Modélisation de la transition laminaire-turbulent par rugosité et bulbe de décollement laminaire sur les aubes de turbomachines

The goal of this thesis is to enhance laminar-turbulent transition modeling on high-lift lowpressure turbine blades. The presented transition modeling method relies on the Menter and Langtry transition model used in a RANS framework in the elsA solver.Once the model’s limits were clearly identified through a parametric study, we moved on to modification of the model. To do so, an optimization method was developed that allows recalibration of the model’s inner correlation functions. This new version of the model allows us to obtain modeling gains of about 20% on the VKI T106C cases through better capture of the separation-induced transition process.These previous computations correspond to ideal cases, for which surfaces may be considered as being smooth. However, we also have the need to consider more realistic surfaces for which roughness may influence the flow. Indeed, among those effects, is the potential influence of surface roughness on transition. In particular, if surface roughness induces transition up-stream of the smooth separation point, the separation bubble will be suppressed. Considering our efforts on modeling separation-induced transition with the Langtry model, it seemed natural to add roughness-induced transition modeling capacities to it. To do so, we implemented in the Langtry model a method developed by Stripf et al. to take into account surface roughness.Finally, the use of the Langtry transition model was extended to the k-l of Smith turbulence model. Indeed, this turbulence model is widely used in turbomachinery. In order that our works on transition modeling over turbine blades be more widely usable, we have completed this thesis by proposing an evolution of the transition model so that it may be used alongside the k-l model.L'objectif de cette thèse est de faire progresser la modélisation de la transition de couche limite sur des aubes de turbines basse-pression fortement chargées. Cette modélisation repose sur l'utilisation du modèle de transition de Menter et Langtry utilisé pour des calculs RANS dans le code elsA. Une fois les limitations du modèle de transition clairement identifiées par une étude sur la mise en données des calculs, nous avons entrepris de modifier ce dernier. Pour cela, un processus d'optimisation a été développé afin de permettre la recalibration des fonctions de corrélation internes au modèle de transition. Cette nouvelle version du modèle nous permet d'obtenir des gains sur la modélisation d'environ 20 % sur les cas T106C du VKI en capturant mieux la transition au sein du bulbe de décollement. Ces précédents calculs correspondent à des cas idéaux, où l'on peut considérer les surfaces comme étant lisses. Cependant, nous avons aussi un besoin de se rapprocher de surfaces plus réalistes pour lesquelles les rugosités peuvent avoir un impact sur l'écoulement. En effet, les rugosités de surface peuvent notamment avoir un effet sur la transition. En particulier, si les rugosités entraînent le déclenchement de la transition en amont du point de décollement laminaire théorique en surface lisse, ce décollement sera supprimé. Vu nos efforts pour améliorer la prévision de la transition par bulbe de décollement par le modèle de Langtry, il parait intéressant que celui-ci puisse prendre en compte l'état des surfaces. Pour cela, nous avons implanté une méthode de prévision de la transition sur surfaces rugueuses développée par Stripf et al. au sein du modèle de Langtry.Enfin, l'utilisation du modèle de transition de Langtry a été étendue au modèle de turbulence k-l de Smith. En effet, ce modèle est largement utilisé en turbomachine. Afin que nos travaux d'amélioration du modèle de transition pour les cas de turbine soit largement utilisables, nous avons complété cette thèse par une évolution du modèle de transition permettant son utilisation avec le modèle k-l de Smith

Performance of photosensors in a high-rate environment for gas Cherenkov detectors

The solenoidal large intensity device (SoLID) at Jefferson Lab will push the boundaries of luminosity for a large-acceptance detector, which necessitates the use of a light-gas threshold Cherenkov counter for online event selection. Due to the high luminosity, the single-photon background rate in this counter can exceed 160 kHz/cm$^2$ at the photosensors. Therefore, it is essential to validate the high-rate limits of the planned photosensors and readout electronics in order to mitigate the risk of failure. We report on the design and an early set of studies carried out using a small telescopic Cherenkov device in a high-rate environment up to 60 kHz/cm$^2$, in Hall C at Jefferson Lab. Commercially available multi-anode photomultipliers (MaPMT) and low-cost large-area picosecond photodetectors (LAPPD) were tested using the JLab FADC250 modules for readout. The test beam results show that the MaPMT array and the internal stripline LAPPD can detect and identify single-electron and pair-production events in high-rate environments. Due to its higher quantum efficiency, the MaPMT array provided a better separation between the single-electron and the pair-production events compared to the internal stripline LAPPD. A GEANT4 simulation confirms the experimental performance of our telescopic device.Comment: 16 pages, 11 figure

Modeling of roughness-indused and separation-indused laminar-turbulent transition of boundary layer on turbomachinery blades

L’objectif de cette thèse est de faire progresser la modélisation de la transition de couche limite sur des aubes de turbines basse-pression fortement chargées. Cette modélisation repose sur l’utilisation du modèle de transition de Menter et Langtry utilisé pour des calculs RANS dans le code elsA. Une fois les limitations du modèle de transition clairement identifiées par une étude sur la mise en données des calculs, nous avons entrepris de modifier ce dernier. Pour cela, un processus d’optimisation a été développé afin de permettre la recalibration des fonctions de corrélation internes au modèle de transition. Cette nouvelle version du modèle nous permet d’obtenir des gains sur la modélisation d’environ 20 % sur les cas T106C du VKI en capturant mieux la transition au sein du bulbe de décollement. Ces précédents calculs correspondent à des cas idéaux, où l’on peut considérer les surfaces comme étant lisses. Cependant, nous avons aussi un besoin de se rapprocher de surfaces plus réalistes pour lesquelles les rugosités peuvent avoir un impact sur l’écoule- ment. En effet, les rugosités de surface peuvent notamment avoir un effet sur la transition. En particulier, si les rugosités entraînent le déclenchement de la transition en amont du point de décollement laminaire théorique en surface lisse, ce décollement sera supprimé. Vu nos efforts pour améliorer la prévision de la transition par bulbe de décollement par le modèle γ-Rθt, il parait intéressant que celui-ci puisse prendre en compte l’état des surfaces. Pour cela, nous avons implanté une méthode de prévision de la transition sur surfaces rugueuses développée par Stripf et al. au sein du modèle γ-Rθt. Enfin, l’utilisation du modèle de transition γ-Rθt a été étendue au modèle de turbulence k-l de Smith.The goal of this thesis is to enhance laminar-turbulent transition modeling on high-lift low- pressure turbine blades. The presented transition modeling method relies on the Menter and Langtry transition model used in a RANS framework in the elsA solver. Once the model’s limits were clearly identified through a parametric study, we moved on to modification of the model. To do so, an optimization method was developed that allows recalibration of the model’s inner correlation functions. This new version of the model allows us to obtain modeling gains of about 20% on the VKI T106C cases through better capture of the separation-induced transition process. These previous computations correspond to ideal cases, for which surfaces may be considered as being smooth. However, we also have the need to consider more realistic surfaces for which roughness may influence the flow. Indeed, among those effects, is the potential influence of surface roughness on transition. In particular, if surface roughness induces transition up-stream of the smooth separation point, the separation bubble will be suppressed. Considering our efforts on modeling separation-induced transition with the γ-Rθt model, it seemed natural to add roughness-induced transition modeling capacities to it. To do so, we implemented in the γ-Rθt model a method developed by Stripf et al. to take into account surface roughness. Finally, the use of the γ-Rθt transition model was extended to the k-l of Smith tur- bulence model. Indeed, this turbulence model is widely used in turbomachinery. In order that our works on transition modeling over turbine blades be more widely usable, we have completed this thesis by proposing an evolution of the transition model so that it may be used alongside the k-l model

MEASUREMENT OF ELECTRON AND HOLE MOBILITIES PERPENDICULAR TO THE INTERFACE OF GaAs/GaAlAs SUPERLATTICES

Il est rapporté une série de mesures de la mobilité des électrons et des trous, perpendiculaire aux plans des couches dans des superréseaux GaAs/GaAlAs ayant des épaisseurs de barrières de 24 Å et 67 Å. L'interprétation des résultats expérimentaux, obtenus par une technique de temps de vol, s'appuie sur un modèle utilisant l'équation de Poisson couplée aux équations de dérive-diffusion. Les valeurs sont en accord avec une conduction de type minibande dans le cas des faibles épaisseurs de barrières ; pour des grandes barrières, plusieurs mécanismes sont suggérés.We report on measurements of the electron and hole mobilities perpendicular to interfaces of GaAs/GaAlAs superlattices. The superlattices are in intrinsic region of nin or pin structures and have two values of barrier thickness, 24 Å and 67 Å. The experimental results are associated to a numerical simulation using Poisson and drift-diffusion equations. The obtained values, for a small barrier, are in agreement with a conduction by miniband and, for a large barrier (at mid electric field) several effects are involved

DIY your captures when everything else fails: Description of an artisanal dart launcher with an assessment of the medium-term response in a primate

International audienceWhen our dart guns failed in Morocco, we devised an artisanal pressurised air launcher to replace them. The effective shooting range was between 12 and 20 m, which made it possible to capture wild Barbary macaques (Macaca sylvanus), from groups that would not allow for a closer approach or enter any trap. To assess the effect of that method of capture, we monitored the groups on foot before and after the captures. We looked for evidence of a change in risk perception after the captures. We did not uncover any such evidence in the step lengths, turning angles, home range area, frequency of rest while on the ground or frequency of social interactions. We conclude that for the study animals, being captured with our artisanal dart launcher, had a similar effect to being darted with a professional gun, and we intend this note as an inspiration to other field operators finding themselves in a similar predicament

Relation between Plasma Trough Concentration of Pazopanib and Progression-Free Survival in Metastatic Soft Tissue Sarcoma Patients

Background: Pazopanib (PAZ) is an oral angiogenesis inhibitor approved to treat soft tissue sarcoma (STS) but associated with a large interpatient pharmacokinetic (PK) variability and narrow therapeutic index. We aimed to define the specific threshold of PAZ trough concentration (Cmin) associated with better progression-free survival (PFS) in STS patients. Methods: In this observational study, PAZ Cmin was monitored over the treatment course. For the primary endpoint, the 3-month PFS in STS was analyzed with logistic regression. Second, we performed exposure–overall survival (OS) (Cox model plus Kaplan–Meier analysis/log-rank test) and exposure–toxicity analyses. Results: Ninety-five STS patients were eligible for pharmacokinetic/pharmacodynamic (PK/PD) assessment. In the multivariable analysis, PAZ Cmin < 27 mg/L was independently associated with a risk of progression at 3 months (odds ratio (OR) 4.21, 95% confidence interval (CI) (1.47–12.12), p = 0.008). A higher average of PAZ Cmin over the first 3 months was associated with a higher risk of grade 3–4 toxicities according to the NCI-CTCAE version 5.0 (OR 1.07 per 1 mg/L increase, CI95 (1.02–1.13), p = 0.007). Conclusion: PAZ Cmin ≥ 27 mg/L was independently associated with improved 3-month PFS in STS patients. Pharmacokinetically-guided dosing could be helpful to optimize the clinical management of STS patients in daily clinical practice

Comparison of Various CFD Codes for LES Simulations of Turbomachinery: From Inviscid Vortex Convection to Multi-Stage Compressor

peer reviewedSome possible future High Fidelity CFD codes for LES simulation of turbomachinery are compared on several test cases increasing in complexity, starting from a very simple inviscid Vortex Convection to a multistage axial experimental compressor. Simulations were performed between 2013 and 2016 by major Safran partners (Cenaero, Cerfacs, CORIA and Onera) and various numerical methods compared: Finite Volume, Discontinuous Galerkin, Spectral Differences. Comparison to analytical results, to experimental data or to RANS simulations are performed to check and measure accuracy. CPU efficiency versus accuracy are also presented. It clearly appears that the level of maturity could be different between codes and numerical approaches. In the end, advantages and disadvantages of every codes obtained during this project are presented

The Toxoplasma Dense Granule Proteins GRA17 and GRA23 Mediate the Movement of Small Molecules between the Host and the Parasitophorous Vacuole

SummaryToxoplasma gondii is a protozoan pathogen in the phylum Apicomplexa that resides within an intracellular parasitophorous vacuole (PV) that is selectively permeable to small molecules through unidentified mechanisms. We have identified GRA17 as a Toxoplasma-secreted protein that localizes to the parasitophorous vacuole membrane (PVM) and mediates passive transport of small molecules across the PVM. GRA17 is related to the putative Plasmodium translocon protein EXP2 and conserved across PV-residing Apicomplexa. The PVs of GRA17-deficient parasites have aberrant morphology, reduced permeability to small molecules, and structural instability. GRA17-deficient parasites proliferate slowly and are avirulent in mice. These GRA17-deficient phenotypes are rescued by complementation with Plasmodium EXP2. GRA17 functions synergistically with a related protein, GRA23. Exogenous expression of GRA17 or GRA23 alters the membrane conductance properties of Xenopus oocytes in a manner consistent with a large non-selective pore. Thus, GRA17 and GRA23 provide a molecular basis for PVM permeability and nutrient access

A Toxoplasma dense granule protein, GRA24, modulates the early immune response to infection by promoting a direct and sustained host p38 MAPK activation

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