抄録
Whistler nozzle has a simple geometry, consisting of a constant diameter straight pipe nozzle and the sudden expansion of a collar which can slide over the pipe nozzle. With a certain sliding length of the collar, audible self-oscillation can be generated in the jet flow. This oscillatory excitation can enhance the entrainment of the surroundings and disturb the potential core of the jet. In the previous flow visualization experiment, comparison between the excited and non-excited cases revealed that the oscillation drastically modifies the vortical structures of the jet, which results in the change of the distribution patterns of the impingement heat transfer. In the present study, more detail experiments were made to see how the effects of oscillation frequency, jet velocity and impingement distance on the heat transfer distributions are. It was found that the jet flow structure changes with Strouhal number, most dominant parameter based on the frequency, and has great influence on the distributions. The transition of the distribution pattern in the case of the excited case was changed more quickly with an increase in the impinging distance, compared with the non-excited case.
