| 1. |
- Abreu, L. I., et al.
(författare)
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Wavepackets in turbulent flow over a NACA 4412 airfoil
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- Turbulent flow over a NACA 4412 airfoil with an angle of attack AoA = 5◦ was analysed using an incompressible direct numerical simulation (DNS) at chord Reynolds number of Rec = 4 · 105. Snapshots of the flow field were analysed using the method of Spectral Proper Orthogonal Decomposition (SPOD) in frequency domain, in order to extract the dominant coherent structures of the flow. Focus is given to two-dimensional disturbances, known to be most relevant for aeroacoustics. The leading SPOD modes show coherent structures forming a wavepacket, with significant amplitudes in the trailing-edge boundary layer and in the wake. To model coherent structures in the turbulent boundary layer, the optimal harmonic forcing and the associated linear response of the flow were obtained using the singular value decomposition of the linear resolvent operator. The resolvent analysis shows that the leading SPOD modes can be associated to most amplified, linearised flow responses. Furthermore, coherent structures in the wake are modelled as the Kelvin-Helmholtz mode from linear stability theory (LST).
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| 2. |
- Alfredson, J., et al.
(författare)
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Design of a distributed human factors laboratory for future air systems
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- This paper presents a rationale for structuring a distributed human factors laboratory for future air systems. The distributed herein refers to two aspects: content and geographic. As for content, the laboratory is structured in two levels, namely, individual, and team. As for geographic, the laboratory infrastructure is distributed in three physically separate facilities, namely, Department of Computer and Information Science (IDA) and Department of Management and Engineering (IEI) from Linköping University - Sweden and the Competence Center in Manufacturing from the Aeronautics Institute of Technology (ITA) - Brazil.
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| 3. |
- Hällqvist, Robert, 1983-, et al.
(författare)
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A Novel FMI and TLM-based Desktop Simulator for Detailed Studies of Thermal Pilot Comfort
- 2018
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Ingår i: ICAS congress proceeding. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Modelling and Simulation is key in aircraft system development. This paper presents a novel, multi-purpose, desktop simulator that can be used for detailed studies of the overall performance of coupled sub-systems, preliminary control design, and multidisciplinary optimization. Here, interoperability between industrially relevant tools for model development and simulation is established via the Functional Mockup Interface (FMI) and System Structure and Parametrization (SSP) standards. Robust and distributed simulation is enabled via the Transmission Line element Method (TLM). The advantages of the presented simulator are demonstrated via an industrially relevant use-case where simulations of pilot thermal comfort are coupled to Environmental Control System (ECS) steadystate and transient performance.
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| 4. |
- Morra, Pierluigi, et al.
(författare)
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Control of streaky disturbances in the boundary layer over a flat plate
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- The present work considers control of perturbations in the boundary layer over a flat plate by means of adaptive methods. In particular, we focus our attention on a control law based on a multi-input-multi-output (MIMO) filtered-x least-mean-square (fxLMS) adaptive algorithm. The studies are performed through direct numerical simulations. The perturbation field studied here mimics those generated by freestream turbulence with different amplitude and scales. Plasma actuators and shear-stress sensors are considered to mimic a real case scenario.
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| 5. |
- Nogueira, P. A. S., et al.
(författare)
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Resolvent-based control of streaks in boundary layers
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- In the present work, we investigate efficient placement of sensors and actuators for closed-loop control of boundary-layer flows. The focus of this work is on the transitional flow cases where perturbation field is dominated by streaks. This is done using a reduced-order model based on resolvent analysis, an approach that also allows us to analyse the sensitivity of the flow response to control. A numerical sensitivity analysis was performed in this first approach, leading to conclusions about best choices of velocity components to be sensed and directions to be forced. Afterwards, we compared the performance between gaussian and shear sensors at the wall, focusing on the damping of the first resolvent gain using these devices. We close the work with the analysis of a plasma actuator, a configuration closer to standard choices for this kind of problem in both simulations and experiments.
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| 6. |
- Papageorgiou, Athanasios, 1984-, et al.
(författare)
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Multidisciplinary Optimization of Unmanned Aircraft in a System of Systems Context
- 2018
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Ingår i: 31st Congress of The International Council of the Aeronautical Sciences (ICAS), September 9-14 2018, Belo Horizonte, Brazil.. - 9783932182884
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper explores the use of Multidisciplinary Design Optimization (MDO) in the development of Unmanned Aerial Vehicles (UAVs) when the requirements include a collaboration in a System of Systems (SoS) environment. In this work, the framework considers models that can capture the mission, stealth, and surveillance performance of each aircraft, while at the same time, a dedicated simulation module assesses the total cooperation effect on a given operational scenario. The resulting mixed continuous and integer variable problem is decomposed with a multi-level architecture, and in particular, it is treated as a fleet allocation problem that includes a nested optimization routine for sizing a “yet-to-be-designed” aircraft. Overall, the models and the framework are evaluated through a series of optimization runs, and the obtained Pareto front is compared with the results from a traditional aircraft mission planning method in order to illustrate the benefits of this SoS approach in the design of UAVs.
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| 7. |
- Sasaki, K., et al.
(författare)
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On the wave-cancelling nature of boundary layer transition control
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- This work deals with the feedforward active control of velocity fluctuations over incompressible 3D boundary layers. Two strategies are evaluated, the Linear Quadratic Gaussian (LQG) controller, built using the eigensystem realization algorithm (ERA), is compared to a wave-cancellation scheme, obtained via the direct inversion of the frequency-domain transfer functions of the system. For the evaluated cases, it is shown that LQG leads to a wave-cancelling signal of the incoming Tollmien-Schlichting wavepacket. Such result allows further insight into the physics behind the active control of convectively unstable flows permitting, for instance, the optimization of the transverse position for actuation via a linear stability approach.
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| 8. |
- Schminder, Jörg, 1982-, et al.
(författare)
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Pilot performance and heat stress assessment support using a cockpit thermoregulatory simulation model
- 2018
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Ingår i: ICAS congress proceeding. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Flights with high thermal loads inside the cockpit can have a considerable impact on pilot physiological and psychological performance resulting in thermal discomfort, dehydration and fatigue. In this work, a Functional Mock-up Interface (FMI) based aircraft system simulator is utilized with intent to compute and predict thermal comfort. The simulator can for example serve pilots as a tool for heat stress and flight risk assessment, supporting their pre-flight planning or be used by engineers to design and optimize cooling efficiency during an early aircraft design phase. Furthermore, the presented simulator offers several advantages such as map based thermal comfort analysis for a complete flight envelop, time resolved mental performance prediction, and a flexible composability of the included models.
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| 9. |
- Sobron, Alejandro, 1990-, et al.
(författare)
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Methods for efficient flight testing and modelling of remotely piloted aircraft within visual line-of-sight
- 2018
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Ingår i: Proceedings of the 31st Congress of The International Council of the Aeronautical Sciences (ICAS), September 9-14 2018, Belo Horizonte, Brazil.. - Bohn : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (refereegranskat)abstract
- Remotely piloted scaled models not only serve as convenient low-risk flying test-beds but also can provide useful data and increase confidence in an eventual full-scale design. Nevertheless, performing advanced flight tests in a safe and cost-effective manner is often a challenge for organizations with limited resources. A typical scenario is testing within visual line-of-sight at very low altitude, a type of operation that offers major cost advantages at the expense of a reduced available airspace. This paper describes some of the authors' work towards efficient performance evaluation and system identification of fixed-wing, remotely piloted aircraft under these challenging conditions. Results show that certain techniques, manoeuvre automation, and platform-optimised multisine input signals can improve the flight test efficiency and the modelling process. It is also probable that some of the benefits observed here could be extrapolated to flight testing beyond visual line-of-sight or even to full-scale flight testing.
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