The spreading rate of a single coflowing axisymmetric jet

The preliminary results of an experimental investigation into the behavior of a single jet in a coflowing ambient fluid are presented. The experimental results are compared with the predictions from two numerical models, one of which uses the centerline-velocity to define the spreading rate while the other uses the cross-sectional a verage-velocity for this task. The comparison of spread data with the model predictions indicates that the centerline velocity is the appropriate characteristic velocity in defining coflowing jet spread. However the dilution data departs from the centerline velocity model, which suggests that the turbulent fluxes may become more significant when approaching the transition region. Detailed experimental investigations into this problem are continuing.