A method making use of the photoacoustic effect to control the formation of large scale structures in an axisymmetric ethylene jet at Reynolds numbers ranging between 2,000 and 2,550 is described. The experiment involved modulating the beam of a CO2 laser at Strouhal frequencies between 0.31 and 0.46 and focussing the beam into the gas jet. Time-averaged flow fields, perturbed with photoacoustic pulses are compared to that forced with a sinusoidal acoustic excitation and the results of a parametric study of the photoacoustic forcing are presented. Perturbations, achieved by laser heating the gas molecules are shown to force the flow into the jet-column fundamental and harmonic mode and to enhance vortex pairing. Time-averaged merging events at different phases of the process are displayed.
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Fourguette, D.C., Winter, M. Control of large-scale structure formation and vortex pairing using photoacoustic forcing. Experiments in Fluids 10, 157–160 (1990). https://doi.org/10.1007/BF00215024
- Reynolds Number
- Flow Field
- Parametric Study
- Scale Structure