Добірка наукової літератури з теми "MARHy wind tunnel"

Purpose The purpose of this paper is to describe experimental and numerical investigations focussed on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a rarefied Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. The natural flow without actuation exhibits a shock wave with a hyperbolic shape. When the discharge is on, the shock wave shape remains hyperbolic but the shock wave is pushed forward, leading to an increase in the shock wave angle. In order to discriminate thermal effects from purely plasma ones, the plasma actuator is then replaced by an heating element. Design/methodology/approach The experimental study is carried out with the super/hypersonic wind tunnel MARHy located at the ICARE Laboratory in Orléans. The experimental configuration with the heating element is simulated with a code using the 2D full compressible Navier-Stokes equations adapted for the rarefied conditions. Findings For heating element temperatures equal to the flat plate wall surface ones with the discharge on, experimental and numerical investigations showed that the shock wave angle was lower with the heating element, only 50 percent of the values got with the plasma actuator, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed. The results obtained with the numerical simulations are then used to calculate the aerodynamic forces, i.e. the drag and the lift. These numerical results are then extrapolated to the plasma actuator case and it was found that the drag coefficient rises up to 13 percent when the plasma actuator is used, compared to only 5 percent with the heating element. Originality/value This paper matters in the topic of atmospheric entries where flow control, heat management and aerodynamic forces are of huge importance.

SummaryIn the Queen Mary College gust-tunnels, unsteady flows are generated by oscillating flaps attached to the downstream upper and lower surfaces of the contraction nozzle of a semi-open test section, open-return, low-speed wind-tunnel. The flow perturbations produced on the mainstream of velocityU∞, are of the travelling-wave type, with wave-velocityQ. Attention is drawn to the contradictory early measurements ofQ/U∞. New data are presented which showQ/U∞apparently diminishing along the tunnel axis from a high value near the nozzle exit to an asymptotic value of about 0·6 far downstream. Using a digital phase meter especially developed for the purpose it is shown that the explanation for this behaviour lies in the two-dimensional nature of the wave process in the region of the flaps.

This work presents an experimental investigation focused on the analysis of aerodynamic properties between two interacting spheres in a supersonic rarefied flow. Atmospheric re-entries of space debris, whether natural or man-made, begin at altitude 120 km, and observations of historical re-entries have shown that fragmentation occurs between 90 and 50 km. The resulting fragments interact with each other, altering their own trajectories while traversing the different flow regimes between the free molecular and continuum regimes. This study focuses on the intermediate slip regime, where viscous effects of varying magnitude can influence the nature of the interactions of the shocks and modify them from the already known behaviour in the continuum regime. Specifically, this study examines how two spheres interact with each other upon re-entry into the atmosphere, focusing particularly on the six types of shock/shock interactions identified by Edney. The experiments were performed in the MARHy wind tunnel, in a steady Mach 4 laminar flow with static pressure 2.67 Pa. To highlight the differences between the six types of interferences, a variety of set-ups and devices were used: flow-field visualization, aerodynamic forces (through two diagnoses, aerodynamic balance and the swinging sphere technique) and wall pressure measurements. Results demonstrate the identification of differences according to the type of interference observed, showing in particular the viscous effect of rarefied flows by making a comparison with the continuum regime.

L’objectif principal de ce travail de thèse est de caractériser expérimentalement l’impact des effets visqueux sur les performances aérodynamiques des planeurs hypersoniques. Cette étude regroupe six écoulements basse pression (de 0,068 Pa à 71,11 Pa) de la soufflerie MARHy, quatre supersoniques (Mach 2 et Mach 4) et deux écoulements hypersoniques (Mach 20). Les maquettes expérimentées sont au nombre de 6 et l’objectif est d’étudier des géométries avec des degrés d’optimisation différents et de comprendre l’impact des effets visqueux sur chacune d’elles. Différents diagnostics ont été utilisés pour mener à bien cette étude : Tout d’abord, une balance aérodynamique a été développée pour pouvoir mesurer les forces de traînée et de portance des différentes configurations. Ensuite, les ondes de choc ont été visualisées à l’aide de visualisation par décharge luminescente. Enfin, une étude de pression pariétale a été menée sur deux planeurs hypersoniques. Ce travail de thèse permet d’établir une large base de données expérimentales sur les planeurs hypersoniques en régime raréfié. Les études de forces ont permis de quantifier l’évolution de la finesse au cours d’une rentrée atmosphérique en fonction du degré de raréfaction (paramètre de Tsien). Pour ce qui est des angles d’attaque, des formulations tenant compte des effets visqueux ont été établies et pourront être utilisées lors de l’optimisation des waveriders à hautes altitudes. Un planeur hypersonique tenant compte de ces données a été testé et est prometteur à haute altitude. Tout au long de cette thèse, les résultats mettent en évidence l’impact des effets visqueux sur les performances aérodynamiques des planeurs hypersoniques
The main objective of this thesis work is to experimentally characterize the impact of viscous effects on the aerodynamic performance of hypersonic gliders. The study includes six low-pressure flows (ranging from 0.068 Pa to 71.11 Pa) from the MARHy wind tunnel, four supersonic flows (Mach 2 and Mach 4), and two hypersonic flows (Mach 20). A total of 6 models were tested, aiming to study geometries with different degrees of optimization and to understand the impact of viscous effects one ach of them. Various diagnostics were used to carry out this study : Firstly, an aerodynamic balance was developed to measure the drag and lift forces of the different configurations. Next, shock waves were visualized using glow discharge imaging. Finally, a parietal pressure study was carried out on two hypersonic gliders. This thesis work establishes a broad experimental database on hypersonic gliders in the rarefied regime. Force studies have enabled us to quantify the evolution of glide ratio during atmospheric re-entry as a function of the degree of rarefaction (Tsien parameter). As far as angles of attack are concerned, formulations taking viscous effects into account have been established and can be used in the optimization of high-altitude waveriders. A hypersonic glider incorporating these data has been tested and shows promise at high altitude. Throughout this thesis, results have highlighted the impact of viscous effects on the aerodynamic performance of hypersonic gliders