Laboratory modelling of a round jet in an unsteady crossflow

Abstract

We describe an experimental technique to investigate the effect of an oscillating crossflow on the dispersion of a turbulent round jet. A vertical jet-pipe-nozzle assembly is made to oscillate horizontally in the steady flow stream in a laboratory flume. To an observer moving with the assembly, the jet is issuing into a crossflow which consists of a mean current and a sinusoidally oscillating component. We use computer-aided flow visualisations to study the dispersion pattern and compare it with the pattern obtained by discharging a vertical jet into a horizontal flow with progressive shallow-water waves, a situation bearing a close similarity to a genuine oscillating flow with a non-zero mean velocity.