Development of open-loop supersonic jet rig facilities

In this work, we present the design and commissioning of two laboratory‑scale rigs that generate well‑regulated free and impinging underexpanded supersonic jets. The large-scale rig consists of a pair of high-capacity compressors (175 psi, 1000 CFM), two air driers, and two storage tanks (400 cubic feet each). Flow passes through a pair of automated pneumatic valves, and a flow conditioning tank before exiting a convergent nozzle with an exit diameter of 3 inches. Nozzle pressure ratio (NPR) is maintained by a real‑time feedback loop from the valve's downstream pressure transducer. The small-scale rig draws air from the laboratory compressed-air line at 100 psi. The nozzle pressure ratio is precisely regulated using a pressure air filter/regulator, and a mass flow meter. A flow conditioning vessel packed with honeycomb and wire‑mesh inserts leads to a modular mount fitted with a 0.2-inch convergent nozzle. Both rigs include injection ports for smoke tracers and inertial particles, enabling PIV for unladen jets and PTV for particle‑laden flow measurements in the future. High‑speed schlieren imaging captures shock‑cell structure and startup transients over a broad operating envelope. We present the development process from steady and transient RANS simulations to preliminary experimental validation, with a focus on bridging the gap between high-fidelity simulations and measured data with particular emphasis on drag coefficient estimation.