Effect of Streamwise Vortices on Characteristics of Jets(<Special Issue>Jets, Wakes and Separated Flows)

The interaction of streamwise and axisymmetric vortices in an axisymmetric jet is studied by flow visualization and velocity measurement. The jet is excited by azimuthal and axial perturbations to enhance streamwise and axisymmetric vortices. The three-dimensional views of the jet-boundary surface and streamwise vortices are constructed by applying the Taylor hypothesis to the jet cross-sectional images, and the interaction model of streamwise and axisymmetric vortices is proposed. The interaction of spanwise and streamwise vortices in a plane jet is also studied by velocity measurement. The experiment is carried out under conditions similar to those of the axisymmetric jet. The vortical structure is discussed on the basis of the three-dimensional views of phase-averaged vorticities. It is confirmed that the interacting vortical structure is similar to that in an axisymmetric jet. The entrainment mechanism is also discussed in relation to the vortical structure.