Parametric investigation of the wake-vortex lock-in for the turbulent jet discharging from a stack Original Research Article

In an earlier paper we showed that for the case of a turbulent jet emitted from a stack into a crossflow, a lock-in between the jet-wake and the stack-wake vortices occurs. In this study, spectral analysis and a pattern-recognition technique in conjunction with multipoint hotwire measurements are used to investigate whether this lock-in is still maintained when the controlling flow parameters are significantly altered. It is found that the lock-in occurs over the whole range of jet-to-crossflow velocity ratios tested (1.5–6) and for the jet-to-stack diameter ratios as low as 0.63. At a jet-to-stack diameter ratio lying below about 0.5, however, the lock-in ceases to occur. Instead, jet-wake vortices appear at a Strouhal frequency based on the jet diameter.