Installation Effects Characterization of VHBPR engine PART II: Experimental study using Particle Image Velocimetry

This paper is the 2nd part of a series of four papers presenting the characterization of installation effects for typical high bypass ratio engine using both experimental investigation and numerical simulations conducted in the framework of the European research projet VITAL. The final objectives are a better understanding of the link between jet flows and generated noise, the validation of methods for computing the aerodynamic field and noise sources for industrial configurations, and the assessment of the benefits of a serrated nozzle when installed under a wing profile. This paper is dedicated to the aerodynamic measurements performed by 3-component Particle Image Velocimetry (stereo-PIV). Both longitudinal and cross stream PIV were implemented and allowed to explore the jet development up to 13 fan diameters in the symmetry plane as well as to catch its azimuthal structure at different axial positions. The influence of the pylon is exhibited. It strongly modified the azimuthal jet structure and increased the turbulence level in the upper shear layer. The comparison of both nozzles demonstrated unexpected results: the serrated nozzle induced a strong decrease of the turbulent kinetic energy (TKE) up to about 10 fan diameters and slight higher TKE farther downstream. The potential core length is increased and the mixing layers are thinner which is not in line with classical jet mixing devices. An objective of this part of VITAL is to study the low-noise nozzle efficiency under wing installation. The PIV measurements showed that the effect of the installation under a 2D high lift wing (EUROPIV model) is similar for both nozzles.