Lights, Camera, Data: Optical Technique Development at ARA

The Transonic Wind Tunnel (TWT) of the Aircraft Research Association (ARA) has been an invaluable resource for aircraft manufacturers since 1956. However, with the ever-increasing demand for further efficiency and performance, in both civil and military programs, standard testing techniques such as forces & moments from internal balances and pressure taps alone cannot offer the insight required into the complex flow phenomena and aircraft behaviour at off-design conditions. This is driving interest in the use of advanced optical diagnostics techniques to capture both on-surface and off-body data over wide areas with minimal intrusion, such as pressure-sensitive paint (PSP), infrared thermography (IRT), particle image velocimetry (PIV) and model deformation measurements (MDM). These methods have been developed and come to fruition over many years in laboratory settings and have been invaluable for new understandings of flow physics in small tunnels. Deploying them in the harsh environments of an industrial wind tunnel and ensuring they are robust enough for commercial operation bring an additional array of challenges that ARA has been working hard to solve.