Flow-induced noise of a wall-mounted finite airfoil at low-to-moderate Reynolds number

• Published in: Journal of sound and vibration Vol. 333; no. 25; pp. 6924 - 6941
• Main Authors: Moreau, Danielle J., Prime, Zebb, Porteous, Ric, Doolan, Con J., Valeau, Vincent
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.12.2014
• Subjects: Aerodynamics; Airfoils; Fluid dynamics; Fluid flow; Mathematical analysis; Noise; Reynolds number; Trailing edges
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1016/j.jsv.2014.08.005

This paper presents an experimental investigation of the flow-induced noise created by a wall-mounted finite airfoil at low-to-moderate Reynolds number and zero angle of attack. Far-field noise measurements have been taken at a single observer location and with two perpendicular microphone arrays in an anechoic wind tunnel at Reynolds numbers of Rec=9.2×104–1.6×105, based on chord, and for a variety of airfoil aspect ratios (length to chord ratio of L/C=0.2–2, corresponding to length to thickness ratio of L/T=1.7–16.7). Additionally, surface oil-film visualisation images and unsteady velocity measurements taken in the near trailing edge wake are related to far-field noise measurements to determine the flow mechanisms responsible for noise generation. The results show that the wall-mounted finite airfoil radiates noise similar to a two-dimensional airfoil when L/T>8.3. Despite the incoming boundary layer height at the junction being 1.30≤δ/T≤1.46, junction and tip flow suppresses tonal noise production for airfoil׳s up to L/T=8.3 at Rec=9.2×104–1.2×105. Trailing edge noise is found to be the dominant airfoil noise generation mechanism at frequencies above 1kHz with the position of the noise source along the trailing edge determined by the proportion of the airfoil span influenced by flow at the airfoil–wall junction.