A greenhouse study was conducted to determine the effects of deposition from static rocket test fires on corn and alfalfa. Seeds were germinated in a wide concentration range of depositional material, called test fire soil (TFS). Additionally, the impact of chloride and aluminum, two major components of test fire soil, on germination was also evaluated. Furthermore, plants were grown in packed columns and exposed to test fire soil, either in the root zone or on foliage. Tissue was weighed and analyzed to compare biomass production and plant composition. Corn and alfalfa exposed to test fire soil in the root zone produced less biomass than controls, but foliar treatment had no effect on biomass production. No kernels were produced by corn exposed to test fire soil in the root zone. Leaves of plants exposed to test fire soil in the root zone accumulated more metals and nutrients than controls, whereas plant tissue treated with test fire soil on the leaves contained only elevated levels of aluminum, although levels were still within reasonable concentrations for plants. Germination of seeds was not affected below 1% test fire soil in soil; however higher concentrations of test fire soil decreased percent germination. Addition of chloride to soil also inhibits germination, but addition of aluminum has no effect on germination percentage. Corn germination was restored in test fire soil leached with 200 mm artificial rainwater. The results of this research contribute information regarding the potential impact of test fire soil from static test fires on crop production. Test fire soil inhibits germination and growth if deposited in the root zone, and even foliar application alters tissue composition. However, plant composition is not altered significantly in terms of feed criteria, and germination can be restored by irrigating the TFS. The effects of test fire soil are attributed to high levels of chloride that induce salt stress. Crop damage may be avoided by conducting static test fires after crops are harvested or providing extra irrigation to soil impacted with the TFS.

The ability of a propulsion system is very crucial for the capability of a missile or a rocket system. Unlike liquid propellant rocket motors, the only control mechanism of the thrust value is the propellant geometry in solid propellant rocket motors. When the operation of solid propellant rocket motor has started, it cannot be stopped anymore. For this main reason the advance of dual pulse motor technology has started. The aim of this study is to investigate the geometrical effects of design parameters on the flow behavior of a dual pulse solid propellant rocket motor by using commercial Computational Fluid Dynamics (CFD) methods. For the CFD analysis, a generic dual pulse rocket motor model is constituted. Within this model, initially four different geometry alternatives of Pulse Separation Device (PSD) are analyzed. To begin PSD analyses, mesh sensitivity analyses are performed on one PSD geometry alternative. By defined grid size, the analyses of PSD geometry alternatives are performed. Computed results were compared in terms of flow behavior (flow streamlines, velocity distribution, turbulent kinetic energy&hellip / etc.) with each other. With the selected PSD geometry alternative the effects of L/D ratio (Length/Diameter ratio) of first pulse chamber, Achamb/APSD ratio (Chamber area/PSD opening area) and APSD/Ath ratio (PSD opening area/Throat area) on the flow behavior is investigated. Flow analyses are performed by simulating the unsteady flow of second pulse operation. With the performed analyses, it is aimed to identify generic geometric definitions for a dual pulse rocket motor.

Design process of a solid rocket motor with the objective of meeting certain mission requirements can be specified as a search for a best set of design parameters within the overall design constraints. In order to ensure that the best possible design amongst all achievable designs is being achieved, optimization is required during the design process. In this thesis, an optimization tool for internal ballistic design of solid rocket motors was developed. A direct search method Complex algorithm is used in this study. The optimization algorithm changes the grain geometric parameters and nozzle throat diameter within the specified bounds, finally achieving the optimum results. Optimization tool developed in this study involves geometric modeling of the propellant grain, burnback analysis, a 0-dimensional ballistic performance prediction analysis of rocket motor and the mathematical optimization algorithm. The code developed is verified against pretested rocket motor performance.

Control of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non-reacting experiment using a primary flow of air, where both the duct exit and inlet are choked, simulated the closed-end acoustics. Two plates, separated by 1.27 cm, produced the vortex shedding phenomenon at the chamber's first longitudinal mode. Two active control schemes, closed-loop and open-loop, were studied via a cold-flow simulation for validating the effects of reducing vortex shedding instabilities in the system. Actuation for both control schemes was produced by using a secondary injection method. The actuation system consisted of pulsing compressed air from a modifed, 2-stroke model airplane engine, controlled and powered by a DC motor. The use of open-loop only active control was not highly effective in reducing the amplitude of the first longitudinal acoustic mode, near 93 Hz, when the secondary injection was pulsed at the same modal frequency. This was due to the uncontrolled phasing of the secondary injection system. A Pulse Width Modulated (PWM) signal was added to the open-loop control scheme to correct for improper phasing of the secondary injection flow relative to the primary flow. This addition allowed the motor speed to be intermittently increased to a higher RPM before returning to the desired open-loop control state. This proved to be effective in reducing the pressure disturbance by approximately 46%. A closed-loop control scheme was then test for its effectiveness in controlling the phase of the secondary injection. Feedback of the system's state was determined by placing a dynamic pressure transducer near the chamber exit. Closed-loop active control, using the designed secondary injection system, was proven as an effective means of reducing the problematic instabilities. A 50% reduction in the FFT RMS amplitude was realized by utilizing a Proportional-Derivative controller to modify the phase of the secondary injection.

The present research project is carried out at the von Karman Institute for Fluid Dynamics (Rhode-Saint-Genèse, Belgium) with the financial support of the European Space Agency. The first stage of spacecrafts (e.g. Ariane 5, Vega, Shuttle) generally consists of large solid propellant rocket motors (SRM), which often consist of segmented structure and incorporate a submerged nozzle. During the combustion, the regression of the solid propellant surrounding the nozzle integration part leads to the formation of a cavity around the nozzle lip. The propellant combustion generates liquefied alumina droplets coming from chemical reaction of the aluminum composing the propellant grain. The alumina droplets being carried away by the hot burnt gases are flowing towards the nozzle. Meanwhile the droplets may interact with the internal flow. As a consequence, some of the droplets are entrapped in the cavity forming an alumina puddle (slag) instead of being exhausted through the throat. This slag reduces the performances. The aim of the present study is to characterize the slag accumulation process in a simplified model of the MPS P230 motor using primarily optical experimental techniques. Therefore, a 2D-like cold-gas model is designed, which represents the main geometrical features of the real motor (presence of an inhibitor, nozzle and cavity) and allows to approximate non-dimensional parameters of the internal two-phase flow (e.g. Stokes number, volume fraction). The model is attached to a wind-tunnel that provides quasi-axial flow (air) injection. A water spray device in the stagnation chamber realizes the models of the alumina droplets, which are accumulating in the aft-end cavity of the motor. To be able to carry out experimental investigation, at first the the VKI Level Detection and Recording(LeDaR) and Particle Image Velocimetry (PIV) measurement techniques had to be adapted to the two-phase flow condition of the facility. A parametric liquid accumulation assessment is performed experimentally using the LeDaR technique to identify the influence of various parameters on the liquid deposition rate. The obstacle tip to nozzle tip distance (OT2NT) is identified to be the most relevant, which indicates how much a droplet passing just at the inhibitor tip should deviate transversally to leave through the nozzle and not to be entrapped in the cavity. As LeDaR gives no indication of the driving mechanisms, the flow field is analysed experimentally, which is supported by numerical simulations to understand the main driving forces of the accumulation process. A single-phase PIV measurement campaign provides detailed information about the statistical and instantaneous flow structures. The flow quantities are successfully compared to an equivalent 3D unsteady LES numerical model. Two-phase flow CFD simulations suggest the importance of the droplet diameter on the accumulation rate. This observation is confirmed by two-phase flow PIV experiments as well. Accordingly, the droplet entrapment process is described by two mechanisms. The smaller droplets (representing a short characteristic time) appear to follow closely the air-phase. Thus, they may mix with the air-phase of the recirculation region downstream the inhibitor and can be carried into the cavity. On the other hand, the large droplets (representing a long characteristic time) are not able to follow the air-phase motion. Consequently, a large mean velocity difference is found between the droplets and the air-phase using the two-phase flow measurement data. Therefore, due to the inertia of the large droplets, they may fall into the cavity in function of the OT2NT and their velocity vector at the level of the inhibitor tip. Finally, a third mechanism, dripping is identified as a contributor to the accumulation process. In the current quasi axial 2D-like set-up large drops are dripping from the inhibitor. In this configuration they are the main source of the accumulation process. Therefore, additional numerical simulations are performed to estimate the importance of dripping in more realistic configurations. The preliminary results suggest that dripping is not the main mechanism in the real slag accumulation process. However, it may still lead to a considerable contribution to the final amount of slag.

Les moteurs à propergol solide sont parfois le siège d'instabilités aéroacoustiques résultant d'un couplage entre l'hydrodynamique des gaz brûlés et les modes acoustiques de la chambre de combustion. Ces instabilités se traduisent par de fortes Oscillations de Pression (ODP) dans la chambre de combustion du moteur. Ces ODP entrainent des vibrations de la structure, qui si elles venaient à dépasser certains niveaux pourraient nuire à la charge utile. Au vu du coût d'un essai, il est important de disposer d'outils permettant de prédire l'apparition de ces instabilités au moment de la conception. L'objectif de cette thèse est en premier lieu la mise au point d'une chaîne de couplage permettant d'évaluer l'impact des interactions fluide-structure sur l'amplitude des oscillations aéroacoustiques présentes au sein du propulseur. Une attention particulière est portée à l'algorithme de couplage entre les solveurs fluide et solide afin d'assurer une bonne conservation de l'énergie à l'interface fluide-structure, point clé dans l'étude d'instabilités. La chaîne numérique ainsi conçue est appliquée à une configuration réduite du moteur à propergol solide d'Ariane 5 dans le cadre de deux études. La première porte sur l'impact des vibrations de la structure sur les d'instabilités aéroacoustiques. L'effet d'un croisement de fréquences des modes propres longitudinaux de la structure et un des modes acoustiques de la chambre de combustion est traité. La seconde étude s'intéresse à l'effet des battements des protections thermiques du propulseur dans l'écoulement. Une structuration de l'écoulement et un net renforcement des ODP sont mis en évidence. / Large solid propellant rocket motors may be subjected to aero-acoustic instabilities arising from a coupling between the burnt gas flow and the acoustic eigenmodes of the combustion chamber. These instabilities lead to large pressure oscillations in the combustion chamber. These pressure oscillations cause vibrations which might jeopardize the payload if they happen to be larger than a certain threshold. Given the size and cost of any single firing test or launch, it is of first importance to rely on numerical tools able to predict these instabilities so that they can be avoided at the design level. The first purpose of this thesis is to build a numerical tool in order to evaluate how the coupling of the fluid flow and the whole structure of the motor influences the amplitude of the aeroacoustic oscillations living inside the rocket. A particular attention was paid to the coupling algorithm between the fluid and the solid solvers in order to ensure the best energy conservation through the interface.The numerical chain is applied to a sub-scaled configuration of Ariane 5 solid rocket motor in two studies. The first relates to the impact of vibration of the structure on aeroacoustic instabilities. The effect of a crossover frequency between the longitudinal modes of the structure and the acoustic modes of the combustion chamber is assessed. The second study examines the effect of thermal protection oscillations in the flow. An increased of the flow organisation and a significant strengthening of pressure oscillations are highlighted.

The focus of this study is the prediction of trajectories of solid particles injected into either a cylindrically- shaped solid rocket motor (SRM) or a bidirectional vortex chamber (BV). The Lagrangian particle trajectory is assumed to be governed by drag, virtual mass, Magnus, Saffman lift, and gravity forces in a Stokes flow regime. For the conditions in a solid rocket motor, it is determined that either the drag or gravity forces will dominate depending on whether the sidewall injection velocity is high (drag) or low (gravity). Using a one-way coupling paradigm in a solid rocket motor, the effects of particle size, sidewall injection velocity, and particle-to-gas density ratio are examined. The particle size and sidewall injection velocity are found to have a greater impact on particle trajectories than the density ratio. Similarly, for conditions associated with a bidirectional vortex engine, it is determined that the drag force dominates. Using a one-way particle tracking Lagrangian model, the effects of particle size, geometric inlet parameter, particle-to-gas density ratio, and initial particle velocity are examined. All but the initial particle velocity are found to have a significant impact on particle trajectories. The proposed models can assist in reducing slag retention and identifying fuel injection configurations that will ensure proper confinement of combusting droplets to the inner vortex in solid rocket motors and bidirectional vortex engines, respectively.

Within the scope of this thesis study, an optimization tool for the ballistic design of three-dimensional grains in solid propellant rocket motors is developed. The modeling of grain geometry and burnback analysis is performed analytically by using basic geometries like cylinder, cone, sphere, ellipsoid, prism and torus. For the internal ballistic analysis, a quasi-steady zero-dimensional flow solver is used. Genetic algorithms have been studied and implemented to the design process as an optimization algorithm. Lastly, the developed optimization tool is validated with the predesigned rocket motors.

Dans un moteur à propergol solide, l’écoulement dépend fortement des gouttes d’alumine en suspension, dont la fraction massique est élevée. La distribution en taille des gouttes, qui s’élargit avec la coalescence, joue un rôle clef. Or résoudre des écoulements diphasiques polydisperses instationnaires avec une bonne précision sur la taille est un défi à la fois sur le plan de la modélisation et du calcul scientifique: (1) de très petites gouttes, par exemple résultant de la combustion de nanoparticules d’aluminium, subissent mouvement brownien et coalescence, (2) de petites gouttes ont leur vitesse conditionnée par leur taille de sorte qu’elles coalescent lorsqu’elles ont des tailles différentes, (3) des gouttes plus grosses peuvent se croiser par effet d’inertie et (4) toutes les gouttes interagissent de manière fortement couplée avec la phase porteuse. En complément des approches lagrangiennes, des modèles eulériens ont été développés pour décrire la phase dispersée à un coût raisonnable, et ils permettent un couplage aisé avec la phase porteuse ainsi que la parallélisation massive des codes: les approches eulériennes sont bien adaptées aux calculs industriels. Le modèle Multi-Fluide permet la description détaillée de la polydispersion, des coreélations taille/vitesse et de la coalescence, en résolvant séparément des “fluides” de gouttes triées par taille, appelés sections. Un ensemble de modèles est évalué dans cette thèse et une stratégie numérique est développée pour effectuer des calculs industriels de moteurs à propergol solide. (1) La physique des nanoparticules est évalué et incluse dans un modèle de coalescence complet. Des méthodes de moments d’ordre élevé sont ensuite développées: (2) une méthode à deux moments en taille est étendue à la coalescence pour traiter la physique de la polydispersion et les développements numériques connexes permettent d’effectuer des calculs applicatifs dans le code industriel CEDRE; (3) une méthode basée sur les moments en vitesse du deuxième ordre, un schéma de transport à l’ordre deux sur maillages structurés ainsi qu’un modèle de coalescence sont développés. Des validations académiques de la stratégie pour gouttes d’inertie modérée sont effectuées sur des écoulements complexes puis avec de la coalescence; (4) une stratégie d’intégration en temps est développée et mise en œuvre dans CEDRE pour traiter efficacement le couplage fort, dans des cas instationnaires et polydisperses incluant de très petites particules. L’ensemble des développements est soigneusement validé: soit par des formules analytiques ad hoc pour la coalescence et pour le couplage fort d’une onde acoustique; soit par des comparaisons numériques croisées avec une DPS pour la coalescence et avec des simulations lagrangiennes de cas applicatifs, coalescents et fortement couplés; soit par des résultats expérimentaux disponibles sur une configuration académique de coalescence et sur un tir de moteur à échelle réduite. La stratégie complète permet des calculs applicatifs à un coût raisonnable. En particulier, un cal- cul de moteur avec des nanoparticules permet d’évaluer la faisabilité de l’approche et d’orienter les efforts de recherche sur les propergols chargés de nanoparticules. / In solid rocket motors, the internal flow depends strongly on the alumina droplets, which have a high mass fraction. The droplet size distribution, which is wide and spreads up with coalescence, plays a key role. Solving for unsteady polydisperse two- phase flows with high accuracy on the droplet sizes is a challenge for both modeling and scientific computing: (1) very small droplets, e.g. resulting from the combustion of nanoparticles of aluminum fuel, encounter Brownian motion and coalescence, (2) small droplets have their velocity conditioned by size so they coalesce when having different sizes, (3) bigger droplets have an inertial behavior and may cross each other’s trajectory, and (4) all droplets interact in a two-way coupled manner with the carrier phase. As an alternative to Lagrangian approaches, some Eulerian models can describe the disperse phase at a moderate cost, with an easy coupling to the carrier phase and with massively parallel codes: they are well-suited for industrial computations. The Multi- Fluid model allows the detailed description of polydispersity, size/velocity correlations and coalescence by separately solving “fluids” of size-sorted droplets, the so-called sections. In the present work, we assess an ensemble of models and we develop a numerical strategy to perform industrial computations of solid rocket motor flows. (1) The physics of nanoparticles is assessed and included in a polydisperse coalescing model. High order moment methods are then developed: (2) a Two-Size moment method is ex- tended to coalescence to treat accurately the physics of polydispersity and coalescence and the related numerical developments allow to perform applicative computations in the industrial code CEDRE; (3) a second order velocity moment method is developed, together with a second order transport scheme, to evaluate a strategy for a moderately inertial disperse phase, and academic validations are performed on complex flow fields; (4) a time integration strategy is developed and implemented in CEDRE to treat efficiently two-way coupling, in unsteady polydisperse cases including very small particles. The developments are carefully validated, either through purposely derived analytical formulae (for coalescence and two-way acoustic coupling), through numerical cross-comparisons (for coalescence with a Point-Particle DNS, for applicative cases featuring coalescence and two-way coupling with a Lagrangian method), or through available experimental results (for coalescence with an academic experiment, for the overall physics with a sub-scale motor firing). The whole strategy allows to perform applicative computations in a cost effective way. In particular, a solid rocket motor with nanoparticles is computed as a feasibility case and to guide the research effort on motors with nanoparticle fuel propellants.

Les lanceurs ont un impact sur la composition de l'atmosphere, et en particulier sur l'ozone stratospherique. Parmi tous les types de propulsion, les moteurs à propergol solide ont fait l'objet d'une attention particulière car leurs émissions sont responsables d'un appauvrissement significatif d'ozone dans le panache des lanceurs lors des premières heures suivant le lancement. Ce phénomène est principalement dû à la conversion de l'acide chlorhydrique, un composé chimique présent en grandes quantités dans les émissions de ce type de moteur, en chlore actif qui réagit par la suite avec l'ozone dans un cycle catalytique similaire à celui responsable du "trou de la couche d'ozone", cette diminution périodique de l'ozone en Antarctique. Cette conversion se produit dans le panache supersonique, où les hautes températures favorisent une seconde combustion entre certaines espèces chimiques du panache et l'air ambiant. L'objectif de cette étude est d'évaluer la concentration de chlore actif dans le panache d'un moteur à propergol solide en utilisant la technique des Simulations aux Grandes Echelles (SGE). Le gaz est injecté à travers la tuyère d'un moteur et une méthode de couplage entre deux instances du solveur de mécanique des fluides est utilisée pour étendre autant que possible le domaine de calcul derrière la tuyère (jusqu'à l'équivalent de 400 diamètres de sortie de la tuyère). Cette méthodologie est validée par une première SGE sans chimie, en analysant les caractéristiques de l'écoulement supersonique avec co-écoulement obtenu par ce calcul. Ensuite, le chimie mettant en jeu la conversion des espèces chlorées a été étudiée au moyen d'un modèle "hors-ligne" permettant de résoudre une chimie complexe le long de lignes de courant extraites d'un écoulement moyenné dans le temps résultant du calcul précédent (non réactif). Enfin, une SGE multi-espèces est réalisée, incluant un schéma chimique auparavant réduit afin de limiter le coût de calcul. Cette simulation représente une des toutes premières SGE d'un jet supersonique réactif, incluant la tuyère, effectuée sur un domaine de calcul aussi long. En capturant avec précision le mélange du panache avec l'air ambiant ainsi que les interactions entre turbulence et combustion, la technique des simulations aux grandes échelles offre une évaluation des concentrations des espèces chimiques dans le jet d'une precision inédite. Ces résultats peuvent être utilisés pour initialiser des calculs atmosphériques sur de plus larges domaines, afin de modéliser les réactions entre chlore actif et ozone et de quantifier l'appauvrissement en ozone dans le panache. / Rockets have an impact on the chemical composition of the atmosphere, and particularly on stratospheric ozone. Among all types of propulsion, Solid-Rocket Motors (SRMs) have given rise to concerns since their emissions are responsible for a severe decrease in ozone concentration in the rocket plume during the first hours after a launch. The main source of ozone depletion is due to the conversion of hydrogen chloride, a chemical compound emitted in large quantities by ammonium perchlorate based propellants, into active chlorine compounds, which then react with ozone in a destructive catalytic cycle, similar to those responsible for the Antartic "Ozone hole". This conversion occurs in the hot, supersonic exhaust plume, as part of a strong second combustion between chemical species of the plume and air. The objective of this study is to evaluate the active chlorine concentration in the far-field plume of a solid-rocket motor using large-eddy simulations (LES). The gas is injected through the entire nozzle of the SRM and a local time-stepping method based on coupling multi-instances of the fluid solver is used to extend the computational domain up to 400 nozzle exit diameters downstream of the nozzle exit. The methodology is validated for a non-reactive case by analyzing the flow characteristics of the resulting supersonic co-flowing under-expanded jet. Then the chemistry of chlorine is studied off-line using a complex chemistry solver applied on trajectories extracted from the LES time-averaged flow-field. Finally, the online chemistry is analyzed by means of the multi-species version of the LES solver using a reduced chemical scheme. To the best of our knowledge, this represents one of the first LES of a reactive supersonic jet, including nozzle geometry, performed over such a long computational domain. By capturing the effect of mixing of the exhaust plume with ambient air and the interactions between turbulence and combustion, LES offers an evaluation of chemical species distribution in the SRM plume with an unprecedented accuracy. These results can be used to initialize atmospheric simulations on larger domains, in order to model the chemical reactions between active chlorine and ozone and to quantify the ozone loss in SRM plumes.