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Updated: May 21, 2026

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
Published on: April 23, 2018
"Ladder" structure in tonal noise generated by laminar flow around an airfoil
Tze Pei Chong1, Phillip Joseph
1School of Engineering and Design, Brunel University, Uxbridge, UB8 3PH, United Kingdom. t.p.chong@brunel.ac.uk
Abstract:
The presence of a "ladder" structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the scattering of the boundary layer instability noise and the discrete noise produced by an aeroacoustic feedback loop.
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