Discussion of “Flow Excited Acoustic Resonance Excitation Mechanism, Design Guidelines and Counter Measures,†(Ziada, S., and Lafon, P., 2014, ASME Appl. Mech. Rev., 66(1), p. 010802)
Abstract
The authors have done extensive research in gathering historical background on the subject of flow excited acoustic resonance. They have provided extensive discussion to justify creative formulations for predicting the onset of resonance and estimating the associated maximum pressure amplitudes. Their approach makes use of reported experimental studies plus some of their own to make charts that should be useful for some common industrial problems. An independent scaling approach is offered in this review to verify the dominant parameters and variables employed by the authors in their predictive methods. It was found that for low Mach number flows, a specific Reynolds number (Re) dependence was missing. However, since it is known that the Strouhal dependence is very weak on Reynolds numbers up to about 105, the absence of specific Re dependence is probably inconsequential. Another concern was that interaction between the acoustics and vortex shedding or shear layer instabilities could affect the eigenfrequencies. A simple model showed that this is possible, but Quad Cities experience cited by the authors indicated one case where it was not important. The RollsRoyce Vertical Lift System example with coaxial closed sidebranches could have had a significant interaction with the annular liquid mass on eigenmodes. The mass effect resulting from the annular space connecting both branches could act less like an oscillating shear layer and more like a Helmholtz resonator. This could have a significant effect on the natural frequency of either or both branch pipes. Although that effect is not specifically considered here, if it was significant, it would be naturally embraced in a scale model based on the scaling laws presented in this review.