Schematic of the VKI H-3 blowdown hypersonic tunnel equipped with interchangeable contoured nozzles enabling Mach 5 and Mach 6 operation
The VKI H-3 wind tunnel stands out as one of the few European hypersonic facilities enabling aerodynamic and aerothermal characterization of launchers, cruise vehicles, re-entry vehicles and space-debris.
Equipped with interchangeable axisymmetric contoured nozzles, the VKI H-3 blowdown wind tunnel produces exceptionally uniform (>99.7%) Mach 5 and Mach 6 free jets with core flow diameters exceeding 120 mm. The facility utilizes dry air supplied from a pebble-bed heater, capable of delivering stagnation pressures between 5 and 35 bar and achieving a maximum stagnation temperature of 550 K. This setup allows for a versatile range of free-stream unit Reynolds numbers, spanning from 3x10^6 to 35x10^6 per meter, within a finely characterized environment.
The test section is equipped with a high-accuracy five-degree-of freedom orientation mechanism and a rapid injection mechanism that enables model injection into the hypersonic stream in less than 0.1s. An efficient supersonic ejector further enhances the facility's capabilities, enabling extended test durations exceeding 30 seconds and supporting a high frequency of daily test runs.
Modern data acquisition is handled by a sophisticated National Instrument system, which supports a variety of instrumentation techniques. These include localized measurements using thermocouples and pressure sensors, as well as global measurement techniques such as oil flow, sublimation, Infra-Red thermography, and Temperature-Sensitive Paint (TSP). Aerodynamic data are typically gathered using three-component aerodynamic strain gauge balances. The tunnel also boasts high-quality shadowgraph and schlieren optical systems, along with advanced optical and non-intrusive measurement techniques like Laser-Induced Fluorescence (LIF), Planar Laser-Induced Fluorescence (PLIF), and Interferometric Laser Imaging for Droplet Sizing (ILIDS) for specialized requirements.
The main scientific contributions include the generation of comprehensive aerodynamic and aerothermal databases, validation of numerical simulation tools, and fundamental research into critical hypersonic phenomena such as natural and roughness-induced boundary layer laminar-to-turbulent transition, shock wave boundary layer interactions, liquid fragmentation in crossflow, and ablation processes...
Schlieren flow visualization in the VKI H-3 tunnel
Pressure rake used for the VKI H-3 nozzle flow uniformity characterization