Numerical and experimental studies on high-speed stall phenomena

Abstract

This special issue summarizes research findings on high-speed stall phenomena with a focus on transport aircraft obtained during the first phase of the research initiative jointly funded by the German Research Foundation (DFG) within the research unit FOR 2895 “Unsteady flow and interaction phenomena at High-Speed Stall conditions” and the Helmholtz Association of German Research Centres (HGF). All papers have been peer reviewed according to the standards of the CEAS Aeronautical Journal. The aerodynamics of transport aircraft at the borders of the flight envelope is characterized by complex interactions and nonlinear, unsteady flow phenomena. The overall goal of the research initiative introduced above is the detailed numerical and experimental investigation of the flow-physical mechanisms and phenomena for these conditions up to flight-relevant Reynolds numbers. A prominent feature of the initiative are extensive measurements in the cryogenic European Transonic Windtunnel (ETW) on the Airbus XRF-1 aircraft research configuration. In addition to polar measurements, static pressure distributions are measured by numerous pressure taps, while unsteady pressures are recorded by Kulite sensors in relevant areas of the XRF-1 wing, horizontal tail plane (HTP), and ultra-high bypass ratio (UHBR) flow-through nacelle. To provide a comprehensive characterization of the flow, sophisticated optical methods are applied to measure the unsteady surface pressure distribution by the unsteady pressure-sensitive paint (PSP) technique and the flow field by means of unsteady particle image velocimetry (PIV). One goal of the research initiative is to provide a comprehensive, high-quality experimental database for future scientific use, both within and outside the present research initiative.