Line fountain behavior at low-Reynolds number

Abstract: In this paper, we present line fountain behavior at low-Reynolds numbers obtained by experiments. The experiments are conducted over the range of Reynolds number and Froude number . It is observed that the fountain behavior can be categorized broadly into four regimes: the steady; flapping; laminar mixing; and jet-type mixing behavior, at full development. The critical Froude number for transition from a steady to unsteady flow varies with the Reynolds number. For , the transition is independent of Re and is well described by the line. Over the range , the transition can be approximated by a constant line. For , there is a higher dependency on the Reynolds number with a very sharp increase in the critical Froude number and it is hypothesized that the demarcation line follows , where . The fountain exhibits flapping behavior in the range . These observed fountain behaviors are mapped on to a plot. In addition, the observed, non-dimensionalised fountain height is found to be in reasonable agreement with previous results on laminar line fountains. In particular, the experimental results confirm the scaling in the steady regime which was obtained previously by scaling analysis. [Copyright &y& Elsevier]