SPOD analysis of noise-generating Rossiter modes in a slat with and without a bulb seal

Author(s)

Himeno, Fernando H. T. ^[1] ; Souza, Daniel S. ^[2] ; Amaral, Filipe R. ^{[3, 1]} ; Rodriguez, Daniel ^[4] ; Medeiros, Marcello A. F. ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Aeronaut Engn, Av Trabalhador Sao Carlense 400, BR-13566590 Sao Carlos, SP - Brazil

^[2] UNESP Sao Paulo State Univ, Av Profa Isette Correa Fontao 505, BR-13876750 Sao Joao Da Boa Vista, SP - Brazil

^[3] Aeronaut Inst Technol, Praca Marechal Eduardo Gomes 50, BR-12228900 Sao Jose Dos Campos, SP - Brazil

^[4] Univ Politecn Madrid, TSIAE UPM Sch Aeronaut, Plaza Cardenal Cisneros 3, Madrid 28040 - Spain

• Document type: Journal article
• Source: JOURNAL OF FLUID MECHANICS; v. 915, MAR 18 2021.
• Web of Science Citations: 0

Abstract

The slat represents an important airframe noise source as it extends over almost the entire aircraft wingspan. Most studies of slat noise consider idealized geometries. However, for practical applications, several elements are installed on its cove, such as bulb seals to avoid direct contact with the main wing surface. Previous investigations of an unswept and untapered MD30P3ON airfoil reported that the flow dynamics and the corresponding acoustic noise are very sensitive to the presence and location of the bulb seal. For certain locations a second recirculation bubble is created inside the slat cove and the acoustic narrowband peaks are intensified. The present paper shows that the two-bubble topology promotes the recirculation of turbulence within the slat cove. Spectral proper orthogonal decomposition analysis based on the radiated pressure intensity is used to identify the flow structures responsible for sound generation. Even though the recirculating turbulence is mostly incoherent, it interacts with the coherent Kelvin-Helmholtz vortices in the initial part of the mixing layer. Then, vortex merging and straining lead to the formation of complex vortex clusters. Our results show that the origin and evolution of these clusters are consistent with Rossiter's mechanism responsible for the narrowband peaks. The enhanced recirculation accelerates the cluster evolution leading to wider clusters and lower-frequency Rossiter modes. (AU)

• FAPESP's process: 16/02970-5 - Computational study of aeroacoustic effect of a seal located on slat cove and analysis by POD technique
• Grantee: Fernando Henrique Tadashi Himeno
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 06/52568-7 - Silent aircraft: a research on aeronautics
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Partnership for Technological Innovation - PITE
• FAPESP's process: 19/02203-2 - Study of inverse problems on turbulence and aeroacoustics employing the resolvent analysis
• Grantee: Filipe Ramos do Amaral
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/02542-9 - Numerical study of wave packets over a flat plate with roughness
• Grantee: Fernando Henrique Tadashi Himeno
• Support Opportunities: Scholarships in Brazil - Doctorate