An explanation for the phase lag in supersonic jet impingement. (14th February 2017)

• Record Type: Journal Article
• Authors: Weightman, Joel L.; Amili, Omid; Honnery, Damon; Soria, Julio; Edgington-Mitchell, Daniel
• Is Part Of: Journal of fluid mechanics. Volume 815(2017)
• Publication Date: 2017-02-14
• Subjects: aeroacoustics, -- flow–structure interactions, -- jet noise; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2017.37
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : For the first time, a physical mechanism is identified to explain the phase lag term in Powell's impinging feedback loop equation (Powell, J. Acoust. Soc. Am., vol. 83 (2), 1988, pp. 515–533). Ultra-high-speed schlieren reveals a previously unseen periodic transient shock in the wall jet region of underexpanded impinging flows. The motion of this shock appears to be responsible for the production of the acoustic waves corresponding to the impingement tone. It is suggested that the delay between the inception of the shock and the formation of the acoustic wave explains the phase lag in the aeroacoustic feedback process. This suggestion is quantitatively supported through an assessment of Powell's feedback equation, using high-resolution particle image velocimetry and acoustic measurements.