M.Sc Thesis


M.Sc StudentVladimir Katz
SubjectEffect of Trailing Edge Elasticity on the Acoustic
Signature of an Airfoil in Unsteady Flow
DepartmentDepartment of Aerospace Engineering
Supervisor Assistant Professor Manela Avshalom


Abstract

Trailing edge noise is identified as a major component of airframe noise, particularly during airplanes approach for landing, when extensive use is made of high-lift devices. Consequently, significant efforts have been made to analyze the acoustic signature of these devices, in various setups and flight conditions. Common to almost all of these works is a consideration of a rigid lift device, in which the impacts of element geometry and orientation are examined.

The objective of the present work is to apply existing vibroacoustic methodologies to examine the effect of trailing edge elasticity on the acoustic radiation of an otherwise rigid airfoil. We consider the far-field radiation of a thin airfoil attached to a flexible downstream appendage, and compare it with radiation by a counterpart rigid structure. Flow unsteadiness is modeled as an incident line vortex, convected by the mean flow in the vicinity of the airfoil. Assuming low Mach and high Reynolds flight conditions, the near-field flow is examined based on thin-airfoil theory, and the far-field sound is computed using a compact body acoustic analogy. Results describe the impact of trailing edge elasticity on near- and far-field flow characteristics, and indicate on the amplifying effect of edge flexibility on the far-field sound. In particular, far-field radiation in the non-rigid case is affected by stronger edge-point airfoil interactions with incoming vorticity, as well as by long-time flow-induced oscillations at the system least stable eigenfrequency.