Screech characteristics during mode change in underexpanded circular pipe jet

The screeching characteristics of an underexpanding cold jet emerging from circular pipe nozzles are discussed in detail. Two screech modes were observed at higher pressure ratios, namely the Mode D and Mode C respectively. The focus is emphasized during the modal change of these screech tones. It is fascinating to understand that, there is a permanent phase shift between the Modes D and C, subsequent to the modes change. This aspect has been analyzed and reported by making phase plots between the acoustic signals obtained for these two screech modes.