776 Works

DRAGON, a flexible, visible-light AO testbed

Stephen Rolt, Alastair Basden, Nazim Bharmal, Nigel Dipper, Deli Geng, Tim Morris, Richard Myers & Andrew Reeves
DRAGON is the Durham University astronomical adaptive optics test-bench, designed to accurately simulate the effects of the atmosphere for the purposes of developing high-order adaptive optics, but principally targeted towards visible AO correction for current telescopes. The design consists of altitude adjustable phase screens, a synthetic sodium guide star and a set of fixed targets that can also be used as natural guide stars. The design has been optimised for both wide-field (2.5′ FoV, hence...

Smoke oxide particles formation at the burning surface of condensed systems

Valery BABUK & Nikita BUDNYI
Main positions of the mathematical model of smoke oxide particles (SOPs) formation at the burning surface of condensed system are developed. The model includes description of SOPs formation during burning of non-agglomerating metal in gas phase near surface of the burning condensed system, and during burning of metal of agglomerating particles on the surface of skeleton layer. Results and perspectives of using the model are considered for two different condensed systems (based on active binder...

State-resolved models of chemical reactions for non-equilibrium flow simulations

In this paper, the assessment of existing theoretical models for the vibrational state-resolved Zeldovich exchange reaction is carried out on the basis of comparison with the results of several quasi-classical trajectory (QCT) calculations. An error in the theoretical model proposed by Aliat is corrected; after correction this model provides a very good agreement with the QCT reaction rate coefficients. Then the model is further generalized in order to take into account the vibrational state of...

Reconfiguration control method for non-redundant actuator faults on UAV

Adele BOCHE, Jean-Loup FARGES & Henry DE PLINVAL
In this article, an indirect continuous and discrete Fault Tolerant Control scheme is applied to the longitudinal dynamics of a fixed-wing UAV. To address the problem raised by a possible engine fault, the FTC method is adapted to non-redundant actuator faults by considering signatures on residuals, designing discounted cost optimal controllers, using rolling horizon techniques and considering actuator dynamics in the state equation. The efficiency of the proposed approach is demonstrated on a scenario involving...

Are integral controllers adapted to the new era of ELT adaptive optics?

J.-M. Conan, H.-F. Raynaud, C. Kulcsar, S. Meimon & G. Sivo
Entering the ELT era implies reconsidering adaptive optics concepts at all levels, including controller design. Concentrating mainly on temporal aspects, one may wonder if integral controllers remain an adequate solution.We recall for instance the impressive correction brought by Linear Quadratic Gaussian (LQG) controllers for the rejection of windshake and vibration components. Based on this experience, we present here a careful evaluation of the respective performance of integrator versus LQG control on turbulent modes both in...

LGS WFS on ELTs II:Impact if the sodium layer fluctuations

S. Thomas, N. Muller, V. Michau & T. Fusco
The application of laser guide stars to large aperture telescopes has spurred many new studies in wavefront sensing. For the particular case of the Shack-HartmannWFS, wavefront sensing is prone to new sources of errors not previously considered. The primary source of error is spot elongation resulting from the resolution of the finite thickness of the sodium layer. The elongation spreads the signal over several pixels, resulting in a decrease of the signal to noise ratio...

Gain-Scheduled H Loop-Shaping Autopilot Design for Spin-Stabilized Canard-Guided Projectiles

Florian Seve, Spilios Theodoulis, Philippe Wernert, Michel Zasadzinski & Mohamed Boutayeb
This article is dedicated to the design of a complete guidance control system for the roll/pitch/yaw-channels of a 155 mm dual-spin projectile equipped with nosemounted trajectory correction canards. The projectile airframe parameter-dependent nonlinear model including aerodynamic and actuator/sensor uncertainty descriptions is given and the subsequently computed linearized models necessary for autopilot design are presented. The itch/yaw-channel dynamics linearized system is useful for highlighting important properties specific to these dynamics, in particular in relation with the...


This paper presents and substantiates the method of processing of the experimental data obtained from the experiments related to air sparging through the jet fuel layer. The experimental data was collected by Henshaw and Lam during the study addressed to oxygen re-absorption characteristics of an oxygen depleted, quiescent body of Jet A-1 fuel when sparged with air. In this study we accepted the hypothesis that the experimental results should be described primarily based on physical...

Advanced Aerodynamic Applications with the elsA Software

J. Reneaux, P. Beaumier & P. Girodroux-Lavigne
Numerical simulation capability is one key differentiating factor in designing efficient transportation systems. With advanced numerical simulation capabilities, complex phenomena involved can be taken into account. This is illustrated in this paper through several research studies. All the simulations were carried out with the elsA software developed at Onera. In terms of performance prediction, the capabilities of the CFD software are highlighted with various applications related to aircraft drag, control surface efficiency, high-lift configuration performance...

Fast Aerodynamic Establishment of a Constellation of CubeSats

Brenton SMITH, Melrose BROWN & Russell BOYCE
The lack of long-duration propulsion has seen CubeSat constellation operators resort to aerodynamic accelerations to establish their constellations. By utilising a discrete set of maximum and minimum drag, current algorithms have demonstrated a great deal of competency in establishing constellations. Built upon these methods, a new algorithm is proposed for constellation establishment that makes use of intermediate drag accelerations - not just maximum and minimum drag. In doing so, the new algorithm reduces the maximum...

MOAO Real-Time LQG implementation on CANARY

G. Sivo, C. Kulcsar, H.-F. Raynaud, J.-M. Conan, E. Gendron & F. Vidal
Single Conjugated Adaptive Optics is a proven technique used in order to correct the effect of atmospheric turbulence and telescope vibrations. The corrected field of view (FoV) is however limited by the anisoplanatism effect. Many concepts of Wide Field AO (WFAO) systems are under study, especially for the design of Extremely Large Telescopes (ELTs) instruments. Multi-Object Adaptive Optics (MOAO) is one of these WFAO concepts that is particularly suited for high redshifts galaxies observations in...

Challenges for Quantitative Astronomy with ELTs

M. Schoek, P. Hickson & B. Ellerbroek
Extremely large telescopes will push the limits of astronomical observations to a level not achievable with the current generation of telescopes. It will be possible to observe to fainter magnitude limits and, with adaptive optics, with higher angular resolution due to the sizes of the primary mirrors. In addition, it is expected that ”quantitative techniques” such as astrometry and photometry will achieve levels of accuracy not possible today. This requires controlling the error sources affecting...

ELT LGS-AO: Optimizing the LGS Return Flux

D. Bonaccini Calia, R. Holzlohner, I. Guidolin, F. Pedichini, M. Centrone, T. Kasper, G. Lombardi, W. Forth, S. Lewis, T. Pfrommer & W. Hackenberg
For the ELTs the use of AO with multiple sodium Laser Guide Stars will be routine. We think it is important to study the LGS generation in order to optimize the LGS-AO systems. It is in this context that we are working on the understanding and optimization of the laser parameters. In this paper we report on a part of our LGS return flux studies, aimed at identifying the optimal laser formats for CW and...

PERGOLA: an experimental facility to investigate storable propellants combustion

Bastien BOUST, Marc BELLENOUE, Stephane LAMORY, Emilie LABARTHE & Nathalie GIRARD
PPRIME Institute and CNES have initiated research activities to investigate the propulsion behaviour of liquid storable propellants, and the related phenomena: atomization of propellants, ignition ability, combustion stability, propulsion efficiency. For this purpose, a specific facility \"PERGOLA\" has been designed with high modularity, allowing physical diagnostics in a pressurized combustor featuring relevant flow conditions (a few hundred g/s, 5 MPa). The first results demonstrate the capability of PERGOLA facility and characterize the behaviour of a...

GRAIL: Green Solid Propellants for Launchers

Ammonium perchlorate (AP) is used in solid propellants for launchers. AP is in many ways an excellent oxidizer, but unfortunately it has a negative impact on the environment and on personal health. With ever increasing environmental concerns green solid propellants are desired. The aim of the EU funded project GRAIL is to determine if it is possible to replace AP with ammonium dinitramide (ADN) and ammonium nitrate (AN). An overview of the GRAIL project is...

BiGlobal stability analysis of the wake behind an isolated roughness element in hypersonic flow

Numerical results are presented for the stability analysis of the wake induced by a cuboidal roughness element mounted on a flat plate inside a Mach 6 freestream. Linear BiGlobal stability calculations are carried out for a single frequency on a spanwise plane located behind the roughness, using base flows obtained from laminar Navier-Stokes simulations. The results show that the Mack mode is the most unstable perturbation growing in the boundary layer, followed by varicose and...

Airborne Measurements of the Charge of Precipitating Particles Related to Radar Reflectivity and Temperature within two Different Convective Clouds

A. Delannoy & P. Gondot
Simultaneous ground based radar reflectivity measurements and airborne electric parameters (electrostatic field and charged particles) are presented. They are used to investigate the charging processes acting in convective cells. Within the two thunderclouds presented in this work, both signs are found on large hydrometeors. It is shown that negative particle charging exists at high levels in classical vertically developed cells. There is some evidence that positive charging of precipitating particles is occurring in the lower...

Mitigation of Reflected Shock Wave by Streamwise Plasma Array

Sergey LEONOV, Campbell CARTER, Alec HOUPT & Timothy OMBRELLO
This work focuses on the results of an experimental study of the Quasi-Direct-Current (Q-DC) electrical discharge impact on the shock-wave structure and wall-pressure distribution in a supersonic duct-driven airflow. A major attention is paid for the effect of plasma streamwise array on a reflection pattern of the impinging shock wave at interaction with the boundary layer.

Handling a highly structured and spatially variable Point Spread Function in AO images

Laura Schreiber, Emiliano Diolaiti, Michele Bellazzini, Paolo Ciliegi, Italo Foppiani, Laura Greggio, Barbara Lanzoni & Matteo Lombini
Adaptive Optics (AO) has become a key technology for all the main existing 8-meter class telescopes and it is considered a kind of enabling technology for future Extremely Large Telescopes. AO systems increase the energy concentration of the Point Spread Function (PSF), but the PSF itself is also characterized by complex shape and spatial variation. Efforts in the AO PSF modelling and in the integration of suitable models in a code for image analysis are...

A numerical mesoscale model for aluminum agglomeration in solid propellants

Mathieu PLAUD & Stany GALLIER
The formation of aluminum agglomerates during combustion of aluminized solid propellants is known to have a significant impact on the behavior of the motor. In this paper, we propose a phenomenological agglomeration model whose input data is obtained from a mesoscale solid propellant simulation code. This new coupling strategy is very promising since it has the potential to model various physical effects on agglomeration. First applications of the model on a typical industrial propellant show...

Prometheus, a LOX/LCH4 reusable rocket engine

Alessandra IANNETTI
Since 2015, ArianeGroup and CNES have initiated in strong partnership the development of a new low cost and reusable rocket engine to power the next generation of launchers after Ariane 6. Cryogenic rocket engine of 100tons class, it will run liquid oxygen and liquid methane. The Prometheus engine will have to meet ambitious design to cost approaches and still be capable of reusability. Equipped with a dedicated computer it will be able to perform thrust...

Probabilistic Approach to Damage Modeling of Aviation Composite Materials

Vyacheslav ASTANIN, Oleksii OLEFIR, Ganna SHCHEGEL & Andrii OLEFIR
Probabilistic model of damage calculation for aviation composite materials is proposed, the main task of which is physically substantiated modeling of stress dependence on deformations under the influence of external loading, distinguishing between the formed elastic and plastic deformation, as well as irreversible cracking and material destruction. For this purpose, the calculation of the probabilities of the destruction of bonds between the material elements, as well as the equivalent energy of deformation is made. Comparison...

Experiments on Plasma-Assisted Combustion in a Supersonic Flow : Optimization of Plasma Position in Relation to the Fuel Injector

Savelkin Konstantin, Yarantsev Dimitry & Leonov Sergey B
The results of an experimental study of plasma-induced ethylene ignition and flameholding in a supersonic model combustor are presented in the paper. The experimental combustor has a cross-section of 72 mm (width) x 60 mm (height) and length of 600 mm. The fuel is directly injected into the supersonic airflow through wall orifices. The flow parameters are : Mach number M=2, static pressure Pst=160-250 Torr, stagnation temperature T0=300 K and total air flow rate Gair0.9...

Surrogate Assisted Computation of the Parametric Safety Margin for a Flexible Launcher

Atul Kamath, Prathyush P Menon, Martine Ganet-Schoeller, Guillaume Maurice & Samir Bennani
In order to assess the robustness of dynamical systems, an approach is to demarcate the uncertain parameter space as safe set and unsafe set. Unsafe set represents the region within which the system lacks the required level of performance, or even loses its stability. However, determining the minimum distance metric for the unsafe set from the nominal operating point, the so-called parametric safety margin, for a higher dimensional dynamical system is not trivial and is...

Preliminary Study on Wall-modeled Large Eddy Simulation of Turbulent Heat Transfer for Liquid Rocket Engines

Wall-modeled large eddy simulation (WMLES) is performed toward simulation of turbulent heat transfer in liquid rocket engine flowfields. To assess the prediction capabilities of WMLES, as a preliminarily work, turbulent channel flows with heat transfer are simulated. The present results show that mean velocity and temperature profiles agree well with DNS and the log law from moderate to high Reynolds numbers. Outer-layer turbulence and its fluctuations of velocity and temperature are well captured with modeling...

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