Aerofoil Surface Pressure Reconstruction from Far-Field Array Measurements

2018 ◽  
Author(s):  
Fabio Casagrande Hirono ◽  
Phillip Joseph ◽  
Filippo Maria Fazi
Keyword(s):  
Surface Pressure ◽  
Far Field ◽  
Array Measurements

Surface pressure fluctuations on aircraft flaps and their correlation with far-field noise

2000 ◽  
Vol 415 ◽  
pp. 175-202 ◽  
Author(s):  
Y. P. GUO ◽  
M. C. JOSHI ◽  
P. H. BENT ◽  
K. J. YAMAMOTO
Keyword(s):  
Surface Pressure ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Dominant Frequency ◽  
Vortex Structures ◽  
Far Field ◽  
Mean Flow ◽  
Noise Sources ◽  
Side Edge ◽  
Field Noise

This paper discusses unsteady surface pressures on aircraft flaps and their correlation with far-field noise. Analyses are made of data from a 4.7% DC-10 aircraft model test, conducted in the 40 × 80 feet wind tunnel at NASA Ames Research Center. Results for various slat/wing/flap configurations and various flow conditions are discussed in detail to reveal major trends in surface pressure fluctuations. Spectral analysis, including cross-correlation/coherence, both among unsteady surface pressures and between far-field noise and near-field fluctuations, is used to reveal the most coherent motions in the near field and identify potential sources of noise related to flap flows. Dependencies of surface pressure fluctuations on mean flow Mach numbers, flap settings and slat angles are discussed. Dominant flow features in flap side edge regions, such as the formation of double-vortex structures, are shown to manifest themselves in the unsteady surface pressures as a series of spectral humps. The spectral humps are shown to correlate well with the radiated noise, indicating the existence of major noise sources in flap side edge regions. Strouhal number scaling is used to collapse the data with satisfactory results. The effects of flap side edge fences on surface pressures are also discussed. It is shown that the application of fences effectively increases the thickness of the flaps so that the double-vortex structures have more time to evolve. As a result, the characteristic timescale of the unsteady sources increases, which in turn leads to a decrease in the dominant frequency of the source process. Based on this, an explanation is proposed for the noise reduction mechanism of flap side edge fences.

Measuring Surface Pressure with Far Field Acoustics

2009 ◽  
Author(s):  
William Devenport ◽  
Elisabeth Wahl ◽  
Stewart Glegg ◽  
William Alexander ◽  
Dustin Grissom
Keyword(s):  
Surface Pressure ◽  
Far Field ◽  
Measuring Surface

Experimental and Unsteady Numerical Investigation of the Tip Clearance Noise of an Axial Fan

2013 ◽  
Author(s):  
Tao Zhu ◽  
Thomas H. Carolus
Keyword(s):  
Surface Pressure ◽  
Temporal Structure ◽  
Pressure Fluctuations ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Far Field ◽  
Axial Fan ◽  
Clearance Ratio ◽  
Wall Pressure Fluctuations ◽  
Unsteady Surface Pressure

The aerodynamic and aeroacoustic performance of axial fans are strongly affected by the unavoidable tip clearance. Two identical fan impellers but with different tip clearance ratio were investigated. Unsteady wall pressure fluctuations in the tip region of the rotating blades and on the interior wall of the duct type shroud and the overall sound radiated were analysed by an unsteady numerical Scale-Adaptive Simulation (SAS) and unsteady surface pressure measurements in both, the stationary and rotating system. Based on SAS-predicted pressure fluctuations on the blade surfaces the acoustic analogy according to Ffowcs Williams and Hawkings (FWH) was employed to calculate the sound pressure in the far field. In general, experimentally and numerically determined unsteady flow were found to be a tendentially good agreement. The spatial and temporal structure of the tip vortex system and the resulting unsteady pressure distribution on the surfaces in the vicinity of the blade tips was revealed in good detail. The vortices’ strength and trajectories as well as the unsteadiness are controlled by the size of the tip clearance and the operating point: As tip clearance is increased blade/vortex interaction becomes more prevalent and with it the unsteady surface pressure and eventually the sound radiated into the far field. The broadband tip clearance noise was acceptably predicted from the simulation results, while the prediction at discrete frequency should still be improved in the further work.

Measuring surface pressure with far field acoustics

2010 ◽  
Vol 329 (19) ◽  
pp. 3958-3971 ◽  
Author(s):  
William Devenport ◽  
Elisabeth A. Wahl ◽  
Stewart A.L. Glegg ◽  
W. Nathan Alexander ◽  
Dustin L. Grissom
Keyword(s):  
Surface Pressure ◽  
Far Field ◽  
Measuring Surface

Array Measurements of the Unsteady Surface Pressure in a Sharp-Edged Impinging Jet

2010 ◽  
Author(s):  
William Jiang ◽  
Ke Zhang ◽  
Ahmed Naguib ◽  
Moahmed El-Anwar ◽  
AbdelAziz Abouel-Fotouh
Keyword(s):  
Surface Pressure ◽  
Impinging Jet ◽  
Array Measurements ◽  
Unsteady Surface Pressure

scholarly journals Direct numerical simulation of turbulent flow past a trailing edge and the associated noise generation

2008 ◽  
Vol 596 ◽  
pp. 353-385 ◽  
Author(s):  
RICHARD D. SANDBERG ◽  
NEIL D. SANDHAM
Keyword(s):  
Turbulent Flow ◽  
Surface Pressure ◽  
Pressure Difference ◽  
Acoustic Pressure ◽  
Three Dimensional ◽  
Far Field ◽  
Noise Generation ◽  
Reasonable Accuracy ◽  
Dimensional Theory ◽  
Trailing Edge

Direct numerical simulations (DNS) are conducted of turbulent flow passing an infinitely thin trailing edge. The objective is to investigate the turbulent flow field in the vicinity of the trailing edge and the associated broadband noise generation. To generate a turbulent boundary layer a short distance from the inflow boundary, high-amplitude lifted streaks and disturbances that can be associated with coherent outer-layer vortices are introduced at the inflow boundary. A rapid increase in skin friction and a decrease in boundary layer thickness and pressure fluctuations is observed at the trailing edge. It is demonstrated that the behaviour of the hydrodynamic field in the vicinity of the trailing edge can be predicted with reasonable accuracy using triple-deck theory if the eddy viscosity is accounted for. Point spectra of surface pressure difference are shown to vary considerably towards the trailing edge, with a significant reduction of amplitude occurring in the low-frequency range. The acoustic pressure obtained from the DNS is compared with predictions from two- and three-dimensional acoustic analogies and the classical trailing-edge theory of Amiet. For low frequencies, two-dimensional theory succeeds in predicting the acoustic pressure in the far field with reasonable accuracy due to a significant spanwise coherence of the surface pressure difference and predominantly two-dimensional sound radiation. For higher frequencies, however, the full three-dimensional theory is required for an accurate prediction of the acoustic far field. DNS data are used to test some of the key assumptions invoked by Amiet for the derivation of the classical trailing-edge theory. Even though most of the approximations are shown to be reasonable, they collectively lead to a deviation from the DNS results, in particular for higher frequencies. Moreover, because the three-dimensional acoustic analogy does not provide significantly improved results, it is suggested that some of the discrepancies can be attributed to the approach of evaluating the far-field sound using a Kirchhoff-type integration of the surface pressure difference.

scholarly journals Acoustic source distribution on aerofoils and its reconstruction from far-field array measurements

2021 ◽  
Vol 492 ◽  
pp. 115786
Author(s):  
Fabio Casagrande Hirono ◽  
Phillip F. Joseph ◽  
Filippo M. Fazi
Keyword(s):  
Source Distribution ◽  
Far Field ◽  
Acoustic Source ◽  
Array Measurements

Array measurements of the surface pressure beneath a forced axi-symmetric separation bubble

2008 ◽  
Vol 46 (2) ◽  
pp. 297-308 ◽  
Author(s):  
Antonius Aditjandra ◽  
Barry J. Trosin ◽  
Ahmed M. Naguib
Keyword(s):  
Surface Pressure ◽  
Separation Bubble ◽  
Array Measurements ◽  
Symmetric Separation
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