Numerical study of the oscillation amplitude effect on the heat transfer of oscillatory impinging round jets

Abstract

In this study, the effect of oscillation amplitude on the pulsed impinging jets in different nozzle to surface distances and Reynolds numbers investigated. Generally, the heat transfer increases by increasing frequency and amplitude. For distances smaller and longer than the length of the jet potential core the threshold frequency is highly dependent on the amplitude. As the amplitude increases, the threshold Strouhal number decreases, while for nozzle to surface distance near the end of the jet core the threshold Strouhal number is approximately independent from the oscillation amplitude and the Reynolds number and is about $Sr\approx 0.041.$ Also, although increasing the Reynolds number causes an enhancement in the threshold frequency, but in smaller amplitudes the heat transfer, increased relative to the corresponding steady jet.