asymmetrically compared to ideal round jets.

Abstract

Experiments and numerical simulations were conducted to investigate the dispersion of turbulent jets issuing from realistic pipe geometries. The effect of jet densities and Reynolds numbers on vertical buoyant jets were investigated, as they emerged from the side wall of a circular pipe, through a round orifice. Particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques were employed simultaneously to provide time-averaged flow velocity and concentrations fields. Large eddy simulation (LES) was applied to provide further detail with regards to the three-dimensionality of air, helium, and hydrogen jets. These realistic jets were always asymmetric and found to deflect about the vertical axis. This deflection was influenced by buoyancy, where heavier gases deflected more than lighter gases. Significant turbulent mixing was also observed in the near field. The realistic jets, therefore, experienced faster velocity decay, and asymmetric jet spreading compared to round jets. These findings indicate that conventional round jet assumptions are, to some extent, inadequate to predict gas concentration, entrainment rates and, consequently, the extent of the flammability envelope of realistic gas leaks.