M. Radaelli
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High-speed Unmanned General-purpose Observatory (HUGO)
Reusable test platform for high-speed aeroelastic research
Bachelor thesis
(2026)
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A. Arends Martinez, V. Byreddy, G. Castro Lima da Silva, T. Čokonaj, P. Dimitrova, A. Gheorghiu, M. Gryszka, A. Janeček, H.M. Skrobanek, C.G.M. Vistisen, S. Giovani Pereira Castro, J. Iori, M. Radaelli
This report details the design, engineering, and commercial feasibility of the High-speed Unmanned General-purpose Observatory (HUGO), a 50 kg modular transonic flying laboratory. HUGO aims to address the gap between scale wind-tunnel testing and full-scale flight validation. Operating primarily at Mach 0.75, HUGO bypasses the wall-interference limitations of conventional transonic wind tunnels and the severe safety risks associated with manned flight testing. To meet its experimental objectives, the finalized airframe features a high-wing, T-tail configuration with a modular wing, canard and empennage ports and retractable steel landing gear. A defining feature of the platform is its customizable "Planform Envelope," which allows clients to interchange main wing configurations with aspect ratios ranging from 5 to 27, as well as various sweeps, chords and thickness profiles. To cost-effectively produce in low volumes, while maximizing structural efficiency, the airframe utilizes a composite monocoque structure capable of safely withstanding ultimate load factors of up to 9g. Propulsion is provided by twin fuselage-mounted JetCat P100-RX-BL micro-turbines, enabling HUGO to execute a 30-minute nominal mission that includes a five-minute Mach 0.75 test segment at FL270. Because high-fidelity data collection is the core value proposition of a flying laboratory, the aircraft is equipped with a comprehensive payload suite, including dual LIDAR wing deflection sensors, 16 surface-mounted strain gauges, and 6-axis load cells, to isolate and measure aerodynamic forces. Commercially, HUGO targets a €14.2 million Serviceable Obtainable Market within the Dutch wind tunnel testing ecosystem and is projected to operate profitably at a rate of €25,000 per flight day. Operations will be based out of Den Helder Airport under the EASA SC-Light-UAS High-risk classification, with regulatory compliance maintained through the simultaneous acquisition of a Type Certificate and Design Organisation Approval (DOA), which allows internal certification of modifications made to the aircraft on a per experiment basis.
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This report details the design, engineering, and commercial feasibility of the High-speed Unmanned General-purpose Observatory (HUGO), a 50 kg modular transonic flying laboratory. HUGO aims to address the gap between scale wind-tunnel testing and full-scale flight validation. Operating primarily at Mach 0.75, HUGO bypasses the wall-interference limitations of conventional transonic wind tunnels and the severe safety risks associated with manned flight testing. To meet its experimental objectives, the finalized airframe features a high-wing, T-tail configuration with a modular wing, canard and empennage ports and retractable steel landing gear. A defining feature of the platform is its customizable "Planform Envelope," which allows clients to interchange main wing configurations with aspect ratios ranging from 5 to 27, as well as various sweeps, chords and thickness profiles. To cost-effectively produce in low volumes, while maximizing structural efficiency, the airframe utilizes a composite monocoque structure capable of safely withstanding ultimate load factors of up to 9g. Propulsion is provided by twin fuselage-mounted JetCat P100-RX-BL micro-turbines, enabling HUGO to execute a 30-minute nominal mission that includes a five-minute Mach 0.75 test segment at FL270. Because high-fidelity data collection is the core value proposition of a flying laboratory, the aircraft is equipped with a comprehensive payload suite, including dual LIDAR wing deflection sensors, 16 surface-mounted strain gauges, and 6-axis load cells, to isolate and measure aerodynamic forces. Commercially, HUGO targets a €14.2 million Serviceable Obtainable Market within the Dutch wind tunnel testing ecosystem and is projected to operate profitably at a rate of €25,000 per flight day. Operations will be based out of Den Helder Airport under the EASA SC-Light-UAS High-risk classification, with regulatory compliance maintained through the simultaneous acquisition of a Type Certificate and Design Organisation Approval (DOA), which allows internal certification of modifications made to the aircraft on a per experiment basis.
Experimental Study on Tollmien-Schlichting Waves over a Sharp-Edged Rectangular Bump
A study on harmonic content and wave growth
Surface imperfections on laminar aircraft surfaces, such as panel joints and discontinuities, can strongly modify boundary-layer stability. Sharp-edged rectangular bumps (SERBs) combine two widely studied surface features, the Forward-Facing Step (FFS) and a Backward-Facing Step (BFS), and provide a useful geometry for examining how step-induced mean-flow distortion and separation affect the development of Tollmien-Schlichting (TS) waves. However, previous studies on similar bump shapes have mostly considered a single incoming TS-wave amplitude, leaving the dependence of the SERB-induced boundary-layer response on incoming TS-wave amplitude insufficiently resolved.
To investigate how the boundary-layer response to a SERB depends on the amplitude of an incoming forced TS wave, this work combined numerical stability analysis with experiments performed on an unswept flat plate in the low-turbulence environment of the anechoic wind tunnel (A-tunnel) at TU Delft. Dielectric-Barrier Discharge (DBD) plasma actuators were used to force single-frequency TS-wave disturbances while allowing for easy amplitude variation. Surface microphones and Hot-Wire Anemometry (HWA) measurement systems were used to collect data to analyse the harmonic content of the disturbance, its wall-normal structure at the forcing frequency, and its downstream growth, comparing across the clean flat plate with and without the SERB installed over a range of forcing amplitudes. Independent monitoring of forcing consistency was shown to be important in long-duration plasma-forced experiments, where maintaining a consistent forcing amplitude is required. Simultaneous microphone measurements were necessary to distinguish genuine flow-induced amplification from transient variations in actuator output.
The results show that the influence of the SERB is strongly region-dependent: the forced TS-wave behaves like the clean case upstream of the bump and undergoes local amplification in the regions immediately upstream of the FFS and in the region just downstream of the FFS lip, a reduction in growth rate and stabilisation over the bump, and greater amplification downstream of the BFS. Greater forcing amplitudes are associated with a broader redistribution of spectral energy in the wall-normal direction and an earlier loss of a distinct shear-layer instability signature introduced in the recirculation region behind the BFS. The SERB, therefore, does not behave as a simple amplifier of TS waves, but instead produces a region-dependent response, with local amplification ahead of the FFS, reduced growth over the bump, and stronger re-amplification downstream of the BFS, where the response becomes increasingly sensitive to the amplitude of the incoming disturbance. ...
To investigate how the boundary-layer response to a SERB depends on the amplitude of an incoming forced TS wave, this work combined numerical stability analysis with experiments performed on an unswept flat plate in the low-turbulence environment of the anechoic wind tunnel (A-tunnel) at TU Delft. Dielectric-Barrier Discharge (DBD) plasma actuators were used to force single-frequency TS-wave disturbances while allowing for easy amplitude variation. Surface microphones and Hot-Wire Anemometry (HWA) measurement systems were used to collect data to analyse the harmonic content of the disturbance, its wall-normal structure at the forcing frequency, and its downstream growth, comparing across the clean flat plate with and without the SERB installed over a range of forcing amplitudes. Independent monitoring of forcing consistency was shown to be important in long-duration plasma-forced experiments, where maintaining a consistent forcing amplitude is required. Simultaneous microphone measurements were necessary to distinguish genuine flow-induced amplification from transient variations in actuator output.
The results show that the influence of the SERB is strongly region-dependent: the forced TS-wave behaves like the clean case upstream of the bump and undergoes local amplification in the regions immediately upstream of the FFS and in the region just downstream of the FFS lip, a reduction in growth rate and stabilisation over the bump, and greater amplification downstream of the BFS. Greater forcing amplitudes are associated with a broader redistribution of spectral energy in the wall-normal direction and an earlier loss of a distinct shear-layer instability signature introduced in the recirculation region behind the BFS. The SERB, therefore, does not behave as a simple amplifier of TS waves, but instead produces a region-dependent response, with local amplification ahead of the FFS, reduced growth over the bump, and stronger re-amplification downstream of the BFS, where the response becomes increasingly sensitive to the amplitude of the incoming disturbance. ...
Surface imperfections on laminar aircraft surfaces, such as panel joints and discontinuities, can strongly modify boundary-layer stability. Sharp-edged rectangular bumps (SERBs) combine two widely studied surface features, the Forward-Facing Step (FFS) and a Backward-Facing Step (BFS), and provide a useful geometry for examining how step-induced mean-flow distortion and separation affect the development of Tollmien-Schlichting (TS) waves. However, previous studies on similar bump shapes have mostly considered a single incoming TS-wave amplitude, leaving the dependence of the SERB-induced boundary-layer response on incoming TS-wave amplitude insufficiently resolved.
To investigate how the boundary-layer response to a SERB depends on the amplitude of an incoming forced TS wave, this work combined numerical stability analysis with experiments performed on an unswept flat plate in the low-turbulence environment of the anechoic wind tunnel (A-tunnel) at TU Delft. Dielectric-Barrier Discharge (DBD) plasma actuators were used to force single-frequency TS-wave disturbances while allowing for easy amplitude variation. Surface microphones and Hot-Wire Anemometry (HWA) measurement systems were used to collect data to analyse the harmonic content of the disturbance, its wall-normal structure at the forcing frequency, and its downstream growth, comparing across the clean flat plate with and without the SERB installed over a range of forcing amplitudes. Independent monitoring of forcing consistency was shown to be important in long-duration plasma-forced experiments, where maintaining a consistent forcing amplitude is required. Simultaneous microphone measurements were necessary to distinguish genuine flow-induced amplification from transient variations in actuator output.
The results show that the influence of the SERB is strongly region-dependent: the forced TS-wave behaves like the clean case upstream of the bump and undergoes local amplification in the regions immediately upstream of the FFS and in the region just downstream of the FFS lip, a reduction in growth rate and stabilisation over the bump, and greater amplification downstream of the BFS. Greater forcing amplitudes are associated with a broader redistribution of spectral energy in the wall-normal direction and an earlier loss of a distinct shear-layer instability signature introduced in the recirculation region behind the BFS. The SERB, therefore, does not behave as a simple amplifier of TS waves, but instead produces a region-dependent response, with local amplification ahead of the FFS, reduced growth over the bump, and stronger re-amplification downstream of the BFS, where the response becomes increasingly sensitive to the amplitude of the incoming disturbance.
To investigate how the boundary-layer response to a SERB depends on the amplitude of an incoming forced TS wave, this work combined numerical stability analysis with experiments performed on an unswept flat plate in the low-turbulence environment of the anechoic wind tunnel (A-tunnel) at TU Delft. Dielectric-Barrier Discharge (DBD) plasma actuators were used to force single-frequency TS-wave disturbances while allowing for easy amplitude variation. Surface microphones and Hot-Wire Anemometry (HWA) measurement systems were used to collect data to analyse the harmonic content of the disturbance, its wall-normal structure at the forcing frequency, and its downstream growth, comparing across the clean flat plate with and without the SERB installed over a range of forcing amplitudes. Independent monitoring of forcing consistency was shown to be important in long-duration plasma-forced experiments, where maintaining a consistent forcing amplitude is required. Simultaneous microphone measurements were necessary to distinguish genuine flow-induced amplification from transient variations in actuator output.
The results show that the influence of the SERB is strongly region-dependent: the forced TS-wave behaves like the clean case upstream of the bump and undergoes local amplification in the regions immediately upstream of the FFS and in the region just downstream of the FFS lip, a reduction in growth rate and stabilisation over the bump, and greater amplification downstream of the BFS. Greater forcing amplitudes are associated with a broader redistribution of spectral energy in the wall-normal direction and an earlier loss of a distinct shear-layer instability signature introduced in the recirculation region behind the BFS. The SERB, therefore, does not behave as a simple amplifier of TS waves, but instead produces a region-dependent response, with local amplification ahead of the FFS, reduced growth over the bump, and stronger re-amplification downstream of the BFS, where the response becomes increasingly sensitive to the amplitude of the incoming disturbance.