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Research Papers: Fluid-Structure Interaction

On the Modelling of Noise Generation in Corrugated Pipes

[+] Author and Article Information
Hugh Goyder

 Cranfield University, Shrivenham, Swindon SN6 8LA, UKh.g.d.goyder@cranfield.ac.uk

J. Pressure Vessel Technol 132(4), 041304 (Jul 21, 2010) (7 pages) doi:10.1115/1.4001977 History: Received October 30, 2009; Revised June 02, 2010; Published July 21, 2010; Online July 21, 2010

The offshore oil and gas industry uses corrugated pipes because of their flexibility. Gas flowing within these pipes interacts with the corrugations and generates noise. This noise is of concern because it is of sufficient amplitude to cause pipework vibration with the threat of fatigue and pipe breakages. This paper examines the conditions that give rise to the large noise levels. These conditions, for the occurrence of noise, are investigated using an eigenvalue approach, which involves the effect of damping due to losses from the pipe boundaries and pipe friction. The investigation is conducted in terms of reflection conditions and shows why only few of the very many possible natural frequencies are selected. The conditions for maximum noise response are also investigated by means of a nonlinear model of vortex shedding. Here, an approach is developed in which the net power generated by each wavelength is calculated.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Construction of corrugated pipe: (1) antifriction layer, (2) outer layer of tensile armor, (3) antiwear layer, (4) inner layer of tensile armor, (5) back-up pressure armor, (6) interlocked pressure armor, (7) internal pressure sheath, and (8) carcass

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Figure 2

Corrugated pipe carcass showing cavity and shear layer

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Figure 3

Diagrammatic representation of pipe, flow, cavities, and shear layers. The sources from the cavities can be either monopoles (shown as straight arrows) or dipoles (shown as curved arrows).

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Figure 4

A corrugated pipe of length L and cross-sectional area S operates between a side branch of length L1 and cross-sectional area S1 and a T-junction where the pipe cross-sectional area changes to S2.

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Figure 5

Modulus of reflection coefficient for a side branch plotted on logarithmic scale. Here, the area ratio S1/S=0.1 and L1 is the length of the side branch. The peaks in the reflection coefficient coincide with resonances in the side branch.

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Figure 6

Complex natural frequencies (poles) of system in Fig. 4 with L/L1=100, S1/S=0.1, and S2/S=2. The horizontal axis is the real part of the natural frequency and the vertical axis is the imaginary part.

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Figure 7

A cavity with a shear layer. (a) The shear layer produces a monopole source with fluid pumped pistonlike into and out of the cavity. (b) A dipole source with the shear layer flapping in a hingelike manner.

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Figure 8

The nondimensional acoustic impedance of a shear layer from Graf and Ziada. The real part is shown on the horizontal axis while the imaginary part is shown vertically. The “spiral” lines correspond to constant acoustic amplitude normalized by flow velocity. The “radial” lines correspond to constant Strouhal numbers. Part (a) includes smaller acoustic amplitudes only while part (b) includes larger acoustic amplitudes.

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Figure 9

Real part of acoustic impedance of a shear layer for a Strouhal number of 0.4 as a function of acoustic velocity u divided by mean flow velocity U0. The function f(St,u/U0) is obtained, together with the points from Fig. 8. The smooth curve is a fit of Eq. 16 to this data.

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Figure 10

(a) The normalized acoustic velocity of a wave with 100 cavities in one wavelength. (b) The power generated by each cavity for the conditions of maximum power. (c) Saturated conditions where the positive power from sources is balanced by power absorbed in sinks. The cavity power is given as a percentage of the maximum total power that can be produced in one wavelength.

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