Computational and Experimental Flowfield Analyses of Separate Flow Chevron Nozzles and Pylon Interaction

Abstract

A computational and experimental flow field analyses of separate flow chevron nozzles is presented. The goal of this study is to identify important flow physics and modeling issues required to provide highly accurate flow field data which will later serve as input to the Jet3D acoustic prediction code. Four configurations are considered: a baseline round nozzle with and without a pylon, and a chevron core nozzle with and without a pylon. The flow is simulated by solving the asymptotically steady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, up-wind, flux-difference splitting finite volume scheme and standard two-equation k − ε turbulence model with a linear stress representation and the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. The current CFD results are seen to be in excellent agreement with Jet Noise Lab data and show great improvement over previous computations which did not compensate for enhanced mixing due to high temperature gradients.

Jet-Pylon Interaction of High Bypass Ratio Separate Flow Nozzle Configurations

“…al. 5 ) and the acoustic effects reported here. The models corresponded to an approximate full scale to model scale factor of nine.…”

Turbulent Flow Field Measurements of Separate Flow Round and Chevron Nozzles with Pylon Interaction Using Particle Image Velocimetry

“…An initial Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) study reported by Thomas et al 1 predicted mean and turbulent flow fields for various separate flow nozzle configurations including the pylon and core chevron nozzle. More recently, Massey et al 2 improved the computations by accounting for increased mixing due to high temperature gradients and showed excellent agreement with mean flow field measurements. These results have been used by Hunter et al 3 to predict the jet noise associated with these nozzle configurations using a 3-D noise prediction code called Jet3D.…”

“…A comparison of the mean axial velocity for the PIV measurements and rake measurements taken in the same facility 2 18 months prior to the PIV test is shown in Figure 7. Four different axial locations are shown.…”

“…As these various tools evolve in the PAA program, it is important to evaluate how the CFD compares to the current experimental results. The CFD results are from Massey et al 2 using a three-dimensional Reynolds-averaged Navier-Stokes solver (PAB3D) which employs a standard two-equation k-e turbulence model with a linear algebraic Reynolds stress representation. Furthermore, a correction is applied to the eddy viscosity model that is based on total temperature gradient in order to predict more accurate levels of mixing for high temperature jets.…”

High Bypass Ratio Jet Noise Reduction and Installation Effects Including Shielding Effectiveness

“…NASA and industry had already developed considerable experience that gave NASA the confidence that this key assumption could be realized. This understanding had been developed through a series of extensive experimental and computational studies beginning in 2002 through 2005 on the fundamental effects of jet noise reduction and jet noise source re-distribution with chevron and pylon effects [3][4][5][6][7][8][9][10][11] . Building on this information by 2009, ERA had already developed a technical path for an HWB concept to reach the noise goal.…”