Numerical Investigation of Passive Flow Controls in Subsonic jet Flow and Noise

Abstract

Passive flow control devices on jet nozzles, such as chevrons, have been largely applied on modern turbofan engines aiming the decrease of the noise by increasing flow mixing. In this sense, several numerical and experimental investigations have been conducted to better understand the phenomenon of noise reduction through the application of such passive devices. The present paper reports a numerical study of jet flow operating at Mach number 0.9 and Reynolds number 1.38x10 6 . Three nozzle geometries are used for the simulations: a baseline nozzle without any chevron and two different chevron nozzles that differ from each other by their penetration angle into the flow. The aim of the study is to verify the capability of two hybrid approaches in predicting the effects of the chevron geometry on the SPL spectrum at the far field. RANS simulations were conducted using both a cubic k-ε model and a Reynolds Stress Transport model, whereas the acoustic field was calculated using the Lighthill Ray Tracing (LRT) method and the waveprop1 method available in the commercial code CAA++ from Metacomp Tech. The results obtained with the LRT method show a satisfactory agreement with experimental data, suggesting it can be used to investigate noise spectra at the far field of chevron nozzle jet flow at a reduced computational cost. Nomenclature! = sound velocity outside the jet ! ! = normalized vector ! = nozzle diameter = mass-averaged turbulent kinetic energy = local pressure ! = turbulent kinetic energy production term !" * = strain rate tensor !" = Lighthill's stress tensor ! " ! " = mass-averaged Reynolds stress ! = flow velocity !"= Kronecker delta = mass-averaged viscous dissipation = averaged density = dynamic viscosity ! = turbulent viscosity Ω !" = mean vorticity tensor 1 M.Sc Researcher, engel@polo.ufsc.br 2 Full Professor, deschamps@polo.ufsc.br 2 Full Professor, deschamps@polo.ufsc.br 3 Technology Development Engineer, carlos.ilario@embraer.com.br Downloaded by CORNELL UNIVERSITY on July 30, 2015 | http://arc.aiaa.org |