Unsteady Flow Distortion Past Blades: Sources of Noise Generation in Rotating Flows

1992 ◽  
Author(s):  
D. O. Rockwell ◽  
O. Akin ◽  
J. H. Kim ◽  
S. Konak ◽  
J. Kuryla ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Rotating Flows ◽  
Noise Generation ◽  
Flow Distortion

scholarly journals Assessment methods for unsteady flow distortion in aero-engine intakes

2018 ◽  
Vol 72 ◽  
pp. 292-304 ◽  
Author(s):  
Daniel Gil-Prieto ◽  
David G. MacManus ◽  
Pavlos K. Zachos ◽  
Abian Bautista
Keyword(s):  
Unsteady Flow ◽  
Assessment Methods ◽  
Flow Distortion ◽  
Aero Engine

Investigation of the Unsteady Flow and Noise Generation in a Slat Cove

AIAA Journal ◽  
2016 ◽  
Vol 54 (2) ◽  
pp. 469-489 ◽  
Author(s):  
M. Terracol ◽  
E. Manoha ◽  
B. Lemoine
Keyword(s):  
Unsteady Flow ◽  
Noise Generation

Effects of Boundary Layer Ingestion on the Aero-Acoustics of Transonic Fan Rotors

2012 ◽  
Author(s):  
J. J. Defoe ◽  
Z. S. Spakovszky
Keyword(s):  
Boundary Layer ◽  
Parametric Study ◽  
Power Level ◽  
Sound Power ◽  
Far Field ◽  
Noise Generation ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Flow Distortion ◽  
Swirling Vortex

The use of boundary-layer-ingesting, embedded propulsion systems can result in inlet flow distortions where the interaction of the boundary layer vorticity and the inlet lip causes horseshoe vortex formation and the ingestion of streamwise vortices into the inlet. A previously-developed body-force-based fan modeling approach was used to assess the change in fan rotor shock noise generation and propagation in a boundary-layer-ingesting, serpentine inlet. This approach is employed here in a parametric study to assess the effects of inlet geometry parameters (offset-to-diameter ratio and downstream-to-upstream area ratio) on flow distortion and rotor shock noise. Mechanisms related to the vortical inlet structures were found to govern changes in the rotor shock noise generation and propagation. The vortex whose circulation is in the opposite direction to the fan rotation (counter-swirling vortex) increases incidence angles on the fan blades near the tip, enhancing noise generation. The vortex with circulation in the direction of fan rotation (co-swirling vortex) creates a region of subsonic relative flow near the blade tip radius which decreases the sound power propagated to the far-field. The parametric study revealed that the overall sound power level at the fan leading edge is set by the ingested streamwise circulation, and that for inlet designs in which the streamwise vortices are displaced away from the duct wall, the sound power at the upstream inlet plane increased by as much as 9 dB. By comparing the far-field noise results obtained to those for a conventional inlet, it is deduced that the changes in rotor shock noise are predominantly due to the ingestion of streamwise vorticity.

scholarly journals Novel Method for Evaluating Intake Unsteady Flow Distortion

2021 ◽  
pp. 1-13
Author(s):  
Matteo Migliorini ◽  
Pavlos K. Zachos ◽  
David G. MacManus
Keyword(s):  
Unsteady Flow ◽  
Flow Distortion ◽  
Novel Method

A Numerical Study on the Aeroacoustic of a Vaned Centrifugal Fan

2005 ◽  
Author(s):  
S. Khelladi ◽  
S. Kouidri ◽  
F. Bakir ◽  
R. Rey
Keyword(s):  
Unsteady Flow ◽  
High Speed ◽  
Numerical Study ◽  
Noise Generation ◽  
Centrifugal Fan ◽  
Home Appliances ◽  
Centrifugal Fans ◽  
Radial Forces ◽  
Return Channel ◽  
Dipole Sources

High speed vaned centrifugal fans are widely used in several manufacturing and home appliances. For the designers the noise generated by these machines is one of the most important parameters to be reduced. The centrifugal fan used for this study is made up of an impeller, a diffuser and a return channel. The impeller turns at a relatively high speed about 35000 rpm. The objective of this study is to understand the mechanism of the noise generation within this type of machines. The contribution of the tangential and radial forces is highlighted. These fluctuating forces are due to the unsteady flow at the impeller-diffuser interface. The obtained result shows the effect of monopole and dipole sources on the overall noise.

scholarly journals Effects of Boundary-Layer Ingestion on the Aero-Acoustics of Transonic Fan Rotors

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Jeffrey J. Defoe ◽  
Zoltán S. Spakovszky
Keyword(s):  
Boundary Layer ◽  
Parametric Study ◽  
Power Level ◽  
Sound Power ◽  
Far Field ◽  
Noise Generation ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Flow Distortion ◽  
Swirling Vortex

The use of boundary-layer-ingesting, embedded propulsion systems can result in inlet flow distortions where the interaction of the boundary-layer vorticity and the inlet lip causes horseshoe vortex formation and the ingestion of streamwise vortices into the inlet. A previously-developed body-force-based fan modeling approach was used to assess the change in fan rotor shock noise generation and propagation in a boundary-layer-ingesting, serpentine inlet. This approach is employed here in a parametric study to assess the effects of inlet geometry parameters (offset-to-diameter ratio and downstream-to-upstream area ratio) on flow distortion and rotor shock noise. Mechanisms related to the vortical inlet structures were found to govern changes in the rotor shock noise generation and propagation. The vortex whose circulation is in the opposite direction to the fan rotation (counter-swirling vortex) increases incidence angles on the fan blades near the tip, enhancing noise generation. The vortex with circulation in the direction of fan rotation (co-swirling vortex) creates a region of subsonic relative flow near the blade tip radius that decreases the sound power propagated to the far-field. The parametric study revealed that the overall sound power level at the fan leading edge is set by the ingested streamwise circulation, and that for inlet designs in which the streamwise vortices are displaced away from the duct wall, the sound power at the upstream inlet plane increased by as much as 9 dB. By comparing the far-field noise results obtained to those for a conventional inlet, it is deduced that the changes in rotor shock noise are predominantly due to the ingestion of streamwise vorticity.

Numerical Prediction of the Aerodynamic Tonal Noise in a Centrifugal Fan

2002 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria-Morros ◽  
Joaqui´n Ferna´ndez-Francos
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Experimental Investigations ◽  
Noise Generation ◽  
Centrifugal Fan ◽  
Tonal Noise ◽  
Interaction Phenomena

In this work, a numerical study about the aerodynamic tonal noise generation in an industrial centrifugal fan with backward curved blades has been carried out. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been performed. Special attention has been focused on the impeller-volute interaction phenomena, analysing the influence of the distance between the impeller and the volute tongue. The numerical results have been contrasted using previous experimental investigations carried out in the same machine.

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