Publications by Pénélope Leyland

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This paper presents a computational analysis on forced vibration fluid-structure interaction in compressible flow regimes. A so-called staggered approach is pursued where the fluid and structure are integrated in time by distinct solvers. Their interaction is then taken into account by a coupling algorithm. The unsteady fluid motion is simulated by means of an explicit time-accurate solver. For the fluid-structure interaction problems which are considered here the effects due to the viscosity can be neglect

Thermal protection systems (TPS) are of extreme importance for the survival of space vehicles especially during superorbital re-entry to Earth. The design of thermal protection systems requires in-depth knowledge of the thermal loading experienced during a re-entry. The thermal loading data is mostly determined using ground testing and can be backed up by modelling activities including computational fluid dynamics (CFD). The verification of this data with flight data is invaluable and a recent, rare example

Thermal protection systems (TPS) are employed for spacecraft to survive high temperature conditions during atmospheric re-entry. For space shuttle type re-entries, the use of ceramic tiles shield the payload from exposure to these high heat fluxes. Recent research into the use of low-density materials, such as alumina foams, brings its own scientific challenges, of which understanding internal heat transfer is one. To this end, the exact 3D geometry of their complex porous structures, before and after plasm

The characterization of non-thermal homogeneous plasmas is possible using optical emission spectroscopy (OES), notably by estimating the reduced electric field. This method was applied to characterize streamers generated by a nanosecond pulsed surface diel ...

The applications of surface dielectric barrier discharge plasma actuators, (DBD), have known a considerable interest recently in the field of flow control. In general, such actuators consist of two electrodes separated by an insulation covering the lower e ...

Space debris that re-enter the Earth's atmosphere can be partially or fully ablated along the trajectory path after hitting the atmosphere layers, once these become denser (approximately below 82 km). This paper combines re-entry survival analysis to by-pr ...

Experiments were conducted in order to investigate the ability of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators to control flow on airfoils in subsonic and transonic flow (up to Ma1 = 0.75, Re = 1.35 • 10^6). A NACA 0015 profile equipped with a leading edge mounted ns-DBD actuator was investigated up to Re = 2.3 • 10^5 (u1 = 24 m/s). Measurements of the surface pressure distribution clearly confirm the actuator’s potential to delay leading edge separation. In the following the impact on

In this work we apply the Continuation Multi-Level Monte Carlo (C-MLMC) algorithm proposed in Collier et al. (2014) to efficiently propagate operating and geometric uncertainties in inviscid compressible aerodynamics numerical simulations. The key idea of ...

The invention concerns a system of electrodes for generating a surface dielectric barrier discharge totally encapsulated in a ceramic dielectric, using co-fireable ceramic technology (ceramic tapes, LTCC, HTCC, green tapes). The plasma generation device ca ...

In the present study the interaction of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators with aerodynamic flow up to transonic velocities was investigated. The primary focus was on the influence of the flow on the discharge and the effects of the discharge itself. In addition, the influence of the ns-DBD on a shock-wave was studied. The aim was to improve the understanding of the plasma-flow interaction, a topic that is not yet fully understood, in particular for ns-DBD. The actuator was in

This work evaluates the changes in radiative properties of two decomposing carbonaceous porous materials, each composed of two semitransparent, homogeneous and isotropic phases. The understanding of the complex dependence of macroscopic optical behaviour o ...

A capsule entering a planetary atmosphere at hypersonic speeds experiences high levels of radiative heating. Furthermore, coupling between the ablation products from the surface of the vehicle and the high temperature gas can have a major effect on the head load experienced by the vehicle. This paper discusses a collaborative project aimed at better characterising the flow processes involved. A ground-based expansion tube facility is described in which radiation-ablation coupling is achieved through the use

Surface Dielelectric Barrier Discharges (DBD) are becoming very attractive in the field of flow control technologies for their promising effects on stabilising separating flows, at least at low speeds under the so-called ionic wind effect. Numerous experiments have been performed over the last few years to further study these effects. At high speeds, such as transonic aircraft or internal engine flow speeds, EPFL has performed studies showing a clear effect of the flow on the plasma, and a lesser effect on

Rebuilding of the experimental spectroscopy of Plasmatron and Plasma Torch data for an equivalent Titan atmosphere Chemistry ...

"Starting from the gas kinetic model, a new class of schemes for hyperbolic systems of conservation laws is presented. The flow solvers are based on the Boltzmann equations. The numerical discretization is based on the upwind cell vertex fluctuation-splitting model. The method is truly multidimensional in the sense that the splitting is independent of a particular normal direction; the geometry of the mesh does not influence the upwinding. Numerical results for inviscid flow test cases are presented to indi

Enhancing detached vortical flow over leading edges and flap surfaces allow high lift configurations in critical regimes of take-off and acceleration. In the context of the FP6 Environmentally Friendly High Speed Aircraft project HISAC, future high speed aircraft concepts were studied. Specific morphed leading edges were devised that are adapted to ultra-fine wing geometries, and enhance lift. Unsteady CFD and Wind Tunnel tests for low speed were based on the FP6 EPISTLE project (European Project for the Im

The mechanisms that should be considered for separation flow control applications of nanosecond pulsed dielectric barrier discharge (DBD) actuators were investigated on a NACA 0015 profile for velocities of 10 m/s (Re = 100, 000) and 20 m/s (Re = 200, 000) ...

The majority of problems in aircraft production and operation require decisions made in the presence of uncertainty. For this reason aerodynamic designs obtained with traditional deterministic optimization techniques seeking only optimality in a specific set of conditions may have very poor off-design performances or may even be unreliable. In this work, we present a novel approach for robust and reliability-based design optimization of aerodynamic shapes based on the combination of single and multi-objecti

In this work we apply the Continuation Multi-Level Monte Carlo (C-MLMC) algorithm proposed by [Collier et al, BIT 2014] to efficiently propagate operational and geometrical uncertainties in compressible aerodynamics numerical simulations. The key idea of MLMC is that one can draw MC samples simultaneously and independently on several approximations of the problem under investigations on a hierarchy of nested computational grids (levels). The expectation of an output quantity is computed as a sample average

The analysis of the risk from re-entry objects has become an important topic. Concerning the uncertainties and different flow regimes, the object-oriented tools have been developed and used for various re-entry mission scenarios because of the simplified c ...

Pénélope Leyland

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Analysis of Fluid-Structure Interaction by Means of Dynamic Unstructured Meshes

Ground to Flight Investigations of Hayabusa with Ablation Effects

Characterising Internal Heat Transfer in Thermal Protection Systems

OES Characterization of Steamers in a Nanosecond Pulsed SBDB Using N2 and Ar Transitions

High Voltage Pulsed DBD Effects on the Aerodynamic Performances and on the Shock Buffet

Re-entry survival analysis and ground risk assessment of space debris considering by-products generation

Experimental Investigation of Pulsed Dielectric Barrier Discharge Actuators in Sub- and Transonic Flow

A Continuation Multi Level Monte Carlo (C-MLMC) method for uncertainty quantification in compressible inviscid aerodynamics

LONG LIFETIME SYSTEM FOR THE GENERATION OF SURFACE PLASMAS

Investigation of Nanosecond Pulse Dielectric Barrier Discharges in Still Air and in Transonic Flow by Optical Methods

Tomography-based radiative characterisation of decomposing carbonaceous heat shield materials

Radiation-Ablation Coupling for Capsule Reentry Heating via Simulation and Expansion Tube Investigations

Surface DBD’s and plasma-flow interaction

TC4-2-Level 1: Rebuilding of Titan Atmosphere Plasma Radiation

New finite element based fluctuation splitting kinetic schemes

Vortical Flow Patterns for High Lift for High Speed Aircraft Concepts

Mechanisms of Control Authority by Nanosecond Pulsed Dielectric Barrier Discharge Actuators on Flow Separation

MATHICSE Technical Report : A continuation-multilevel Monte Carlo evolutionary algorithm for robust aerodynamic shape design

MATHICSE Technical Report : A continuation multi level Monte Carlo (C-MLMC) method for uncertainty quantification in compressible aerodynamics

A study on heat flux predictions for re-entry flight analysis