Stratégie de grille conforme octrée intersectées pour les Applications aux calculs Aéroacoustiques de LAGOON, Modèle de train d'Atterrissage, utilisant le Flow Solver CEDRE non structuré

International audienceAircraft noise is a societal concern and landing gears contribute significantly to the generated noise in approach and landing configurations. Landing gears are characterized by their complex geometry and numerous works have been carried out to develop and validate aeroacoustics simulations to predict the associated noise. Most of them associate a time resolved flow solution, to capture the acoustic sources, to an acoustic computation, to estimate the resulting far field noise. Due to the geometric complexity, unstructured grids are required and may necessitate meticulous work to optimize. In this context, Lattice Boltzmann Methods (LBM) have become popular as they propose to combine automatic grid generation and high CPU efficiency and produced remarked results. The automatic grid generation is facilitated by the use of advanced wall models that do not require resolution of complex details of boundary layer flow, ranging from attached to detached regimes, that are produced by the complex geometries and flow environment of landing gears. Navier-Stokes (NS) solvers on the contrary rely on precise boundary layer solution that require complex grids, even in the unstructured approach, to handle the attached boundary layer regimes, that require strong grid anisotropy, as well as detached regimes and their trailing flow, that require grid isotropy. The grid construction work can therefore become a complex process. The simplification of this process is then an important challenge for industrial applications. The present work details a multi-year effort at ONERA in that direction

Quantum error correction : an introductory guide

Quantum error correction protocols will play a central role in the realisation of quantum computing; the choice of error correction code will influence the full quantum computing stack, from the layout of qubits at the physical level to gate compilation strategies at the software level. As such, familiarity with quantum coding is an essential prerequisite for the understanding of current and future quantum computing architectures. In this review, we provide an introductory guide to the theory and implementation of quantum error correction codes. Where possible, fundamental concepts are described using the simplest examples of detection and correction codes, the working of which can be verified by hand. We outline the construction and operation of the surface code, the most widely pursued error correction protocol for experiment. Finally, we discuss issues that arise in the practical implementation of the surface code and other quantum error correction codes

Some HPC challenges for multi-physics extended CFD computations

International audienceAs the numerical simulations become more and more used for prediction and analysis of complex non stationary flows and as the computer architectures steadily evolve towards massively parallel, there is a real need to adapt computational codes to make them ready for intensive use in a HPC cluster environment. In the same time there is a strong tendency in the CFD community to enlarge the scope of computations by associating and possibly by directly coupling different physics in a unique computation. Such multi-physics computations open the way to needed sizing, analysis and optimization of complex systems. Common examples are fluid/solid interactions (conjugate heat transfer, aeroelasticity, aeromechanics), aeroacoustics, two-phase flows, combustion. This reality puts severe demands especially for multi-physics codes that are at stakes to provide HPC performances while addressing several physics that are discretized on the same computational domain. The CEDRE code developed at ONERA as the reference code for energetics and propulsion is particularly concerned by these challenges. The present version CEDRE 5.1 is already daily used on clusters with thousands cores with a very good scalability

Investigation on landing gear shallow round cavity flow field and noise signature

International audienceThe flow features and acoustic emission of the two-wheel simplified LAGOON landing gear shallow cavity are numerically investigated. This cavity presents several differences when compared to other academic cases, the most important one is the flow detachment occurring before the cavity edge, generating a shear layer that develops over the cavity. Despite this difference, several agreements with academic studies of round cavities have been found in terms of incoming boundary layer characteristics, detached shear layer growth, and recirculation of the flow in the cavity. Furthermore a spectral analysis of the flow identified a vortex roll-up mechanism and its associated frequency in the shear layer. Finally the far-field noise emission of the cavity has been found to be broadband with the emergence of several narrow frequency contributions whose possible mechanisms of noise generation are discussed

Application of a High Order Finite Volume Scheme on Unstructured Grids to Fluid Dynamics and Aerothermochemistry

This paper presents a high order finite volume scheme built on a new k-exact reconstruction algorithm for general unstructured grids. The algorithm is capable of computing accurate polynomial approximations using data from adjacent cells only, overcoming a major obstacle to extend classical finite volume schemes beyond 2 nd order spatial accuracy. Moreover, it can easily be integrated in a cell or vertex centered finite volume method that uses the cell averages as the only unknown per grid cell and physical quantity. It is therefore particularly suited to upgrade existing 2 nd order finite volume solvers to higher accuracy without huge efforts in software development. Three numerical test cases demonstrate the viability of the scheme in practical applications. This work was announced in [13, 14]