Unsteady inlet flow distortion can influence the stability and performance of any propulsion system, in particular for more novel, short and slim intakes of future aero-engine configurations. As such, the requirement for measurement methods able to provide high spatial resolution data is important to aid the understanding of these flow fields. This work presents flow field characterisations at a crossflow plane within a short aeroengine intake using stereoscopic particle image velocimetry (SPIV). A series of tests were conducted across a range of crosswind and high angle of attack conditions for a representative short and slim aspirated intake configuration at two operating points in terms of mass flow rate. The velocity maps were measured at a crossflow plane within the intake at an axial position L/D = 0.058 from where a fan is expected to be installed. The diameter of the measurement plane was 250 mm, and the final spatial resolution of the velocity fields had a vector pitch of 1.5 mm which is at least two orders of magnitude richer than conventional pressure-based distortion measurements. The work demonstrates the ability to perform robust non-intrusive flow measurements within modern intake systems in an industrial wind tunnel environment across a wide range of operating conditions; hence, it is suggested that SPIV can potentially become part of standard industrial testing. The results provide rich datasets that can notably improve our understanding of unsteady distortions and influence the design of novel, closely coupled engine-intake systems.

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Volumetric particle tracking velocimetry measurements are performed in a low-speed wind tunnel to study the flow around a 1:12-scale aircraft model with jet engines operating with thrust reversers. The engine jet and freestream flow velocity are varied to yield a jet to freestream velocity ratio of V_jet/V_∞ ranging from 1.5 to 6. Measurements at such scale (0.5 m³) require the use of strongly scattering helium-filled soap bubbles as flow tracers, which are introduced in both the jet and the freestream flow. The tracer’s three-dimensional motion is determined using an array of cameras and a Lagrangian particle tracking algorithm. The mean velocity field reveals the jet inner structure as well as its interaction with the freestream, the ground board, the nacelle, the fuselage, and the horizontal and vertical tails. The experiments allow detection of exhaust reingestion as well as the aerodynamic interference with control surfaces at the tail segments in a single measurement volume. The results are in good agreement with conventional temperature rake measurements while adding details of the flow topology and of the large-scale unsteady flow fluctuations. Finally, the jet reversal characteristics with varying freestreams and nozzle pressure ratios are assessed, demonstrating the feasibility and versatility of volumetric velocimetry measurements for industrial aerodynamics.

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Volumetric PIV measurements are performed to study the flow development around a 1:12 scale model of a thrust reverser in a low-speed wind tunnel. The thrust-reverser operates in a freestream flow of 3-5 m/s and with a jet to freestream velocity ratio Vjet/Vinf ranging from 1.5 to 6. Making use of sub-millimeter helium-filled soap bubbles, large-scale PIV measurements are performed that encompass a 3D domain of approximately 0.4 m3. The flow exiting the thrust-reverser features two inclined jets that interact with the wind tunnel free stream, the nacelle, fuselage and ultimately the tunnel walls. Such interactions result in highly three-dimensional patterns and jets large scale fluctuations. The jet reversal characteristics with varying freestream velocity and nozzle pressure ratio are characterized quantitatively. The work demonstrates the feasibility of quantitative inspection of the flow behavior in a three dimensional domain for industrial applications.@en