DSpace Repository

Welcome to the NLR Reports Repository

Royal NLR conducts research, which is published in reports. Only a minor part of these reports is made public. This repository holds these public, so called Technical Publications (TP), mainly produced from 1996 up till now.

Technical publications published before 1996 may be obtained using the request-form. Other types of NLR-reports are Contract Reports (CR) and Technical Reports (TR), which in general are not public. You may however request a copy by using the request-form. In some cases permission may be granted, depending on specific properties and contractor of the report. Reports will be supplied as pdf-file.

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Recent Submissions

Numerical interpretation of whirl flutter in a tiltrotor wind-tunnel model using mid-fidelity aerodynamics and mechanical friction
(Springer Nature, 2026) De Vita, P.; Cassoni, G.; Masarati, P.; Fonte, F.; Favale, M.; Hoff, S.C. van 't
This paper investigates the aeroelastic stability of the ATTILA tiltrotor wind-tunnel testbed through numerical modeling of the system’s advanced dynamic characteristics. Specifically, the study addresses discrepancies between baseline predictions and experimental observations regarding the unexpected sensitivity of flutter modes’ damping to rotor disk tilting. Two enhancements are explored: mid-fidelity aerodynamic modeling using vortex particle methods and mechanical friction modeling in critical joints. Vortex particle free wake and vortex lattice-based modeling for wing aerodynamics significantly improve damping predictions for the out-of-plane bending and torsion modes compared to strip theory approaches for the wing and rotor blades. In contrast, modeling rotor aerodynamics with lifting line and vortex particle free wake only shows marginal improvements. However, aerodynamic enhancements alone cannot reproduce the experimentally observed sensitivity to the gimbal angle. Conversely, introducing friction in specific joints can qualitatively replicate the observed tilt-dependent behavior through stiction-induced joint locking.
Sustainable, solvent-free exfoliation of 2D materials for thermally conductive metal powder coatings
(Nature, 2026) Koutsioukis, A.; Ruan, S.; Cabello, R.; Lee, H.; Oikonomou, I.M.; Guo, X.; Sasnauskas, A.; Munuera, J.M.; Rafferty, A.; Xiong, Y.; Dosta Parras, S.; Wits, W.W.; Yin, S.; Lupoi, R.; Nicolosi, V.
2D nanomaterials offer unique functional properties when combined with metal powder feedstock, enabling advanced composites for engineering and energy applications1. Scalable fabrication of nanosheet-reinforced metal matrix composites (2DMMCs) remains challenging. In this study, we first exfoliate 2D materials using a solvent-free ball milling approach, using graphene and hexagonal boron nitride (hBN) as demonstrators, and then attach the resulting 2D nanoplatelets onto a wide range of metal powders, including copper (Cu), titanium (Ti-6Al-4V), aluminum (AlSi10Mg), and stainless steel (SS316L). To provide a mechanistic understanding of exfoliation, we use density functional theory (DFT) and discrete element method (DEM) simulations, offering new insights into the forces that drive nanosheet exfoliation. The resulting 2DMMC powders combine excellent scalability and effectiveness. After consolidation, titanium alloy/graphene systems reaching thermal conductivity values of 17 W·m⁻¹·K⁻¹, comparable or superior to previous reports. Finally, we showcase their printability, confirming compatibility with large-scale manufacturing techniques and highlighting their potential for next-generation thermal applications.
Adaptive Automation and the Third Pilot
(IntechOpen, 2018) Cahill, J.; Callari, T.C.; Fortmann, F.; Suck, S.; Javaux, D.; Hasselberg, A.; Stroeve, S.H.
Currently, automation does not take into consideration the cognitive and emotional state of the crew. Rather, automation provides assistance based on explicit and static task assignments, with no adaptive capabilities, even though it is capable of providing higher or lower levels of support depending on the crew state and/or complexity of the operational situation. This chapter presents a new adaptive automation concept which offers an innovative ‘team’ centred approach to solving crew awareness/workload management problems and enhancing flight safety. Partnership underpins the ‘Third Pilot’ approach. The crew (pilot flying and pilot monitoring), automation and the ‘Third Pilot’ are in charge together. Overall, partnership is proposed. This replaces existing paradigms involving dynamic changes in control function, where changes can be autonomously controlled by the system. Moreover, a new multimodal cockpit concept is advanced providing enhanced assessment of crew state/workload.
Exploring the integration of live, virtual, and constructive environments in fighter pilot training through Link-16: lessons learned regarding training aspects
(Sage Journals, 2025) Thijssen, D.; Pelt, D.M.; Benthem, G.J. van; Zwaan, S.; Petermeijer, S.M.; Pal, J. van der
Live, Virtual, and Constructive (LVC) training has gained attention as a cost-effective and scalable approach to improve fighter pilot training. Despite its potential, achieving a highly interoperable LVC environment remains a challenge, limiting its widespread implementation in the near future. However, integrating existing technologies and operational datalinks offers opportunities to enhance training effectiveness, even with some limitations in interoperability and interaction. This study investigates the feasibility and benefits of incorporating LVC elements into training scenarios. In October 2023, a synthetic environment combining a virtual fighter and constructive elements was integrated into the large-scale Frisian Flag exercise. Through Link-16 datalink and ultra-high-frequency (UHF) radio connectivity, virtual and live elements exchanged data, allowing the virtual simulator to participate in Offensive and Defensive Counter Air missions alongside live pilots. Post-training evaluations indicated that the virtual and constructive elements positively impacted the training value for live pilots, while pilots operating the virtual simulator also reported benefits, albeit to a lesser extent than in live sorties. This paper focuses on the training outcomes within the context of Frisian Flag and seeks to provide broader insights for diverse training scenarios.
Unpacking the message: visual cues to reduce bystander uncertainty about delivery drones in public spaces
(Springer, 2026) Lingam, S.N.; Petermeijer, S.M.; Obaid, M.; Martens, M.H.
As drones are deployed in public spaces for tasks such as package delivery, drones will encounter the public as bystanders passing by. The distinctive character of bystanders is that they are not the package recipients, so they lack prior information about the drone. Clear communication of drone intentions is essential to reduce uncertainty and improve public safety and trust. Limited research, however, has examined how a drone’s communication strategies affect bystanders. This online questionnaire study investigated how a drone’s visual cues affect bystanders' uncertainty about a drone’s intentions. Participants (N = 150) viewed software simulated scenarios of drones delivering packages either by landing or by cable drop, each with or without visual interfaces (on-board lights, on-board display, or ground projection). Participants rated the scenarios for uncertainty, convincingness, predictability, understandability, and trust, and provided qualitative feedback through textual comments. Results illustrate that explicit communication improves bystanders’ ability to predict drone actions and influence bystanders’ intentions. While lights posed challenges with visual clarity, displays were effective for conveying drone movements, and projections were most preferred for indicating landing locations and safety zones. We recommend adapting interfaces, particularly ground projection, to provide instructions to bystanders on how to act (e.g., whether or not to cross) during drone operations. Our study contributes to the introduction of safe and trustworthy drones in public spaces.