Radiative Transfer Modeling Developed at Onera for Numerical Simulations of Reactive Flows.

International audienceRadiative flux and power have to be calculated in many applications simulated using CFD, such as the prediction of pollutant emissions and the service life of aeroengine combustors, the design of thermal protection systems and ignition of solid propellant rocket motors, the design of spacecraft heat shields for atmospheric (re-) entries, and so on. In such configurations, the media are composed of gases (combustionproducts or plasma) and particles (soot, alumina, water droplets). Since the use of a line-by-line approach is not possible in industrial configurations, radiative properties are computed with an approximate band model. For gas radiative properties, this model is formulated either in terms of the absorption coefficient or in terms of transmissivity. To deal with any kind of problems, the Monte Carlo method has been chosen to solve the integral form of the Radiative Transfer Equation (RTE) allowing the use of the two formulations of the gas radiative property model. For media that can be dealt with using a model formulated in terms of the absorption coefficient, the Discrete Ordinates Method (DOM), that solves only the differential form of the RTE, has also been developed since it is reputed to consume less computation time than the Monte Carlo method. In this paper the fundamental relations of thermal radiation are first summarized. Then, both of the numerical methods and all the gas and particle radiative property models used at Onera to solve the RTE are described. Finally, some examples of typical applications studied at Onera with ASTRE (Monte Carlo) and REA (DOM) solvers are presented briefly

Recent CEDRE Applications

International audienceA selection of recent CEDRE applications in the aerospace field are presented to illustrate various functionalities of the code. These applications have been selected to cover a wide application field in aerodynamics, aerothermodynamics and combustion. Many of them are “multiphysics”, in the sense that they are based on the coupling of independent solvers for, respectively, gas flow, condensed phase transport, solidconduction, radiation, etc. Some of them include an external coupling to other codes.The presentation of each application includes the objectives of the computation, the methodology (modeling, numerics, grid, etc.) and some significant results

Homocysteine and cognitive impairment in Parkinson's disease: a biochemical, neuroimaging, and genetic study.

8 páginas, 1 figura, 4 tablas.The role of the plasma level of homocysteine (Hcy), as a primary outcome, and the effect of silent cerebrovascular lesions and genetic variants related to Hcy metabolism, as secondary outcomes, in the cognitive decline and dementia in Parkinson's disease (PD) were studied. This case-control study focused on 89 PD patients of minimum 10 years of evolution and older than 60 years, who were neuropsychologically classified either as cognitively normal (n = 37), having mild cognitive impairment (Petersen criteria) (n = 22), or suffering from dementia (DSM-IV) (n = 30), compared with cognitively normal age-matched control subjects (n = 30). Plasma levels of Hcy, vitamins B12 and B6, folic acid, polymorphisms in genes related to Hcy metabolism (MTHFR, MTR, MTRR, and CBS) and silent cerebrovascular events were analyzed. Plasma levels of Hcy were increased in PD patients (P = 0.0001). There were no differences between the groups of patients. The brain vascular burden was similar among PD groups. There was no association between polymorphisms in the studied genes and the Hcy plasma levels or cognitive status in PD patients. We found no evidence for a direct relationship between Hcy plasma levels and cognitive impairment and dementia in PD. No indirect effect through cerebrovascular disease or genetic background was found either.This study was partially funded by a grant from the Government of Navarra (49/2004) Spain, a research grant from Novartis Pharma (Basel, Switzerland) and by the agreement between FIMA and the ‘UTE project FIMA’. Work performed at JP-T laboratory has been funded by the Ministerio de Educación y Ciencia, Spain (SAF2006-00724).Peer reviewe