SWiFT2: Steady and Unsteady PSP Measurements on the SWiFT Model in the European Transonic Windtunnel

This paper presents recent Pressure-Sensitive Paint (PSP) measurements on the SWiFT (“Swept Wing Flow Test”) configuration, a blended/hybrid wing body model developed within the NATO AVT-298 research task group. The SWiFT model was specifically designed to reproduce the flow physics relevant to full-scale blended-wing-body aircraft, for which Reynolds number effects represent a key development challenge, particularly in high-lift conditions. Since industry-standard low-Reynolds number facilities and current computational methods do not reliably capture these effects, the AVT-298 group established the SWiFT configuration as a dedicated research platform for coordinated numerical and experimental investigations. In the present study, PSP measurements were carried out in the European Transonic Windtunnel (ETW) under cryogenic conditions at Reynolds numbers up to 48 million. Several measurement approaches were applied. First, steady-state PSP data were obtained using a lifetime-based multigate CCD system. Subsequently, time-resolved PSP measurements employing the intensity method with high-speed CMOS cameras (at 1 kHz) were performed to analyze unsteady flow phenomena such as flow separation and buffeting. Finally, continuous PSP measurements using CMOS cameras at 125 Hz were acquired during a slow angle-of-attack sweep (Δα = 0.12°/s). The results highlight the capability of PSP to resolve both steady and unsteady surface pressure distributions on the SWiFT configuration at flight-relevant Reynolds numbers. The time-resolved PSP data reveal a clear Reynolds number dependency at the onset and the amplitude of buffeting, demonstrating the suitability of PSP in supporting the objectives of the AVT-298 research task group.