Other publications
Permanent URI for this collection
Other than NLR reports
Browse
Recent Submissions
1 - 5 of 110
-
ItemRadiated emissions from power feeders for electric propulsion in aircraft(IEEE, 2022)Electric propulsion is a major focal point for aviation industry towards achievement of international sustainability goals. These developments will cause an inevitable increase in on-board power levels, implying higher voltages and currents. One of the various corresponding challenges in electromagnetic compatibility concerns the radiated emissions of power feeders. This paper focusses on the modelling of these emissions from three-phase power feeders by a combination of multiconductor transmission line modelling for determination of the currents in power feeders, and the Hertzian Dipole method to determine the radiated electric fields. Simulations and measurements are performed on the case of a single wire above ground, as well as a three-phase power feeder, resulting in a good match between theory and practice. The obtained simulation methods can also be used in combination with actual currents flowing onto the cabling, obtained either from measurements or simulations, to estimate the total in situ radiated emissions from three-phase power feeders.
-
ItemComparison of Classical and Optimization-Based Motion Cueing for Simulating Aircraft Upset Maneuvers(AIAA, 2025)Providing adequate simulator motion cues for simulated upset and stall scenarios remains challenging. This paper evaluates the potential of novel optimization-based motion cueing algorithms for upset and stall simulation. An offline analysis is performed to compare three Model Predictive Control (MPC) algorithms with varying prediction horizon lengths and prediction strategies (i.e., "Oracle", "Perfect", and "Constant") against two baseline classical washout algorithm implementations from literature. The analysis is performed for a symmetric stall scenario flown with TU Delft's Cessna Citation II laboratory aircraft. Overall, the analysis shows that the objective motion cueing quality expressed in terms of the Root Mean Square Error (RMSE) improves by 29.8% (for specific forces) and 18.7% (for rotational velocities) with the "Oracle" and "Perfect" MPC implementations compared to the reference classical washout results. For the "Constant" MPC algorithm, which in fact does not include any explicit prediction across the MPC algorithm's future prediction window, only a marginal improvement in motion quality was found. Overall, these results imply that, assuming a sufficient future reference motion prediction can be achieved, optimization-based motion cueing algorithms have the potential to provide significantly better motion cueing quality compared to classical motion cueing algorithms.
-
ItemTDOA based ADS-B validation using a Particle Filter and Statistical Hypothesis testing(IEEE, 2024)ADS-B is a widely used protocol that transmits aircraft’s position, velocity among other data. The protocol is not encrypted leading to the need of validation. A validation algorithm is proposed that makes use of Time Difference of Arrival localization to validate the position and velocity of ADS-B transmitting targets. Nowadays, Air navigation service providers (ANSP) commonly have at least one TDOA localization system in operation, allowing for cost effective implementation. Validation is achieved by using a Particle Filter and hypothesis tests. A novel method is used where the initial density is generated effectively based on the first set of TDOA measurements. Validation is possible when two or more ground stations receive the same ADS-B transmission, therefore the Particle Filter is designed to process such measurements. The algorithm is tested on data provided by Air Traffic Control The Netherlands’ North sea surveillance system. Results show that the validation works and that the algorithm is able to detect spoofing. Based on spoofed ADS-B messages and true TDOA measurements, the real and fake target can be detected when the distance is roughly 750 to 1000 meters (depending on the situation and the various tuning parameters). In addition, validation based on two or more ground stations per measurements has the effect that the validation area is increased, when compared to traditional filters that require 4 ground stations for tracking.
-
ItemUnsteady Adjoint Method for Aeroacoustic Propeller Optimization(AIAA, 2021)The development of an adjoint method for design optimization of a propeller in an unsteady flow field is presented. The methodology follows the continuous-discrete approach, where the adjoint equations are formulated in a continuous form and afterwards discretized in the same way as the flow equations are discretized. The time-dependent flow and adjoint equations are solved respectively to determine the aeroacoustics performance and gradients of the functionals. The aerodynamic characteristics are obtained using NLR’s CFD solver ENSOLV, while the acoustic characteristics are calculated using the Ffowcs Williams and Hawkings equation. Two aspects are highlighted, namely the development and verification of (i) the unsteady adjoint solver and (ii) the adjoint phase-lagged boundary condition. Computational results are presented for test cases ranging from an academic single airfoil to an industrially relevant propeller configuration.
-
ItemAcoustic Lucky Imaging for microphone phased arrays(Elsevier, 2023)Acoustic imaging methods are used to detect and quantify aerodynamic noise sources in aeroacoustic experiments. In wind tunnels with an open jet test section the sound wave propagating from an aeroacoustic source to a microphone array is distorted by the shear layer in the propagation path. The velocity fluctuations caused by the turbulence in the shear layer continuously alter the propagation time between source and observer causing reduction of the coherence between two microphone signals. The reduction in coherence is stochastic and dependents on the relative position between source and microphone. This leads to blurred acoustic source images with reduced peak Sound Pressure Level. This paper presents the Acoustic Lucky Imaging methodology, based on a methodology in astronomy to correct for image distortion due to turbulence present in Earth’s atmosphere. Furthermore, a model for coherence loss is derived to explain the loss of acoustic image resolution and allow for a-priori estimates on acoustic image blurring. The methodology is applied to an acoustic data set obtained in the open jet of a large industrial wind tunnel. It is shown that the presented methodology can restore a loss of 6 dB peak Sound Pressure Level by 3 dB and increase the resolution of the acoustic image at 8 kHz, a wind tunnel speed of 34 m s−1, and a shear layer thickness of ~1 m.