A Crucial Milestone for Open Fan Validation at DNW, Braunschweig

In mid-March 2025, the PANDORA consortium gathered in Braunschweig, Germany, for its mid-term review meeting—an essential milestone in the progress of this pioneering European research project. Hosted by DNW-NWB (German-Dutch Wind Tunnels), one of the most prestigious and capable aerodynamics testing institutions in Europe, the meeting provided the perfect setting to assess progress, align objectives for the second half of the project, and visit one of the few wind tunnel facilities in Europe capable of hosting the ambitious PANDORA open fan tests.

The event was held on-site at the DNW-NWB low-speed wind tunnel, in its open configuration—a state-of-the-art facility that plays a vital role in PANDORA’s mission to validate the performance and environmental viability of open fan propulsion systems. The meeting combined high-level technical discussions, strategic alignment, and an up-close look at the very infrastructure that will enable key experimental phases of the project.

With its large test section, modular architecture, and ability to switch between closed and open configurations, the DNW-NWB tunnel is uniquely equipped to support complex propulsion and aerodynamics experiments.

The open test section of the wind tunnel was of particular interest to the PANDORA team, as it offers controlled conditions ideal for gathering high-fidelity data. This is critical for validating the aerodynamic and acoustic performance of open rotor engines, which operate differently from conventional turbofans. Open rotors lack nacelles and use counter-rotating propellers to achieve high propulsive efficiency, especially in cruise phases of flight.

During the visit, consortium members had the opportunity to tour the DNW-NWB wind tunnel in person, receiving presentations from DNW’s engineers on its capabilities, historical significance, and preparations for upcoming PANDORA-related test campaigns. Seeing the test section and the measurement systems up close added a tangible dimension to the otherwise conceptual work many of the participants deal with on a daily basis.

The mid-term review also marked the halfway point in PANDORA’s timeline, offering a natural opportunity to evaluate the progress achieved so far, assess any risks or technical bottlenecks, and refine the action plan for the months ahead. Participants included representatives from all project partners, along with members of the advisory board and European Commission observers.

Among the various facilities across Europe, only a select few are capable of hosting the complex and specialized tests required by the PANDORA project. The DNW-NWB low-speed wind tunnel in Braunschweig—operated by the German-Dutch Wind Tunnels (DNW)—is one of those rare and strategically important locations.

What makes this tunnel particularly valuable for PANDORA is its ability to operate in an open configuration, a feature that enables unique experimental setups critical to the project’s goals. In this open configuration, one side of the tunnel is physically opened to allow the installation of an anechoic chamber—a specialized space designed to absorb sound waves and eliminate reflections. This setup is essential for carrying out precise acoustic measurements.

Thanks to this open layout, engineers can deploy advanced microphone arrays around the test section to capture the noise signature of the open fan system from multiple angles and distances. These measurements are vital for understanding how noise is generated, propagates, and can be mitigated—especially since open fan propulsion systems, while more fuel-efficient, can produce different and potentially louder noise patterns compared to traditional turbofan engines.

This unique capability to integrate aeroacoustic testing into a full-scale wind tunnel environment makes DNW-NWB a cornerstone of PANDORA’s experimental strategy. The data gathered here will help validate simulation models, support regulatory compliance, and guide future design improvements in low-emission propulsion systems.

In addition to this critical acoustic functionality, the DNW-NWB tunnel offers a large test section, adaptable infrastructure, and a legacy of successful testing in European aerospace projects—making it a proven and trusted asset for the ambitious goals of PANDORA.

As with any ambitious research project, the people involved are just as important as the tools and technologies. The mid-term review meeting in Braunschweig allowed members of the consortium to reconnect face-to-face, fostering the kind of informal conversations and brainstorming that often spark new ideas or help resolve persistent challenges.

By visiting DNW in person, participants were able to see the future stage of their experimental campaign and strengthen the partnerships that drive the project forward. These in-person meetings serve as reminders of the collaborative spirit underpinning European innovation efforts—especially in fields as interdisciplinary and impactful as sustainable aviation.