The unsteady flowfields generated by convoluted aeroengine intakes are sources of instabilities that can compromise the performance of the downstream turbomachinery. Hence, there is a need for synchronous high-spatial-resolution measurements that will allow a greater understanding of the aerodynamics. In this work, stereo particle image velocimetry is used in a new application to characterize the distorted flow at the outlet of complex intakes. A suite of measurements and analyses for two S-duct configurations across a range of inlet Mach numbers is presented. The work demonstrates the feasibility of using stereo particle image velocimetry techniques for determining the flowfield at the exit of convoluted intakes with a higher spatial resolution than typical pressure measurements. Analysis of the distortion descriptors quantifies the dependency upon the S-duct configuration and highlights that the more high-offset duct generates greater levels of swirl distortion relative to the low-offset configuration. Distortion maps show that the flow is highly unsteady with a characteristic switching of the swirling flow. The results provide a new dataset that shows that the conventional assessments based on time-averaged data substantially underestimate the swirl distortion level and that the less frequent distortion events give rise to more potentially significant threats to the compression system.

For many embedded engine systems, the intake duct geometry introduces flow distortion and unsteadiness, which must be understood when designing the turbomachinery components. The aim of this work is to investigate the capabilities of modern computational methods for these types of complex flows, to study the unsteady characteristics of the flowfield, and to explore the use of proper orthogonal decomposition methods to understand the nature of the unsteady flow distortion. The unsteady flows for a range of S-duct configurations have been simulated using a delayed detached-eddy simulation method. Analysis of the conventional distortion criteria highlights the main sensitivities to the S-duct configuration and quantifies the unsteady range of these parameters. The unsteady flowfield shows signature regions of unsteadiness, which are postulated to be related to the classical secondary flows as well as to the streamwise flow separation. A proper orthogonal decomposition of the total pressure field at the duct exit identifies the underpinning flow modes, which are associated with the overall total pressure unsteadiness distributions. Overall, the unsteady distortion metrics are not found to be solely linked to a particular proper orthogonal decomposition mode, but are dependent on a wider range of modes.

A tool to create parametric aerodynamic shapes using intuitive design variables based on class shape transformation (CST) curves is presented. To enable this, a system has been developed which accepts arbitrary constraints and automatically derives the analytical expressions which describe the corresponding class shape transformation curves. Parametric geometry definitions for fan cowl and intake aero-lines were developed using the generalized method. Computational fluid dynamics (CFD) analysis of the fan cowl shows that despite the simple geometry definition, its performance characteristics are close to what would be expected of a finished design. The intake geometry was generated in a similar way and met the typical performance metrics for conventional intakes. This demonstrates the usefulness of the tool to quickly and robustly produce parametric aero-lines with good aerodynamic properties, using relatively simple intuitive design variables.