Normal incidence acoustic insertion loss of perforated plates with bias flow

2015 ◽  
Vol 138 (6) ◽  
pp. 3907-3921 ◽  
Author(s):  
Vincent Phong ◽  
Dimitri Papamoschou
Keyword(s):  
Insertion Loss ◽  
Normal Incidence ◽  
Perforated Plates ◽  
Bias Flow

A Novel Design Method for Robust Acoustic Dampers With Perforated Plates Backed by a Cavity Operating at Low and High Strouhal Numbers

2012 ◽  
Author(s):  
A. Scarpato ◽  
S. Ducruix ◽  
T. Schuller
Keyword(s):  
Flow Velocity ◽  
Design Method ◽  
Resonant Cavity ◽  
Plate Thickness ◽  
Optimization Procedure ◽  
Absorption Frequency ◽  
Perforated Plates ◽  
Peak Absorption ◽  
Bias Flow ◽  
Optimal Bias

It is known that the frequency of thermo-acoustic instabilities may vary according to various parameters during operation. The design of passive acoustic dampers tuned to damp specific unstable frequencies must then include this aspect to offer robust properties. This problem is tackled here for perforated plates backed by a resonant cavity in the absence of grazing flow. Their current design relies on a relatively complex optimization procedure with a large number of parameters to examine. A new methodology is proposed to reduce this number by finding the optimal parameters maximizing absorption in two limit regimes, where the choice of the optimal bias flow velocity and size of the back cavity can be decoupled. The former is only controlled by the plate porosity while the latter fixes the peak absorption frequency. The analysis also includes effects of the plate thickness. In both regimes, the optimal bias flow velocity is analytically determined. A Helmholtz resonance and a narrow absorption peak in the frequency space characterize the first absorption regime reached at high Strouhal numbers. This regime minimizes the size of the resonant back cavity, but the absorption frequency bandwidth narrows with increasing Strouhal numbers. The second absorption regime reached at low Strouhal numbers operates with a quarter-wave resonator. This regime requires larger cavity depths but offers a wider absorption bandwidth around the peak absorption frequency well suited for low frequency dampers when the bias flow velocity or the unstable frequency may vary within the system. Theoretical predictions are validated against experimental data obtained in the two regimes identified. The expressions derived in this study can be used to improve the design of robust acoustic dampers.

EFFECT OF GRAZING–BIAS FLOW INTERACTION ON ACOUSTIC IMPEDANCE OF PERFORATED PLATES

2002 ◽  
Vol 254 (3) ◽  
pp. 557-573 ◽  
Author(s):  
X. SUN ◽  
X. JING ◽  
H. ZHANG ◽  
Y. SHI
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Flow Interaction ◽  
Bias Flow

Ultrasonic airborne insertion loss measurements at normal incidence (L)

2010 ◽  
Vol 128 (6) ◽  
pp. 3305-3307 ◽  
Author(s):  
Jayrin Farley ◽  
Brian E. Anderson
Keyword(s):  
Insertion Loss ◽  
Normal Incidence
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