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Vortex sound

Abstract

One of the concerns with Lighthill's analogy is the physical interpretation of the source term Tij and relating it to easily recognized features of the flow. In many cases the flow may include relatively large coherent structures that are characterized by almost two-dimensional line vortices. Examples include coherent vortex shedding behind a cylinder or into a wake, and tip vortices interacting with helicopter rotor blades. These problems are often more readily understood if the sound is related to the vorticity in the flow rather than the Lighthill stress tensor. In this chapter we review the theory of vortex sound and give some examples of its application in low Mach number flows. In particular we will consider ...

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