Affiliations: Department of Environmental Science and Technology,
Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan. E-mail:
shouiio@shinshu-u.ac.jp | Graduate School of Environmental Science and
Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan | Nagano National College of Technology, 716 Tokuma,
Nagano 381-8550, Japan
Abstract: Pulsating jet is visualized using hydrogen bubble method to clarify
the vortex nature in the near field of the jet. This study focused on the
development in space and time of vortex structures evolution in low
aspect-ratio rectangular jet with pulsation. Pulsation means large-amplitude,
low-frequency excitation which is expected to increase the mixing and spreading
of the jet and to accelerate its transition from a rectangular form to an
axisymmetric form. It was deemed appropriate to investigate whether jet
characteristics of a pulsating, submerged jet flow can be altered by including
pulsations. The difference of the vortex deformation process is discussed in
relation to pulsating conditions. Consequently, the pulsation leads to the
formation of vortices at regular intervals, which are larger than those
occurring in a steady jet. The results show that the streamwise interaction,
between leading vortex and trailing vortex rolled up at nozzle lips,
strengthens with increasing pulsating frequency. The spanwise drift of the
vortex becomes strongly apparent at large amplitude and high frequency
conditions. The drifting start position does not change regardless of pulsating
condition. The convection velocity of vortex increases at lower frequency and
larger amplitude.
