Normal Shock Wave-Turbulent Boundary Layer Interactions in Transonic Intakes at Incidence

Abstract

The flow field around a transonic engine inlet lip at high incidence is investigated for a variety of flow conditions around the design point. Generally, the flow on the upper surface of the lip is characterised by a supersonic region, terminated by a near-normal shock wave. At the nominal design point, the shock is not strong enough to cause significant flow separation, resulting only in marginal losses in pressure recovery. Off-design conditions were explored by altering the angle of attack as well as changing the mass flow rate over the upper lip, intended to mimic the effect of an increase in engine flow. The results suggest that angle of attack has the greatest effect on the flow field. In particular, even a relatively small increase of 2 • can lead to large and highly unsteady flow separation with an associated shock oscillation. Both qualitative and quantitative measurements suggest a noticeably reduced aerodynamic performance resulting from higher incidence operation. In contrast, an increase of up to 5.2% in mass flow over the upper part of the intake lip did not result in large separated regions or flow-field unsteadiness.

Effect of Lip Shape on Shock Wave-Boundary Layer Interactions in Transonic Intakes at Incidence

“…This is similar to the baseline incidence. The estimated mean separation size, which was found [5] to be correlated to the distance between the shock and the isentropic sonic line in Figure 9, is expected to have grown in size as there is an increasingly greater smearing of the pressure rise. Furthermore, a more extensive region of smeared pressure near the corners is observed at higher incidence.…”

“…This paper aims to identify the main factor affecting the boundary layer development downstream of a normal shock wave -boundary layer interaction. Four inlet lip variations are considered here, along with a representative inlet shape (based on a current inlet geometry and amply discussed in a previous paper [5]).…”

“…This is generally found in the presence of a weak centre-span interaction resulting in small or absent separation. From Figure 9, using the smearing of the pressure rise between the onset and the isentropic sonic line as an indication for the size of separation [5], it seems likely that a recirculating region is present for each lip; this is expected to be larger for the thick lip.…”

Numerical Modelling of Shock Wave Boundary Layer Interactions in Aero-Engine Intakes at Incidence

“…The rig is designed with the aim of finding a simple geometric configuration that replicates the key physics found in a real intake at incidence, allowing study of such phenomena and providing experimental validation data sought for by computational models. The intake rig was designed and built by fellow PhD student Tafara Makuni [15,21] and experimental measurements used in this work were made by fellow PhD student Andrea Coschignano [23,24], both under the supervision of Professor Holger Babinsky at the Department of Engineering, University of Cambridge. The motivation for this study and the experimental effort is driven by a lack of previous research both experimentally and computationally that investigates transonic high incidence lip flows found in intakes at incidence (as found in the literature review).…”