| Category | Description | |
|---|---|---|
| Responsible | Dr. Mariachiara Gallia | |
| Test Section Size | 0.5 m x 0.5m x 1.5 m | |
| Max. Velocity | 40 m/s | |
| Turbulence Level | max. 1.4% at 40 m/s | |
| Temperature | -20°C to 30°C | |
| Pressure | Ambient pressure - not controlled | |
| Supercooled Droplets App. C | MVD: 10µm to 60µm -- LWC: 0.1 g/m³ to 2.0 g/m³ | |
| Ice Crystals | MMD: ~ 80µm -- IWC: 3 g/m³ to 19 g/m³ | |
| Thermal output refrigeration system | 80 kW | |
| Electric drive | 30 kW |
The BIWT is a Göttingen type of wind tunnel, which is equipped for the investigation of multiphase flows and icing. In the modular, closed test section, tests on profiles, probes, but also vehicle parts can be carried out. The refrigeration system ensures constant temperatures down to -20°C. Two spray systems provide droplets with different diameters, with which investigations into droplet freezing are possible. A system for blowing in artificially generated ice crystals enables the investigation of ice crystal freezing on warm surfaces.
A highly productive cloud-chamber system was developed to grow and harvest realistic ice crystals. In each chamber, atomized water droplets are injected into a supersaturated cold airstream and frozen by rapid expansion of pressurized air; internal circulation suspends the crystals until they reach settling size and drop into a −70 °C chest freezer to prevent sintering. For wind-tunnel feeding, ice aggregates are volumetrically metered by a frequency-controlled dosing machine, then sieved (8 Hz oscillation) to isolate tens-of-micron particles. The sieved ice falls into a cooled, pressure-balanced conveyance pipe—airflow drawn from the tunnel and after-cooled—through a calibrated injector nozzle. After about 30 s this produces a stable mass flow of particles, which are injected as a 20 m s⁻¹ jet into the tunnel’s settling chamber and mixed with the main airflow.
Our research integrates fundamental laboratory studies with application-oriented icing–wind-tunnel experiments with main focus on in-flight icing. In the wind tunnel, we perform controlled ice-accretion tests with both supercooled droplets and ice-crystals to understand the physics of ice inception, layer growth, melting and eventually shedding, and to evaluate thermal anti-icing systems, mechanical de-icing boots and passive coatings under realistic airflow and temperature conditions. To capture the complex dynamics of icing, we deploy and develop measurement techniques—high-speed imaging and laser-based sensors to map droplet-cloud trajectories and size distributions (see the Interferometric Particle Imaging example in the middle figure), photogrammetric and optical techniques for detailed ice-shape reconstruction (top figure), and high-resolution cameras to resolve fine microstructures and dynamic impact events such as an ice crystal striking a surface and fragmenting (bottom figure).