In this wind tunnel testing application, German-Dutch Wind Tunnels chose Emergent 10GigE cameras with 20MP CMOS sensors because its optical fiber interface allowed them to run all four cameras from the wind tunnel simulation to a single remote PC.
German-Dutch Wind Tunnels (DNW) is one of the leading wind tunnel service providers in the world and was set up by the German Aerospace Center (DLR) and the Royal Netherlands Aerospace Centre (NLR). DNW operates six wind tunnels in Germany and the Netherlands, including in Brunswick, Göttingen, Amsterdam, and DNW’s headquarters in Marknesse. By placing aircraft, vehicle, building, or other solid models in an airstream of known velocity, wind tunnels allow researchers to investigate airflow around objects or the effect of wind on objects. DNW operates one of Europe’s largest wind tunnels and provides experimental simulation solutions for aerodynamic research and development projects from academia and the aeronautical industry, as well as from automotive, civil engineering, shipbuilding, sports, and other industries.
DNW provides experimental aerodynamic simulations. By running six wind tunnels, including subsonic, transonic, and supersonic facilities, DNW can evaluate almost all airflow characteristics found in engineering and nature. DNW supplies data to industry from aerodynamic, aero-acoustic, and aero-elastic simulation techniques by testing (scaled) models in a controlled environment. It offers a wide range of simulations. Typical applications include performance characterization of takeoff, landing, and cruising aircraft configurations; aero-acoustic investigations for airframe noise reduction; and simulation of aircraft propulsion in both isolated and installed configurations.
Wind tunnel tests are typically highly specialized and challenging (Figure 1). Wind tunnel models are complex and instruments are high tech. In addition to extremely tight manufacturing tolerances and meticulous surface finishing, models are equipped with a large amount of measurement equipment and control systems, such as force balances, air motors, and remote controls. In addition, aerodynamic and aero-acoustic simulations often require sophisticated engineering. For instance, for in-ground effect, the ground below the object under test is simulated with an integrated moving belt system. The moving belt, also known as a rolling road system, is a 7.92 x 9.6 m steel belt integrated into the wind tunnel floor. It moves synchronously with the air up to wind speeds of 80 meters per second. Integrating all simulation, control, and measurement technologies into a productive, cost-effective wind tunnel test is a daunting task. Highly trained DNW staff work closely with customers and suppliers to prepare projects in detail and to work toward innovative solutions for future sustainable aviation.
Figure 1: A model of a Dassault Falcon business jet in close proximity to the moving ground plane in the DNW-LLF wind tunnel (image courtesy of Dassault Aviation).
Stereoscopic Point Tracking System
A key capability for DNW is extracting as much high-quality data from a wind tunnel test as possible. To increase the quality and cost-effectiveness of its services, DNW is continuously developing high-level expertise in measurement techniques and analysis of test results. DNW routinely employs techniques for measuring surface pressures, forces, velocity, and noise. Evaluating aircraft performance involves a precise knowledge of exact propeller, rotor blade, and wing geometry. Under the various wind loads that occur from takeoff through landing, wind tunnel model parts deform, resulting in wing bending and twisting. A stereoscopic point tracking system developed by DNW measures such model deformation by simultaneously tracking markers from different angles during wind tunnel tests.
The system is flexible enough to facilitate a variety of experimental simulations, handling virtually any marker quantity, distribution, and layout. One current application is an EU-funded project called UHURA (funded under EU Horizon 2020 Grant Agreement no. 769088). The UHURA projects aims to develop numerical tools for unsteady high-lift aerodynamics. The Krueger flap, a leading-edge device, promises to enable laminar wing technology. This technology is seen as the major single source for drag reduction on the airframe of a transport aircraft and will be a key technology in achieving targets for emissions reduction. The Krueger flap could perform a dual function by both increasing aerodynamic high-lift performance and shielding the leading edge from contamination during takeoff and landing. Due to its specific deployment path, engineers need good knowledge of the flow during transient behavior and exact part position and geometry.
Experimental measurements from DNW wind tunnels give UHURA a unique dataset for validation of advanced computational fluid dynamics (CFD) models. With detailed flow measurements from particle image velocimetry (PIV) and model deformation measurements, interactions between the fluid and the wing structure can be investigated. The resulting understanding feeds into techniques for predicting behavior and design optimization of high-lift devices for transport aircraft systems. Such advanced methodologies enable more complex part designs and significant reductions in design lead times for aircraft manufacturers.