Introduction

At the very beginning of this book, the concept of wave–mode duality was emphasised. Its importance to engineering noise and vibration analysis will be illustrated in this chapter via a specific case study relating to pipe flow noise.

The general subject of flow-induced noise and vibrations is a large and complex one. The subject includes: (i) internal axial pipe flows – the transmission of large volume flows of gases, liquids or two phase mixtures across high pressure drops through complex piping systems comprising bends, valves, tee-junctions, orifice plates, expansions, contractions, etc.; (ii) internal cross-flows in heat exchangers, etc. with the associated vortex shedding, acoustic resonances and fluid-elastic instabilities; (iii) external axial and cross-flows – e.g. vortex shedding from chimney stacks; (iv) cavitation; and (v) structure-borne sound associated with some initial aerodynamic type excitation. The reader is referred to Naudascher and Rockwell, a BHRA (British Hydromechanics Research Association) conference publication and Blake for discussions on a wide range of practical experiences with flow-induced noise and vibrations.

This chapter is, in the main, only concerned with the study of noise and vibration from steel pipelines with internal gas flows – this noise and vibration is flow-induced and is of considerable interest to the process industries. There are many instances of situations where flow-induced noise and vibration in cylindrical shells have caused catastrophic failures. The mechanisms of the generation of the vibrational response of and the external sound radiation from pipes due to internal flow disturbances are discussed in this chapter.