Abstract
Flow-induced acoustic resonance in the closed side branch of a natural gas pipeline can cause intensive vibration which threatens the safe operation of the pipeline. Accurately modeling this excitation process is necessary for a workable understanding of the genetic mechanism to resolve this problem. A realizable k-ε Delayed Detached Eddy Simulation (DDES) model was conducted in this study to numerically simulate the acoustic resonance problem. The model is shown to accurately capture the acoustic resonance phenomenon and self-excited vibration characteristics with low calculation cost. The pressure pulsation component of the acoustic resonance frequency is gradually amplified and transformed into a narrowband dominant frequency in the process of acoustic resonance excitation, forming a so-called “frequency lock-in phenomenon.” The gas is pressed into and out of the branch in sinusoidal mode during excitation. The first-order frequency, single vortex moves at the branch inlet following the same pattern. A quarter wavelength steady standing wave forms in the branch. The mechanism and characteristics presented in this paper may provide guidelines for developing new excitation suppression methods.
Highlights
Natural gas is a clean, efficient, and high-quality energy resource which is a preferred fuel by many countries across the globe [1, 2]. e mileage of natural gas pipeline construction projects has rapidly increased alongside the demand for fuel in recent decades
E mean flow kinetic energy in the main pipeline provides constant energy for the system. e closed side branch structure is a regulator. e acoustic particles in the pipe are the main vibration body. e pressure fluctuation in the closed side branch is fed back to the regulator to control the continuity of the fluctuation. e flow-induced acoustic resonance has self-excited vibration characteristics, so a self-excited vibration model was used in this study
All of these cases were initialized from the inlet of the main pipe at the corresponding velocity and were calculated until a stable acoustic resonance formed. e acoustic resonance excitation process initially attenuated at various flow velocities, presenting cluttered signals. e difference was whether acoustic resonance formed
Summary
Natural gas is a clean, efficient, and high-quality energy resource which is a preferred fuel by many countries across the globe [1, 2]. e mileage of natural gas pipeline construction projects has rapidly increased alongside the demand for fuel in recent decades. Ziada [19], for example, found that the mechanism of acoustic resonance is different from that of nonresonant oscillation of impact shear flow; visual analysis revealed that pressure fluctuation in closed side branches was caused by the coupling of the unstable detachment of shear layer from the upstream wall and standing acoustic waves in the side branch. Radavich et al [27] briefly discussed the coupling of sound waves and flow in the excitation process and simulated the variations in pressure pulsation during excitation, but there has been no extensive research on the mechanism and excitation process of acoustic resonance Such knowledge has great significance in regards to establishing an accurate, descriptive model. E mean flow kinetic energy in the main pipeline provides constant energy for the system. e closed side branch structure is a regulator. e acoustic particles in the pipe are the main vibration body. e pressure fluctuation (acoustic standing wave) in the closed side branch is fed back to the regulator to control the continuity of the fluctuation. e flow-induced acoustic resonance has self-excited vibration characteristics, so a self-excited vibration model was used in this study
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