Quantitative flow imaging approach to flow-acoustic coupling in pipeline-cavity systems

Abstract

This paper considers flow-induced pressure pulsations in engineering systems that involve a cavity mounted in a pipeline. These self-sustained oscillations pose substantial risk, as they can cause fatigue damage to the system and the associated acoustic pressure levels can be harmful to humans. This review focuses on experimental and semi-empirical methods of prediction of the acoustic response of pipeline-cavity systems, with specific emphasis on the description of the acoustic noise source and the interaction between the separated flow that exists in the vicinity of the cavity opening and three types of resonant acoustic modes that can be excited by the flow: longitudinal modes of the main pipeline, transverse modes of a side branch (deep cavity) and azimuthal modes of an axisymmetric cavity. Fundamental insight into the physical mechanism of excitation of the resonant acoustic modes provided by quantitative flow imaging is discussed. In particular, application of particle image velocimetry (PIV) for identifying and quantifying the features of the acoustic source is described for each type of the acoustic modes, along with the associated challenges and the limitations of applicability. Moreover, effects of the modifications of the system geometry on the acoustic response and the structure of the noise source are presented. The geometrical features considered in this paper include asymmetry of the main pipeline, splitter plates located in the vicinity of the opening of the cavity, and chamfers of the leading and the trailing edges of the cavity.

Keywords

• flow-induced noise
• acoustics
• pipelines
• cavity
• particle image velocimetry