CAA Calculations of Vortex Trailing-Edge Interactions Using Nonlinear Disturbance Equations

Abstract

The interaction of vorticity with the trailing edge of airfoils is an important source of airframe noise. In order to study this process, in the present paper the interaction of a single vortex with the trailing edge of a generic airfoil of a modern transport aircraft under 6° angle of attack is calculated by the solution of two-dimensional nonlinear disturbance equations with a RANS mean flow in the Mach number range from 0.2 to 0.5. Non-linearities are taken into account up to first order. The emphasis of the present study rests on the assessment of the influence of the Mach number and non-linearities on the generated sound field. It has been found that the sound intensity downstream of the profile scales up to a mean flow mach number of 0.4 approximately like M*, which is near to the theoretical value. For M = 0.5 larger deviations exist most probably due to a broader mean vorticity profile in the wake. Taking into account non-linearities increases the sound pressure level in case of mathematically negative rotating initial vortices and decreases it in case of positive rotating ones although this effect is not so pronounced than in case of an infinite thin trailing edge.