  Buoyancy effects and nozzle geometry can have a significant impact on
turbulent jet dispersion. This work was motivated by applications involving
hydrogen. Using helium as an experimental proxy, buoyant horizontal jets
issuing from a round orifice on the side wall of a circular tube were analysed
experimentally using particle image velocimetry (PIV) and planar laser-induced
fluorescence (PLIF) techniques simultaneously to provide instantaneous and
time-averaged flow fields of velocity and concentration. Effects of buoyancy
and asymmetry on the resulting flow structure were studied over a range of
Reynolds numbers and gas densities. Significant differences were found between
the centreline trajectory, spreading rate, and velocity decay of conventional
horizontal round axisymmetric jets issuing through flat plates and the pipeline
leak-representative jets considered in the present study. The realistic
pipeline jets were always asymmetric and found to deflect about the jet axis in
the near field. In the far field, it was found that the realistic pipeline leak
geometry causes buoyancy effects to dominate much sooner than expected compared
to horizontal round jets issuing through flat plates.
