Measurements of a 2-D non-buoyant jet in a wave environment

Abstract

This paper considers the dispersion of a 2-D non-buoyant jet discharged beneath a series of progressive gravity waves. A new experimental investigation is described in which the dispersion of a jet in a wave environment is compared to an identical discharge in a stagnant ambient. This comparison highlights the additional wave-induced mixing and shows that the oscillatory wave motion has a significant effect upon both the mean velocity profiles and the magnitude of the turbulent fluctuations. In particular, the experimental data suggests that the wave motion encourages a transfer of energy into the turbulent components of the flow field. This effect is most pronounced within the “zone of flow establishment”, and leads to a significant increase in the effective Reynolds stresses. This in turn creates a region of intense fluid mixing which is characterised by a large reduction in the axial velocity components and a substantial increase in the rate of entrainment. The experimental data is also compared to both the existing integral solutions and a Lagrangian formulation which is similar to that proposed by Chin (1988). Although neither of these solutions is able to model the flow immediately downstream of the outlet, the Lagrangian solution provides an improved description of the mean velocity within the “zone of established flow”.