Final work : Pressure Field Reconstruction and Calibration Plate for Inlet Distortion Stereo-Particle Image Velocimetry

Abstract

Aircraft engine intakes have presented design and propulsive challenges since modern civil and military vehicles took flight. Be it for complex upstream geometries and flow paths or for flight envelope manoeuvres during taxi, take-off climb or cruise, one of the most important remains inlet distortion, and as such, it requires accurate flow characterisation.

Inlet distortion comes in the form of swirling and/or pressure patterns, thus the need of both reliable 3D time-resolved velocity and pressure information. Although with downsides, Stereoscopic Particle Image Velocimetry has proven reliable in providing time-resolved velocity datasets of high spatial resolution. Pressure from PIV presents an alternative to intrusive rake probes for such data acquisitions in spite of its complexity, cost, an uncertainty quantification.

In this context, the current project aims to design a low speed wind tunnel experiment for inlet distortion SPIV and the development of a post-processing tool to retrieve pressure from PIV. The distortion is achieved by means of pressure and swirl devices that create different flow patterns to be temporally investigated. Laser sheet optics were tested, proper focus on the desired field of view was demonstrated with Scheimpflug adaptors, and a 3D calibration plate was devised.

Steady space marching integration and poisson methods were developed and compared to retrieve the pressure field from three interpolated 'synthetic' CFD case studies. In light of the apparent flow characteristics disparity between the three case studies, the incompressibility assumption was evaluated just as the computation of axial gradients.

Space marching performed below poisson for most cases and assumptions. Incompressible assumption captured surprisingly accurately pressure gradients and distortion under Mach number conditions that would not be considered incompressible. Axial gradients had a mostly non-positive effect: computing them saw irrelevant positive effect on accuracy or significantly added up to computation error.