Vortex interactions in an axisymmetric water jet

Abstract

An axially symmetric water jet was designed and constructed to complement an existing air jet facility. The water jet operates at Reynolds numbers, based on nozzle diameter, up to 50,000. The jet is forced at high levels by a reciprocating Scotch yoke mechanism. By using an output signal from the Scotch yoke as a phase reference, it is possible to obtain either phase-locked hot film data or phase-locked photographs of the dye-marked coherent vortical structures in the shear layer. By assuming zero azimuthal velocity, continuity allows reconstruction of the vorticity field from the data obtained traversing the jet using a single straight hot film probe. Thus the phase-locked photographs and the phase-locked data sets can be compared. The close agreement of the reconstructed vorticity with the photographs gives credence to the assumption of zero azimuthal velocity, and shows that the dye injection method of flow visualization accurately represents the vortical structure of this flow.