Understanding Transonic Weapon Bay Flows

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Aeroelastic simulations of stores in weapon bays using Detached-Eddy simulation

Detached-Eddy Simulations of flows in weapon bays with a generic store at different positions in the cavity and with flexible fins are presented in this paper. Simulations were carried out to better understand the fluid–structure interactions of the unsteady, turbulent flow and the store. Mach and Reynolds numbers (based on the missile diameter) were 0.85 and 326.000 respectively. Spectral analysis showed few differences in the frequency content in the cavity between the store with rigid and flexible fins. However, a large effect of the store position was seen. When the store was placed inside the cavity, the noise reduction reached 7 dB close to the cavity ceiling. The closer the store to the carriage position, the more coherent and quieter was the cavity. To perform a more realistic simulation, a gap of 0.3% of the store diameter was introduced between the fin root and the body of the store. Store loads showed little differences between the rigid and flexible fins when the store was inside and outside the cavity. With the store at the shear layer, the flexible fins were seen to have a reduction in loads with large fluctuations in position about a mean. Fin-tip displacements of the store inside the cavity were of the range of 0.2% of the store diameter, and in the range of 1–2% of store diameter when at the shear layer

Multi-Disciplinary Simulations of Stores in Weapon Bays using Scale Adaptive Simulation

This paper presents a set of cavity flow calculations involving door opening, store release and aeroelasticity. Aeroelastic effects were present, but secondary for the case at hand. For established bay flows, the structural excitation showed a directional dependence, and the structures were responding to the flow frequency content. Maximum store deformations were of about 2% of the store diameter. This is the first time where such effects are quantified for store releases from within bays. The store deformation while interacting with the shear layer, and the store trajectory variability are also quantified

Multi-disciplinary simulations of stores in weapon bays using scale adaptive simulation

This paper presents cavity flow calculations using the scale-adaptive simulation method involving door opening, store release and aeroelas- ticity. For established bay flows, the structural excitation showed a directional dependence, and the structures were responding to the flow frequency content. Maximum store deformations were of about 2% of the store diameter during store release. This is the first time where such effects are quantified for stores released from within bays. The store deformation, the role of the shear layer, and the store trajectory variability are also quantified

Store release trajectory variability from weapon bays using scale-adaptive simulations

In this paper, scale-adaptive simulation is used to study store trajectory variability for releases from transonic weapon bays. The scale-adaptive simulation captures the essential physics of the flow in the weapon bay, and its speed of computation allows for several trajectories to be computed within reasonable time. The results of the simulations are treated as a statistical set and a metric is put forward to decide the minimum number of simulations necessary to establish the mean and the standard deviation of the releases. Averaging the results of all trajectories was useful in developing an overall understanding of the bay pressure field role on the store trajectories. Filtering the obtained trajectories provided insight in the flow frequencies affecting the forces acting on the store and the coordinates of its center of gravity during releases. For the store employed in this study, less than one month of CPU time is needed for the complete set of simulations to be obtained, making this method promising as a further test before flight testing

Cavity flow over a transonic weapon bay during door operation

This paper considers a transonic, idealized, weapons bay. The doors are either fixed or opened in a dynamic way. The flow evolves in three stages during door opening, corresponding to closed-cavity flow, transitional flow, and (finally) open-cavity flow. The transition needs to be taken into account to design structures, as the bay wall loads are amplified, as well as the noise. The flow fluctuations are also larger than for the fully established flow. The doors limit the development of the shear layer at the early stage of the door opening

Rôle pronostic des anticorps anti-HLA en transplantation rénale : approches en population

Background : The alloimmune response induced by transplantation from a donor who differs genetically from the kidney recipient has always been the major obstacle to graft success. The present work aimed to improve characterization of kidney-allograft rejection phenotypes and identify how each one is associated with anti-HLA antibodies. We also sought to determine whether characteristics of these antibodies i.e., their levels or complementbinding ability, might play a role in kidney allograft failure. Finally, we evaluated the clinical relevance of indolent forms of ABMR and the clinical relevance of new genes expression technologies to stratify the kidney recipients at risk for failure. Methods : We used a population-based approach in precisely phenotyped cohorts of kidney recipients. The design of our study, which is based on the concomitant evaluation of immunologic and histologic data, permits a precise connection of circulating anti-HLA antibodies with a phenotype of graft injury. Findings : We identified four distinct patterns of kidney allograft rejection: T cell-mediated vascular rejection (9%), antibody-mediated vascular rejection (21%), not included in international classifications, T cell- (46%) and antibody-mediated rejection without vasculitis (24%). Risk of graft loss was 9.07 times (95CI 3.6-19.7) higher in antibody-mediated vascular rejection than in T-cell mediated rejections (p<0.0001). Patients with post-transplant complement-binding DSA had more severe graft injury phenotype with higher inflammation and increased deposition of complement fraction C4d. They have the poorest graft survival with 3.7 fold increased risk of graft loss (95CI 1.9-7.2). Subclinical ABMR is a truncated for of rejection associated with risk of kidney allograft failure. Gene expression assessment in kidney allografts with early ABMR improves classification of individuals at risk for kidney allograft loss. Conclusion : This work addresses the unmet need of the deleterious impact of anti-HLA antibodies and the improvement of risk stratification in kidney transplantation. Recognition of distinct phenotypes could lead to the development of new treatment strategies. Gene expression assessment appears useful to evaluate disease activity, disease state and prediction of failure.Contexte : La réponse allo-immune induite par la transplantation à partir d'un donneur génétiquement différent est un obstacle majeur au succès de la greffe. Notre objectif est de caractériser les différents phénotypes de rejet d'allogreffe rénale et d'identifier la façon dont chacun est associé aux anticorps anti-HLA. Nous avons également évalué l’impact de certaines propriétés de ces anticorps, comme leur intensité ou leur capacité à fixer le complément, sur l'échec des allogreffes rénales. Pour finir, nous avons étudié l’impact pronostic des formes indolentes de rejets ainsi que l’apport des nouvelles technologies d’analyses transcriptomique des biopsies de patients transplantés. Méthodes : Nous avons utilisé une approche en population, basée sur l’étude de larges cohortes de receveurs de greffes rénales. L’étude concomitante des données immunologiques et histologiques, nous a permis de corréler les caractéristiques des anticorps anti-HLA circulants aux phénotypes lésionnels. Résultats : Nous avons identifié et caractérisé 4 types distincts de rejet : les rejets vasculaires médiés par les lymphocytes T (9%) et par les anticorps (21%), non reconnus par les classifications internationales, et les rejets cellulaires (46%) et humoraux sans vascularite (24%). Le risque de perte de greffons est le plus important dans les cas de rejet vasculaire médié par anticorps. Les anticorps dirigés contre le donneur (DSA) fixant le complément induisent un phénotype histologique plus sévère, dominé par des lésions inflammatoires et plus de dépôts de la fraction C4d du complément dans les greffons. En leur présence, le risque de perte de greffons est augmenté de 3,7 fois (IC95 1,9-7,2). Les formes indolentes de rejet médié par les anticorps sont également associées à un risque accru de perte du greffon. L’utilisation d’approches moléculaires permet d’améliorer la stratification du risque au sein du groupe des patients présentant des rejets humoraux. Conclusion : Ce travail répond à un besoin clinique pressant dans le domaine de la transplantation, celui de déterminer l’impact clinique des anticorps anti-HLA et d’améliorer la stratification du risque immunologique en se basant sur leurs propriétés et l’utilisation de nouvelles technologies pour mieux caractériser l’activité et le stade des rejets humoraux

High fidelity, multi-disciplinary analysis of flow in realistic weapon bays

To improve the stealthiness, and the efficiency of military aircraft, engineers moved carried weapons from external hand points, to weapons bays. However, the flow inside bays is turbulent, and characterised by strong broadband, and tonal noise. The open bay flow leads to variability in the released store trajectory, excites the missile, and bay structures, and reduces the aircraft stealthiness. This thesis aims to improve our understanding of real weapon bay flow, and suggests a method for quantifying the store trajectory variability. The main spatio-temporal characteristics of cavity flows are described using post-processing methods, like, SPL, OASPL, and wavelet transform. Also, the code HMB3 is validated for simulation of cavity flows, comparing Scale Adaptive (SAS) results with experiments. To further improve the understanding of the physics driving this flow, a simple model is presented, and compared to experiments. The results are promising, and the model is able to reproduce the cavity flow fluctuations both in space and time. To support measurements of the noise field around a cavity flow, beamforming is applied to the CFD results. This method was able of capturing the main sources of noise around the cavity, using a microphone array, and the mean flow to simulate the propagation of acoustic waves. Also, recommendations for future use of this technique are given. Developments were carried out for this thesis, and for the first time, a CFD code is reported to simulate the complete weapon bay operation, including door operation, store release, and store aeroelasticity. The different parts of the code are strongly coupled, and work together. Thanks to new capabilities of HMB3, this thesis shows more insight on the physics behind realistic weapon bay operation. The flow establishment during door opening is described, and appears to be important for store design, only if the doors are moving very fast. Store releases are simulated, and statistical analysis of the data is performed. A statistical metric was proposed to identify the minimum number of simulations necessary for capturing the mean and standard deviation of the trajectories. Using averaged, and filtered flow data, the trajectory phases were identified and the role of the pressure field inside the cavity was clarified. In addition, the aeroelasticity of the store was computed during carriage, door opening, and release phases, showing small deformations that may lead to structural fatigue. Thanks to the efficiency of the SAS method, a large number of simulations were performed, and more than 1800 cavity travel times were simulated. Simulation of the flow around a store in a supersonic flow, and at high attitude is described in an appendix of the thesis. Like a cavity, this flow has complex features that require advanced turbulence modelling to be simulated. In addition, novel cavity flow controls are investigated, and described in a restricted appendix of the thesis

Reuse of a previously transplanted kidney: does success come with a price?

Longer wait times for deceased donor kidney transplant have prompted newer initiatives to expedite the process. Reuse of a previously transplanted kidney might be appropriate in certain circumstances. However, one must also consider the unique issues that may arise after such transplants. We describe our experience in one such case where the donor kidney had lesions of focal and segmental glomerulosclerosis and signs of alloreactivity (positive C4d staining) prior to transplantation and the recipient developed ganciclovir-resistant cytomegalovirus (CMV) infection, which was perhaps transmitted from the donor. Despite the challenges, the allograft function remained stable 5 years after reuse. © 2012 The Author. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For permissions, please email: journals.permissionsoup.com

Rôle pronostic des anticorps anti-HLA en transplantation rénale (approches en population)

Contexte : La réponse allo-immune induite par la transplantation à partir d'un donneur génétiquement différent est un obstacle majeur au succès de la greffe. Notre objectif est de caractériser les différents phénotypes de rejet d'allogreffe rénale et d'identifier la façon dont chacun est associé aux anticorps anti-HLA. Nous avons également évalué l impact de certaines propriétés de ces anticorps, comme leur intensité ou leur capacité à fixer le complément, sur l'échec des allogreffes rénales. Pour finir, nous avons étudié l impact pronostic des formes indolentes de rejets ainsi que l apport des nouvelles technologies d analyses transcriptomique des biopsies de patients transplantés. Méthodes : Nous avons utilisé une approche en population, basée sur l étude de larges cohortes de receveurs de greffes rénales. L étude concomitante des données immunologiques et histologiques, nous a permis de corréler les caractéristiques des anticorps anti-HLA circulants aux phénotypes lésionnels. Résultats : Nous avons identifié et caractérisé 4 types distincts de rejet : les rejets vasculaires médiés par les lymphocytes T (9%) et par les anticorps (21%), non reconnus par les classifications internationales, et les rejets cellulaires (46%) et humoraux sans vascularite (24%). Le risque de perte de greffons est le plus important dans les cas de rejet vasculaire médié par anticorps. Les anticorps dirigés contre le donneur (DSA) fixant le complément induisent un phénotype histologique plus sévère, dominé par des lésions inflammatoires et plus de dépôts de la fraction C4d du complément dans les greffons. En leur présence, le risque de perte de greffons est augmenté de 3,7 fois (IC95 1,9-7,2). Les formes indolentes de rejet médié par les anticorps sont également associées à un risque accru de perte du greffon. L utilisation d approches moléculaires permet d améliorer la stratification du risque au sein du groupe des patients présentant des rejets humoraux. Conclusion : Ce travail répond à un besoin clinique pressant dans le domaine de la transplantation, celui de déterminer l impact clinique des anticorps anti-HLA et d améliorer la stratification du risque immunologique en se basant sur leurs propriétés et l utilisation de nouvelles technologies pour mieux caractériser l activité et le stade des rejets humoraux.Background : The alloimmune response induced by transplantation from a donor who differs genetically from the kidney recipient has always been the major obstacle to graft success. The present work aimed to improve characterization of kidney-allograft rejection phenotypes and identify how each one is associated with anti-HLA antibodies. We also sought to determine whether characteristics of these antibodies i.e., their levels or complementbinding ability, might play a role in kidney allograft failure. Finally, we evaluated the clinical relevance of indolent forms of ABMR and the clinical relevance of new genes expression technologies to stratify the kidney recipients at risk for failure. Methods : We used a population-based approach in precisely phenotyped cohorts of kidney recipients. The design of our study, which is based on the concomitant evaluation of immunologic and histologic data, permits a precise connection of circulating anti-HLA antibodies with a phenotype of graft injury. Findings : We identified four distinct patterns of kidney allograft rejection: T cell-mediated vascular rejection (9%), antibody-mediated vascular rejection (21%), not included in international classifications, T cell- (46%) and antibody-mediated rejection without vasculitis (24%). Risk of graft loss was 9.07 times (95CI 3.6-19.7) higher in antibody-mediated vascular rejection than in T-cell mediated rejections (p<0.0001). Patients with post-transplant complement-binding DSA had more severe graft injury phenotype with higher inflammation and increased deposition of complement fraction C4d. They have the poorest graft survival with 3.7 fold increased risk of graft loss (95CI 1.9-7.2). Subclinical ABMR is a truncated for of rejection associated with risk of kidney allograft failure. Gene expression assessment in kidney allografts with early ABMR improves classification of individuals at risk for kidney allograft loss. Conclusion : This work addresses the unmet need of the deleterious impact of anti-HLA antibodies and the improvement of risk stratification in kidney transplantation. Recognition of distinct phenotypes could lead to the development of new treatment strategies. Gene expression assessment appears useful to evaluate disease activity, disease state and prediction of failure.PARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF