Issue
Acta Acustica Volume 97, Issue Number 1, 2011
Number of page(s)10
DOIhttps://doi.org/10.3813/AAA.918383
 
 
 
On the Use of Linear Acoustic Multiports to Predict Whistling in Confined Flows
 
 
  • Mikael Karlsson
  • Mats Åbom
 
 
Abstract
The use of linear acoustic multiport models to analyse the existence of flow driven instabilities, that is – self-sustained oscillators or whistles – is addressed. By combining the scattering and reflection matrices for a system and searching for eigenfrequencies (zeros) in the critical half-plane, the existence of exponentially growing instabilities can be determined. In practice, the available frequency domain data are only known along the real axis; then the search for zeros may be done via the so-called Nyquist stability criterion generalized to an N-degree of freedom system. The method has been validated by two test cases, a T-junction and a Herschel-Quincke tube. In both cases, the occurrence and the frequencies of the self-sustained oscillations were correctly predicted.