A theoretical and experimental study of the velocity distribution and transition to turbulence in free oscillatory flow

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Abstract
The free oscillatory flow of a viscous fluid in a U-shaped tube is considered. A theoretical analysis (in which an axial flow is assumed and the start-up of the column is taken into account) shows, depending on the value of the similarity parameter γ, various regimes of the flow. Measurements of the velocity distribution are made using hot-film velocity probes, operated with a constant-temperature anemometer, and visualizations of the flow are performed. Experimental results are in good agreement with theoretical ones when the flow is laminar, and show the possible existence of turbulent flows. Critical values, at which the flow is disturbed over a more or less extended range of the successive oscillations, are determined for the similarity parameters γ and h0/R.