Wall Integrated Pressure-Sensitive Paint Illumination for Improved Flow Quality in 16T

New technologies, such as Airborne Lasers, require high resolution aerodynamic measurements of loads and turbulence on conformal windows through which the energy is directed. This demand for global optical techniques and high definition flow visualization methods has driven the installation of more camera hardware and light sources in the test section walls of AEDC tunnels 4T and 16T. In the case of Pressure-Sensitive Paint, 40 LED illumination assemblies of ~ 4-inch diameter are currently distributed around the tunnel. Each light is composed of 21 high-power LEDs and this unit occupies an approximately 6-inch flanged window in the tunnel wall. The combined flanged window and LED unit blocks multiple porous holes in the walls. This has led to a reduction in the total wall porosity which is a critical component to the aerodynamic flow quality of a transonic wind tunnel. New walls that are compliant with this optical instrumentation are needed which embed light sources and possibly cameras within the walls in such a fashion that they do not interfere the distribution of porous holes. Here we propose replacing the current illumination assemblies with a system of individual LED pods of approximately 1.5-inch diameter that would be embedded into the tunnel walls. The pods would be positioned around the porous holes and eliminate the need for blocking porosity. The package will be designed around current LED power supplies and drivers to ensure compatibility with the existing PSP system. Each package will provide 6W of optical output at 395-nm, about 20% of the optical output of an existing LM4XX-400 unit. The small size of these pods, along with the fact that they fit between the wall porosity, allows significantly more illumination to be directed onto the model. Estimates of the number of pods that can be integrated into the wall suggest a 3X to 13X increase in model illumination can be achieved. This will result in higher signal-to-noise ratio data or shorter time on condition, which will improve tunnel productivity. The wall integrated pod will be designed to be removable for service and upgrades by simply unplugging the unit from the back and removing 4 screws. Finally, the package can be modified with other LED wavelengths or house small surveillance cameras for alternative measurements such as tunnel monitoring or model deformation measurements. The resulting system will improve facility flow quality, improve data quality, and improve tunnel productivity to support aerodynamic studies airborne directed energy weapons.