VKI Seminar Series 2023
Free registration in respect with the VKI eligibility criteria. You will receive the information to join the seminar of your choice after the registration.
Single shot coherent Rayleigh-Brillouin scattering: Neutral gas & plasma flow multi-point thermodynamic characterization (temperature, density and flow velocity) in a non-resonant, non-intrusive and seed-less way. (open to public)
Guest Speaker: Dr. Alexandros Gerakis Senior Research & Technology Associate, Luxembourg Institute of Science and Technology
Metrology is a founding pillar and a driving force of scientific discovery and understanding. Albeit its key importance in all aspects of science and engineering, the field is still dominated by the use of mechanical, intrusive probes for flow velocity and pressure measurements. To tackle the matter, which is of key importance to the development of a plethora of science and engineering fields, our group is developing single shot coherent Rayleigh-Brillouin scattering (CRBS) as an alternative, non-intrusive probe for neutral and plasma flow thermodynamic characterization.
CRBS is a four-wave mixing diagnostic technique that relies on the creation of an optical lattice in a medium due to the interaction between polarizable particles and intense laser fields. Single shot CRBS1 has been demonstrated to be the coherent analog of spontaneous Rayleigh-Brillouin scattering in measuring the temperature, pressure, bulk and shear viscosity, speed of sound and polarizability of a gas or gas mixture2, as well as nanoparticles produced in an arc discharge3. In this talk, an overview on the theory and experimental aspects of single shot CRBS will be presented along with our recent work in measuring simultaneously the temperature, density (and thus the pressure) and flow velocity4,5 of neutral species in a neutral gas flow and radially across a glow discharge. Finally, the feasibility and working progress towards the use of CRBS as a thermodynamic characterization technique for partially/fully ionized gases as well as of liquid flows will be discussed.
References
- Gerakis, A., Shneider, M. N., and Barker, P. F., “Single-shot coherent Rayleigh-Brillouin scattering using a chirped optical lattice,” Opt. Lett., Vol. 38, No. 21, 2013, pp. 4449–4452.
- Gerakis, A., Shneider, M. N., and Stratton, B. C., “Remote-sensing gas measurements with coherent Rayleigh-Brillouin scattering,” Applied Physics Letters, Vol. 109, No. 3, 2016, p. 31112.
- Gerakis, A., Yeh, Y.-W., Shneider, M. N., Mitrani, J. M., Stratton, B. C., and Raitses, Y., “Four-Wave-Mixing Approach to In Situ Detection of Nanoparticles,” Phys. Rev. Applied, Vol. 9, 2018, p. 014031.
- Gerakis, A., Bak, J., Randolph, R., Shneider, M. N., “Demonstration of single shot laser velocimetry with coherent Rayleigh-Brillouin scattering”, AIAA Scitech 2021 Forum, 2021, p. 0224.
- Gerakis, A., Bak, J., Randolph, R., Shneider, M. N., “Seedless, non-resonant gas flow velocimetry with single shot coherent Rayleigh-Brillouin scattering”, Phys. Rev. Applied, Manuscript accepted
OpenFOAM seminar (online / on-site - open to public)
The event aims to bring together OpenFOAM users as well as those interested in potential applications of the code, both for academic and industrial purposes. The seminar will be held in hybrid mode, and it will be organized in the following way:
- 15:00 - Welcome and roundtable
- 15.30 - Session on “Introduction to the deformable overset method for the simulation of flexible and moving bodies” by Romain Poletti, von Karman Institute
Wind turbine blades, tube bundles in nuclear reactors, bird wings, etc. can all experience large motion along with large deformation. CFD simulations of such applications rely on dynamic grids which must continuously adapt to preserve high-quality cells. The present OpenFOAM session introduces the overset method, the deforming mesh technique and demonstrates how their merging allows to simulate bodies with arbitrarily large motion and deformation. The developments are presented with a step-by-step tutorial on flapping and deforming airfoils in OpenFOAM v2012. The tutorial ends with post-processing tools for analyzing results and a brief introduction to coupling OpenFOAM with an open-source Fluid-Structure interaction solver. All code developments will be released on a GitHub link. - 16.30 - Small presentation of the von Karman Institute and their main applications of OpenFOAM
All the material to follow the tutorial will be provided to the participants during the event, and an online platform will be created to share material and create discussions.
The event will be organized four times a year and we would like to invite you to share your applications and implementations.
Aerothermal analysis of a vertical landing reusable launcher configuration by means of CFD (online - open to public)
Dr. Mariasole Laureti, aerothermodynamics engineer at the Institute of Aerodynamics and Flow Technology in Göttingen (DLR)
Abstract: The European space strategy aims at maintaining autonomous, reliable and cost-effective access to space. Reusability represents a possible approach for reducing costs and improving flexibility of European launch systems. Many projects aim to develop cutting-edge technologies for Vertical Take-off Vertical Landing (VTVL) Reusable Launch Vehicles (RLVs) which return to and land to Earth applying retro propulsion combined with Aerodynamic Control Surfaces (ACS), i.e. RETALT (Horizon 2020), RETPRO (ESA), and concepts for next-generation launch vehicles: CALLISTO (DLR-CNES-JAXA), THEMIS (ESA – large European consortium led by Ariane Group).
In the presentation, a reference Two Stage To Orbit (TSTO) RLV configuration, named RETALT1, developed in the framework of RETALT project, with a design similar to the SpaceX rocket ”Falcon 9”, is used to discuss aerothermodynamic challenges introduced by this new category of launchers.
The assessment of thermal loads, during the entire trajectory, is essential for the correct dimensioning of the thermal protection system and for sizing other important structural parts like aerodynamic control surfaces and landing legs. Due to the costs and limitations of ground-based testing for large scale vehicles these predictions rely intensively on numerical simulations (CFD). The need of aero-thermal databases, as a fast-response surrogate model for the aerothermodynamic heating, arises because of the practical impossibility of performing unsteady CFD analysis over the entire trajectory due to the large disparity of fluid mechanical and structural time scales. The construction of these databases is based on a representative set of CFD simulations which cover at least the flight regimes with significant thermal loads.
An analysis of representative CFD results is provided with the aim to show typical flow field phenomena and the resulting heating patterns occurring during the ascent flight and the atmospheric entry of RETALT1 vehicle.
Biography: Mariasole Laureti obtained the MSc and PhD at the Department of Aerospace and Mechanical Engineering at Sapienza University of Rome, working on the modelling and simulation of aero-acoustic phenomena in large aft-finocyl solid rocket motors.
She is currently employed at DLR – Institute of Aerodynamics and Flow Technology in Göttingen as aerothermodynamics engineer. Her main task is the assessment of aerodynamic properties and thermal loads occurring on reusable launch vehicles during the entire flight trajectory. She is also involved in project related to plasma-radar interaction and space debris.
Surging Flow for Wind Tunnel Flight Testing (online - open to public)
Dr. Nicholas Kay, Research Fellow, Mechanical Engineering – Aerodynamics & Control, University of Auckland, New Zealand
Abstract: Recreating real-world unsteady flows is critical to accurate wind tunnel testing. However, it can also be beneficial to instead decompose the flow into different frequency components, and assess system response at each frequency. Such a capability is possible with active flow control methods. In this work, a surging flow capability is developed for free-flight testing of Uninhabited Aerial Vehicles (UAVs). Retrofitted to a general-purpose wind tunnel, this represents a low-cost means of producing repeatable flow surges in a large test environment. The frequency and magnitude of the surges produced are assessed, and an example is given of its use for flight testing UAVs.
Biography: Nicholas received his PhD from the University of Auckland, New Zealand, in 2021, his thesis, “Aerodynamic Response of a Two-Dimensional Cambered Wing at Low Reynolds Numbers in Steady-State Onset Turbulence”, examining the unsteady aerodynamics of Low Reynolds Number Aerofoils, in the context of small, Uninhabited Aerial Vehicles (UAVs). As a Research Fellow with the Drone Technology Research Group at the University of Auckland, his current research involves the simulation and flight testing of multirotor UAVs in the wind tunnel environment.
10 Entrepreneurial Tips for Success - The Life of an InFLOWencer (online - open to public)
Jousef Mourad, APEX Marketing, he Netherlands
Abstract: Join renowned influencer, Jousef Murad, as he takes you on a journey through his business history, unveiling the mistakes he made so you can avoid them when starting your own entrepreneurial journey. In this thought-provoking talk, Jousef will delve into the depths of failed ideas, strategic blunders, and missed opportunities, providing valuable insights and lessons that can help the future of your business. Through compelling and engaging anecdotes, Jousef will empower you with the knowledge to identify and navigate potential pitfalls in your own entrepreneurial journeys. Attendees will gain a profound understanding of the key factors contributing to business failure, while simultaneously learning how to leverage these mistakes as stepping stones towards success.
Aerodynamic interactions in supersonic and hypersonic rarefied flows (online - open to public)
Dr. Vincente Cardona, ICARE, CNRS, France
Abstract: When a spacecraft re-enters Earth's atmosphere, or in the case of a destructive space debris re-entry, the problem of proximal bodies should be considered. In particular, shock/shock interferences (SSI) can occur and affect the structure of the spacecraft or the debris trajectory. Depending on the altitude, the objects velocity is hypersonic and they evolve in a rarefied environment, leading to predominant viscous effects. In order to better understand the impact of rarefaction level on SSI, an experimental study was conducted in the MARHy wind tunnel (ICARE, CNRS, France). SSI were obtained with the interaction of two spheres in supersonic and hypersonic low-density flows. Different relative positions were explored to identify various types of interferences occurring in these flows, characteristic of altitudes between 69 and 93 km. Results focus on the visualisation of the SSI, drag and lift forces, and wall pressures measurements. The analysis revealed an important contribution of the viscous effects on the impact of SSI and thus on the aerodynamics of the following sphere.
In the hypersonic case, for which the viscous effects are even greater due to a combination of hypervelocity and low density, the observation of SSI did not allow the identification of clear interference structures. It will be more appropriate to talk about shock/shock mixing layer with strong aerodynamic effects.
Experimental feedback control of separated and open-cavity flows with MEMS Technologies (online - open to public)
Dr. Thomas Arnoult, Institut d'électronique, de microélectronique et de nanotechnologie, IEMN
Abstract: Flow control is a multidisciplinary domain combining fluid dynamics, control theory and technology design, which aims at modifying a flow natural behaviour in order to obtain positive changes. Fluid dynamics helps understanding the physics of plants to be controlled and set the objectives to be reached, such as lift enhancement, drag or noise reduction or limiting induced structural vibrations. Control theory helps defining the most adapted control strategy to be employed in the case of reactive control. Technology design, based on fluid dynamics and control theory requirements, helps conceiving adapted actuating and sensing technologies. In this work closed-loop control of two canonical flow configurations is proposed: one targeting the control of a separated flow over a NACA 4412 plain flap and one focusing on the control of flow instabilities developing in an open-cavity flow. On the plain flap configuration, the control is implemented with conventional technologies but the focus is brought onto the implementation of two novel control laws, which successfully counter the development of the separated flow. Further measurements show the control robustness towards variations in the flow conditions. However, on such a configuration, one aims at modifying the flow mean properties without benefiting from the flow natural instabilities. The second case focuses on an open-cavity flow, on which control can benefit from the flow natural instabilities. Closed-loop control of this flow configuration is implemented with MEMS (Micro Electro Mechanical Systems) actuators and is based on the design of a controller using a structured H∞ approach. Closed-loop control experiments damp the open-cavity flow resonance by 13 dB and highlight the controller robustness properties.
Short Biography: Thomas Arnoult received the Engineering Degree from ISAE-ENSMA (Institut Supérieur de l’Aéronautique et de l’Espace-Ecole Nationale Supérieure de Mécanique et d’Aérotechnique) and a Degree of Master of Science in Aerospace Dynamics from the Cranfield University (United Kingdom). After graduation in December 2019, he obtained his PhD degree in Mach 2023 at the IEMN, UMR CNRS 8520 Institute, in partnership with the ONERA, the French Aerospace Lab, regarding the use of innovative micro-actuators and micro-sensors in active flow control strategies.